Water your willow; hibiscus not flowering; yard devoid of insects
Answers to your gardening questions from an expert in Southern Arizona.
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β I am sending two photos of my desert willow tree, now in its fourth spring. The buds form, grow and then dry out before opening. Have taken samples to Mesquite Valley. They saw no evidence of pests or disease and recommended more water and fertilizer. The leaves seem smaller, shorter than others I see. I donβt want to give up on it. Any advice?
A:Β Based on the photos, I agree with Mesquite Valley. Smaller leaf size and dropping buds and flowers are symptoms of drought. If you arenβt already doing so, make sure it gets water every two or three weeks to a depth of 24 to 36 inches during the spring, fall, and summer. Obviously, you can skip that during the monsoon season if it receives sufficient rain. These plants donβt require a lot of fertilizer so that might not be required more than once in the spring and then again in the fall.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β We are curious to know the identity of a tree we saw in a park, surviving the Southwest climate that has leaves that look like a maple and a round spiky seed pod. Can you tell us?
A:Β I am guessing you saw a sycamore tree. Sycamore trees are found across the U.S. The native variety we have in Arizona is sometimes called the Arizona sycamore (Platanus wrightii). It is also possible to find the hybrid London plane tree (PlatanusΒ x hispanica) in these parts. The Arizona native leaf shape looks more like the California native western sycamore (PlatanusΒ racemosa) and some say they are the same tree with variations due to the geographical separation between Arizona and California. The eastern American sycamore (PlatanusΒ occidentalis) more closely resembles the London plane tree in leaf shape. TMI? All these are fairly large trees for their habitats and they require lots of water to survive. In their native habitat, they are found growing near water. They are considered tough urban trees so you can find them in shopping centers but they are often stressed by the surrounding hardscape and donβt live as long as their rural relatives.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β This past year I bought a healthy hibiscus and put it in a 5-gallon pot. I watered the plant, fed it, etc. The hibiscus looks healthy but it hasnβt given me any flowers. I donβt know what I am doing wrong. I am wondering is it possible that the soil just isnβt good?
A:Β There are a few reasons why plants donβt bloom and they mostly have to do with basic needs: light, water, and soil. Make sure your plant is located in a spot where it will receive the sunlight it requires. Hibiscus is a plant that does well in the sun but not always in the desert sun. Depending on which hibiscus you planted, it might be best at an east-facing window to provide enough sun and still protect it from the intense western sun in the afternoon. This plant also requires well-drained soil so make sure your pot has a way to drain in case you add too much water. Adding fertilizer to your irrigation water will help keep the nutrients available. Containers donβt hold fertilizer as well because they require more frequent watering. Watering should be done before the soil completely dries. You can just poke around with your finger to test if the soil is still moist below the surface.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β My yard in downtown Tucson has been devoid of bees and butterflies this spring and summer, the first time in seven years here that there has been a noticeable lack of insects. There are very few to no moths or mosquitoes in the evening β outdoor lights at night illuminate no insects hovering about. Even the bat population is nonexistent because there are no bugs for the bats to eat. I am wondering if anyone else in Tucson, or near the downtown Tucson area, has noticed the lack of pollinators this year. I also wonder if any kind of municipal spraying has contributed to the lack of insects this year.
A:Β I canβt speak for everyone, but my midtown environment is loaded with insects and bats. Each area is potentially subject to a variety of influences such as irrigation, weather, available food plants, available bat habitat and pesticides. Itβs hard to say why your yard is devoid of all these creatures without more information about what is and has been going on with regard to your landscape and the surrounding area. In my conversations with the city departments that manage the municipal landscape I learned that they use very few insecticides on city property so that is not likely the reason.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β Every year at this time I have a problem with spider mites attacking my orange jubilee and torch bougainvillea. Iβve tried everything but nothing seems to stop them (except hosing them down). Any suggestions?
A:Β The hose is a good solution, especially in drier times of the year. Since mite infestations are directly proportionate to increasingly warmer and drier temperatures, it would be best to keep an eye on these plants early in the spring and knock back the populations before they get out of hand. Also be sure to maintain the overall health of the plant so it can better handle the pest pressure. Irrigate in dry weather, of course, and avoid over fertilization because the extra nitrogen makes them more attractive. In addition to the hose, infested areas can also be sprayed with insecticidal soap and horticultural oil products. During the winter or early spring control can be obtained with a dormant oil application in many cases. During the summer or growing season use a miticide or insecticidal soap. Check local stores to see whatβs for sale. Most insecticides are not effective on mites and some, especially broad-spectrum products such as carbaryl (Sevin) result in increased mite damage by killing their natural enemies. The important thing is to check the label to make sure a product is not hazardous to beneficial predators. And of course any time you use a pesticide it is important to read the label for your own safety and the safety of nontarget organisms around the area.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β I have a number of Afghan pines that have some whitish cottony stuff on the ends of many branches. Can you tell me what this is and if it is a problem?
A:Β The pine samples I collected show signs of insects in and around where the needles attach to the stem. These insects are called adelgids and they make the white, cottony material to protect them from the environment. High populations can cause yellowing, early drop of needles, drooping and dieback of terminals, and can slow the growth of trees. Vigorous plants tolerate moderate adelgid populations so the best plan is to keep your trees healthy. Appropriate watering and fertilization is important. These trees need deep watering every seven to 14 days in the summer to a depth of 24 to 36 inches. In the spring and fall, water them every 10 to 21 days and in the winter every 14 to 21 days. Avoid excess fertilization and quick-release formulations, which can promote adelgid populations. A forceful stream of water directed at the cottony masses dislodges and kills many adelgids when they are active in the spring.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β We have an infestation of fungus gnats inside our house. We have had our bug service spray the plants, the windows, everything twice. They have put granular insecticides in each plant soil twice,and even tried mosquito crystals. Then we had the two rooms containing the plants bombed. Our exterminator used PT Pro-Control Formula 2 (one can in each room). We completely sealed off the rest of the house. Two days later they were back, about 40 percent of what they were. We have a fluorescent light that has a sticky back that we were filling up nearly daily; now it takes about two days to fill. But we still have the gnats. Do you have any suggestions on how to get rid of these persistent bugs?
A:Β Fungus gnats are often found in places that are moist, have decaying plant matter, and, of course, fungus. The larvae of these flies feed on the fungus so that is where the adults lay their eggs. The management method that works best is making the habitat less inviting. With indoor plants this often means less watering to allow the soil to dry out between watering, killing off the fungus. You can also repot and lightly prune plants that seem to have a lot of decaying material and fungus present. There are products that are effective against the gnats but if you continue to provide the fungal habitat, they will be back. Sticky traps are great for monitoring your progress in reducing the population and their habitat.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β I have the weed in the attached picture growing after lots of summer monsoon weather in Tucson. Can you help me identify it?
A:Β The plant is called Coulterβs spiderling (Boerhavia coulteri) and itβs an annual in the four oβclock family (Nyctaginaceae). It can be easily found in washes and flat areas in the Sonoran Desert. I have some in my yard if you need any. It spreads like a groundcover, it produces spikes of tiny pink flowers, and it reproduces by seed. Itβs native to the Southwest and found throughout most of the state. It is especially noticeable in summer in Southern Arizona. Some call it a weed and others call it a wildflower since itβs a native. It certainly grows like a weed so you have to decide if you like it enough to keep it or dislike it enough to pull it up before it produces seed.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β We have sweet acacia trees at the entrance of a property in Chandler that are having severe limb breakage and dieback lately. It looks like borer signs and Iβm wondering if there is a good alternative tree I can recommend to the HOA board. Would a Red Push Pistache work well here? There are also a few ash trees that are showing similar signs throughout the same neighborhood. Do you think this could be caused by the same borer/pest?
A:Β The acacia tree in your photos is indeed suffering but in this case the borers are likely only a symptom rather than the cause. The holes indicate flat-headed borers and most species in this family of beetles are attracted to dead and dying trees. I recommend checking the history of irrigation practices for these trees. The species you mentioned should be receiving water every seven to 14 days during the summer to a depth of 24 to 36 inches. You can back this off to once every 10 to 21 days in the spring and fall, and every 14 to 21 days in the winter. The red push pistache is a good substitute as long as there is space for its mature size. It would likely have the same issue with irrigation if that were the problem so it would be good to address that before replanting. Since different tree species have somewhat different pests, it would be difficult to say the ash trees are having the same problem without seeing them.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β We have a very large/old saguaro in our front yard, as well as some other barrel cacti and other saguaros. About two years ago, we discovered we had the beginning of termite damage in our ceiling (attic space). We had the home treated and no problems since. The termite company said they were subterranean termites and that we may see the termites move and begin to do minimal damage to other wood outside the home. I started noticing what I believe are termite tunnels on our large saguaro. The damage became more evident later as the tunnels turned into craters left on the saguaro. The saguaro seems to be surviving. Now Iβm noticing what looks like evidence of termites in the barrel cacti. Should we be treating the termites attacking the cacti or will they cause minimal damage and move on to other sources? Are they also subterranean termites and could you recommend a treatment that would not harm the succulents?
A:Β Termites on cacti are fairly common and donβt need to be treated. Termites are only interested in the dead wood on the outside of your cacti and can coexist with these plants. They are likely desert-encrusting termites (Gnathamitermes perplexus) rather than the subterranean variety that infested your attic. Termites are categorized as decomposers and they help recycle dead plant material into soil. Itβs only when they get into our homes that we should be concerned and you already took care of that part.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β Please tell me if these yellow insects are harmless. They are multiplying fast but only on these flowers.
A:Β They arenβt harmless but in the grand scheme of things, they arenβt terrible either. Aphids as a family will suck sap from your plants and reduce their vigor. The good news is they are tiny and each one does very little damage. This species are sometimes called oleander aphids (Aphis nerii) and they prefer certain types of plants such as milkweed and oleander. A simple spray with your hose once in a while will keep the population down enough to protect your plants.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β Since there are so many fig beetles this year, I wonder if I need to treat the soil with nematodes to stop the larvae from eating my vegetable roots. What do you advise?
A:Β The fig beetle (Cotinus mutabilis), also known as figeater, June beetle, green fruit beetle, or June bug, isnβt as harmful as you might expect. The adults that are plentiful now are seeking nectar and fruit juice from wherever they can. They arenβt the best fliers and so we find them crashing into things as they search for food. I found them very entertaining while eating outside this week. Not every restaurant patron is as excited to see them though so itβs fortunate they wonβt be around for very long. They are attracted to ripe figs, as their common name suggests, although they are more likely taking advantage of holes in ripe fruit made by birds and other animals. They can be found on a wide variety of plants including fruit trees, flowering landscape plants with accessible nectar, tomatoes, and cacti. Their larvae are often found in garden compost and other decaying organic matter. They donβt feed on roots like their relatives back east so you donβt need to treat the soil to control them.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: We have this Mexican Fan Palm (I think) that faces Southwest where all our wind and rain come from. We have been told to clean off the damage because it's a home for insects and some have told us no as it protects the tree. It is a great tree protecting us from golf balls and providing morning shade to our patio. What should we do?
A: The so-called damage is really just the base of old leaves; what is left on the outside of the tree after years of fronds sloughing off as it grows. To some extent the leftover parts do protect the tree and they are a potential home for insects and birds. I like insects and birds so itβs not a problem for me. Cleaning up the tree is optional. Some people think these leaf bases add to the character of the trees and others think they look messy so itβs really your call. The tree will eventually self-clean by dropping them as it ages.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Question: Last week I discovered more than 30 dead or dying fig beetles under a desert willow that grew from seed near the foundation of my home.Β We had decided to leave the tree, and it has grown at an angle away from the home and is now about 6 years old and as tall as the house (maybe 14-16 feet).Β I picked up the beetles, but every day since there has been a similar number of dead or dying beetles. So in the past week we have had more than 200 dead beetles and dozens of dead or dying bees and wasps, mostly carpenter bees, a few blue mud daubers and various other striped bees and waspsΒ I could not identify. My first thought because of the treeβs close proximity to the house is that the pesticides that are applied every other month may have been systemic and been absorbed by the tree and put out in its nectar and pollen, especially since the bugs are all nectar drinkers and are all on their back with their legs twitching the way they do when killed by pesticides. I called the pest-control company and they insisted this was not the case. My exterminator uses bifenthrin, which according to info I can find is not systemic.Β All the info I can find seems to indicate the fig beetle mates and leaves their eggs in turf, so my thought that they were mating and reaching the end of their life cycle in my tree seems inaccurate.Β I worry about this because we were planning on putting in a raised vegetable gardenΒ in that corner of the yard.
A:Β Bifenthrin is not a systemic but rather a contact poison and an effective tool against a variety of insect pests. It will kill all of the insects you mentioned and is toxic to bees. It shouldnβt be sprayed on or near flowering plants, to protect pollinators and other nectar feeders. You will need to avoid spraying bifenthrin in a raised vegetable garden, so you might want to ask your pest-control company which pests they are seeing in that part of your yard to determine if they might be pests of your garden. While you are at it, you might evaluate the need for a regular insecticide treatment.Β Sometimes a calendar spray is recommended, but many times it is just recreational pesticide use. It really depends on the pest problem you are addressing.Make sure you know what pests they are seeing and ask them to show you specimens so you arenβt paying and spraying for no good reason.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I saw a recent post about not recommending cat claw to cover a chain-link fence because it tends to congregate at the top.Β I have the same situation. I have a chain-link fence and would like to plant vines to create a βgreenβ fence and hide the chain link. I liked the cat claw because of its low water use; itβs fast-growing and has year-round green leaves. If not cat claw, what do you recommend?Β
A:Β You are correct; the cat claw tends to clump at the top. A nice alternative is star jasmine (Trachelospermum jasminoides). This is a beautiful evergreen vine with thick, leathery, dark-green leaves and fragrant clusters of white, star-shaped flowers in great profusion each spring. Part shade is best, but it will tolerate more sun if planted in deep, well-prepared soil and watered generously. East or north exposure is desirable in low-desert areas. It can be usedΒ Β near a patio or house where the sweet fragrance can be enjoyed to the fullest. It is also effective spilling over a planter wall or billowing up a post.Β This plant spreads widely, so you donβt have to buy a lot of them unless you have a lot of fence. One every 6 to 8 feet should do it. If this description doesnβt meet your requirements or you want to see what else is available, you might check out our publication available online called βLandscape Vines for Southern Arizonaβ (AZ1606) or visit a local nurseryΒ .
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: My neighbor moved into her home last October. The prior owner was from San DiegoΒ so she had many Southern California plants in her yard. Just after our latest monsoon she noticed some plants coming up and only a day or two later one had this beautiful pink lily-type flower. The other stalks flowered in the next days and the flowers last a few days, there are no leaves. Any idea what type of plant this is?
A:Β The plants are a type of lily (Amaryllis belladonna) that are sometimes called naked ladies due to the way they flower without foliage on naked stems.Β They are native to South Africa and widely popular as a bulb.Β They are suitable for our landscapes, as they donβt require much water.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I just noticed your great pruning information in the paper, and I have a question.Β I planted this palo brea last year, in hopes that over time it would become a tallish beautiful tree that with a high arching branching pattern (surely at a minimum that we can walk under). The info you provided only addresses deciduous trees. I wonder if, when, and how to prune the branches. Also, any suggestion about staking so that it grows pretty straight up, or is that unnecessary?
A:Β The mature size of the palo brea (Parkinsonia praecox) is 20 to 30 feet tall with an even wider spread so I expect your hope for a beautiful shade tree will be realized in time. Itβs hard to tell from your photo but it appears you allowed enough space for this desert specimen to reach mature size without any restrictions.
Because it spreads so wide, it isnβt for every landscape. Pruning shouldnβt be a big deal because it has adequate space. The normal pruning we give to trees to remove damaged, crossing, and rubbing branches should be sufficient. If you need more advice on pruning, please let me know.
Staking is typically done for the first year or so if a newly planted tree requires it. Trees need to be able to sway a bit in the breeze to develop the necessary trunk flare that will support it for many years to come. Staking too tightly and for too long inhibits this development.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I recently removed a large amount of entangled vines and plants from around the back of my home. They had been there since before I purchased it in 1969.Β I would like to get rid of the roots before they start growing new sprouts so I can plant a garden. They cannot be dug out because they are really embedded into the house foundation. A friend suggested Round Up but I do not want anything toxic. I have two desert tortoises that live there, and a cat.
A:Β Roundup and similar products made with the active ingredient glyphosate are toxic to desert tortoises, among other things, so I am glad you asked before experimenting. Your best solution is the one you already used. Keeping the weeds under control by continued and persistent removal of the above ground green parts will eventually starve the plants.
Without the ability to photosynthesize, there wonβt be any food to send to the roots and eventually they will die. Unfortunately, this doesnβt happen quickly much of the time, especially if the weeds have been growing since 1969. But donβt let that discourage you. If we could put a man on the moon, we should certainly be able to kill a few weeds.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I am looking for a yellow flowering vine I can grow in a large 36-inch pot. It is south facing with late afternoon west filtered sun.Β Iβm thinking the primrose jasmine might be a good choice to grow up onto the wooden arbor we have on our south-facing arbor. What do you think?
A:Β I think you have a good idea. Primrose jasmine (Jasminum mesnyi) is a sprawling evergreen shrub that has slender arching branches 5 to 10 feet long and bright yellow double flowers 1 to 2 inches across in mid to late winter.
It develops a vine-like growth habit when branches are tied to a trellis and allowed to trail down so your arbor would work well. It makes an attractive mounding foundation plant 3 feet high if cut back once a year. It grows best in full sun or part shade and is an interesting specimen plant with graceful cascading growth habit and early flower display.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: Three years ago I bought a bonita ash tree because of its size, beauty, easy maintenance, and short period of leaf dropping.Β So impressed over the past year I was instrumental in the planting of four more in our little community. Once established how often do you feel they need to be watered?
A:Β The recommended water schedule for ash trees is once every seven to 10 days during the summer to a depth of 24 to 36 inches. In the spring and fall you can back it off to once every 10 to 21 days and in the winter every 14 to 21 days.
Also, I assume you are using drip irrigation arranged in a circular fashion around the drip line of the tree. When they are young you can get away with a hose at the base of the tree, but not once the absorbing roots extend farther out.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have an Angel Red variety pomegranate tree that is 5 years old. It is producing a very good crop of fruit this year. Iβm concerned about the care of my tree.Β Specifically, I would appreciate your advice on:
How often does it need fertilizing? Iβve been fertilizing only in the early spring.
How often should I water it in these very hot and dry conditions?
A:Β Pomegranates are tough plants that grow well in our arid conditions as long as we care for them. I recommend fertilizing once in the spring and then again in the fall. The fertilizer should be complete in that it contains equal amounts of nitrogen, phosphorus, and potassium, such as a 10-10-10 formulation. Irrigation should be provided every one to two weeks during the summer to a depth of 24 to 36 inches.
Keeping consistent irrigation throughout the growing season also helps prevent fruit from splitting. Pruning is something you do each winter to remove dead, damaged, and crossing branches. Also remove watersprouts and suckers as they appear.
Proper pruning involves removing these parts near the connection with larger branches, avoiding flush cuts and not leaving stubs either. There is more information on pruning available if you need it so please let me know. If you are okay with the natural shrubby form, this might be all you need to do. If you are trying for a tree form, there is more maintenance pruning to shape the plant and keep it that way.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I was at the garden this morning and noticed how droopy our patch of sunflowers is!Β So I took a closer look and discovered that the leaves are infested with insects! There are little white aphid looking things, and then massive sections of black dot-looking bugs, especially underneath the leaves. Maybe you can tell from the photos Iβve attached. I did my best to give them a sudsing with Dawn. Do you think this is the remedy for these bugs? Any other thoughts?
A:Β The insects on your sunflowers are called lace bugs, not to be confused with lacewings, which are beneficial predators. The black spots are likely a combination of young lace bugs, which are that color, and their poop.
Lace bugs are of the true bug order we call Hemiptera and they have piercing-sucking mouthparts just like the aphids. So they suck out the sap rather than chewing the foliage. The result of large numbers of these lace bugs feeding over a period of weeks is discoloration and the droopy look you noticed.
Fortunately, they donβt damage the flowers as much as the leaves. Insecticidal soap is a good solution as is a blast from a hose. Some dish soaps are toxic to plants so if you donβt want to spend a bit more for actual insecticidal soap, you might try spraying only part of your plant to begin just in case. These insects tend to be on the underside of the leaves at least as much as we see them on the tops so make sure you spray the plants in such a way as to cover the underside of the leaves.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to plwarren@cals.arizona.edu
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: My Arizona rosewood has some distorted leaves and fuzzy brown places at the ends of some of the distorted leaves.Β What could be causing this and what do I do about it?
A:Β The problem with your Arizona rosewood is witches broom rust called Gynosporangium vauquelinia. Rusts like this require an alternate host to complete their lifecycle.
This rust has juniper as an alternate host so there is likely an infested tree nearby or at least upwind from the rosewood. These rusts donβt kill the plants but they do reappear every year or two if the alternate host is still nearby. So you donβt need to do anything about it.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: We have a large acacia tree (the trunk is about 22 inches diameter) that is dropping leaves. We are wondering if it simply needs to be wateredΒ (though other acacia trees in the neighborhood are not getting watered and not dropping leaves). It also needs to be pruned, is there a person/company that you would recommend or can we do this ourselves?
A:Β Drought is certainly one reason trees drop leaves. I just checked the sweet acacia at our office and it is dropping leaves as well. It gets no water except rain. Desert trees like the acacia could use water every two to three weeks in the summer to a depth of 36 inches.
They can survive without for some time, but eventually they show symptoms. There are going to be differences between trees wherever you go and itβs hard to say without seeing them all what factors might be affecting these trees. Trees also lose leaves for other reasons such as pests and diseases.
If you examine some of the leaves under a magnifier you might see symptoms or signs of these potential problems. I would be glad to examine some if you want to bring them to my office. A good sample will include a small branch with some leaves still attached freshly pruned from the tree so anything living might be still attached.
Putting the sample in a zip lock bag will keep things contained until I can see them.
You can prune yourself as long as you know a little something about pruning. Itβs not rocket science but there are some basic guidelines to help you take good care of your tree.
The following link will show you a publication on pruning that should help. If you decide to hire someone instead, there is a link below to the International Society of Arboristry web site that allows you to look up local arborists to consider.
extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1139.pdf
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have a customer who is trying to identify a plant. She says it can change directions of the branching/leaves almost at will. It has leaves like a wild chive or a hesperaloe combination.
A:Β It is from the genus Kniphofia, and commonly called tritoma, red-hot poker, torch lily, knofflers, or poker plant. They are closely related to aloes, although Kniphofias donβt have very succulent leaves. There are quite a few species and cultivars of different colors. It is native to Africa. The plant has a mature height of 2 to 4 feet and a width of 3 feet. It does well in a site with full sun and well-drained soil.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: My orange tree has been very productive for 14 years but it put out small fruit last year and this year it is blooming more than a month later than usual. Is something wrong with my tree?
A:Β Both symptoms you described, small fruit and odd bloom time, are associated with lack of water. It is possible that your irrigation system needs adjusting, so that would be the first thing to check. Also we had a relatively dry late winter and early spring this year. If you reduced your irrigation for the winter as recommended and then experienced no rain in February and March, your tree was probably in need of more water. Citrus trees sometimes respond to drought conditions followed by rain with a bloom about a month later, which corresponds to the rain you had in early April.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: How likely are seriously neglected mature citrus trees to recover?
Our trees are located in central Tucson and have curling leaves, and we will not be able to water them until after May 20. They probably have not been watered (other than rain of course) since last summer.
A:Β Itβs hard to say for sure without seeing them. Curling leaves is a symptom of drought so watering soon would be good. That said, at least the leaves are still on the tree and that should give you hope. The next thing the trees will do without water is drop the leaves to reduce the amount of water escaping into the atmosphere through the leaves. Make sure that when you have the opportunity to water that you put the trees on drip irrigation arranged in a circular fashion around the drip line of the trees. The timing should be set for once every seven to 10 days now that we are experiencing the hottest and driest part of the year. Also make sure the water gets to a depth of 36 inches in the soil. You can measure this with a simple soil probe.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: Why are bees in my vegetable garden? They appear to be digging in the soil. Makes it impossible to get veggies.
A:Β Many species of solitary bees make their homes in the soil. A group called digger bees or Anthophora (meaning βflower bearerβ) are extremely common and they sometimes nest in large numbers like a community of single-family homes. Your garden is likely a good spot, according to the bees. They are not typically aggressive should you want to work around them. If you want to discourage them from nesting there, one thing you can try is using an overhead sprinkler in the area where they are nesting. Digger bees will often seek a new habitat if there is regular water raining down on their holes. Since these are also some of our native pollinators, it is good to keep them alive and nearby, if not in your garden.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I planted three Flowering Yoshino Cherry trees from pots about four years ago.Β Watered and fertilized the same for all these years. Two of the trees are doing okay. For some reason, one of the cherry trees started to drops its leaves. There is some kind of white sap coming out from the lower part of this one tree.
I do not know if the sap has anything to do with the tree dying. Do you know what might be causing the tree to look wilted and leaves to drop? This started before the high temperatures we have been getting.
A:Β Cherry trees and related fruit trees may ooze sap and drop leaves in response to injury. The injury can be due to freeze damage, insect feeding, disease, wounding from tools, hail, or sun scald of the bark. If you see any sawdust around the wound or in the sap, insects become a prime suspect.
The location of the wounds may be significant since some insects usually attack the lower trunk, others the upper branches. If you only see the cracking on the sunniest sides of the tree, the scalding is more likely.
From your photo, there doesnβt seem to be any obvious injuries from tools. If you experienced any freezing last winter or hail damage, they are possibly to blame. Please let me know if you come up with any more clues to help solve this puzzle.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have a palm tree where the frond tips are turning yellow.Β I know that the lower fronds usually turn yellow or brown due to age, but the yellowing tips are throughout the entire tree. I have not changed any watering or fertilizing schedules. Any thoughts on why this yellowing is occurring?
A:Β Frond tips turning yellow and brown are often a symptom of drought and excess salt in the soil around the roots. Fortunately, the cure for both of these is the same, more water.
A good soak once every few months will help wash the salt out of the root zone. The rest of the time these trees should be getting water every seven to 10 days in the summer, 10 to 14 days in the spring and fall, and every two to three weeks in the winter. Each time the water should reach a depth of 36 inches. With proper irrigation and an occasional soak, you will soon see how we can be good fronds for the palms.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: We have three saguaros in our front yard, two, four and 10 feet tall. All appear to be healthy. The tallest one will get only two or three blooms each year.Β Before they can open they all dry up and fall off. Do you know what would cause this? Other saguaros in the area will have buds that open up into flowers. The 10-foot saguaro was transplanted into our yard about six years ago.
A:Β Dropping flower buds are sometimes associated with environmental stress, so first Iβm curious to know if they are receiving enough irrigation. Some saguaros planted in our landscapes donβt end up in ideal locations so we might need to take better care of them than those in the wild desert.
Typically, they donβt need much water but they do need some. The recommendation is once every two weeks in the summer, every three to four weeks in the spring and fall, and none in the winter. Of course, you can skip the months where we get significant rain during the monsoon season. If you can rule out the water problem, consider what other factors in your environment could be affecting the area where they are growing.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: The attached photo, kindly sent to me by a friend who checks my house while we are away for the summer, shows my euphorbia houseplant with drooping stalks. I have been researching online, to no avail. As of a week ago, he said the plant still appeared green in color.
A:Β Euphorbias should be treated much like cactus. They need well-drained soil and can suffer from fungal diseases if left in too much water for too long. Your plant is showing signs of a vascular problem in that it cannot provide enough water pressure to keep some of the stems upright. Wilting like this can be a sign of underwatering but it can also be a sign of overwatering or disease when the stems are clogged with fungi.
If you can rule out under watering, then consider your container. From your photo, it appears the container doesnβt have a way to drain and if thatβs true, it can be part of the problem. You might try cutting off a wilted stem and look at the cross section to see if it appears to be diseased. It would likely be discolored if it were diseased.
If so, itβs possible you can cut off the infested parts and still have a surviving plant. Be sure to disinfect your pruners between cutting diseased tissue and healthy parts in case it can be spread on your tools. You can use a diluted bleach solution or rubbing alcohol solution (one part to nine parts water).
Once you cut off the diseased parts, the first thing to do is see if your plant container can be replaced with one that drains so any excess water can be diverted from the root zone. If a disease has spread to the main stem, there might not be anything to do for your plant. Time will tell.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: The leaves/stalks in the center of my desert spoon plants are being eaten away about 6 inches up from the base.Β I donβt see any problem from the base and only water them about once per month with a hose. What is causing the problem and what can I do to make them healthy again?
A:Β It appears your desert spoons are a food source for a four-legged critter, probably javelina. These animals will feed on a variety of cacti and succulents. The solution is fencing or some sort of a detour around the plants you are trying to protect. Keep up the good care you are already providing and see if you can devise some fencing system that suits your landscape plan.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have six bougainvillea plants in my back yard. I have three on the east side and three on the west side planted about a year ago.Β Last summer the ones on the west side looked great and ones on the east side looked really bad. This summer the ones on the east side look great (see picture), the ones on the west side (not shown) look really bad.
We feed them and spray for bugs but still no luck. The water system goes off every other day at 7 a.m. and 3 p.m. My wife also waters them with the hose. But we canβt seem the get them to look good at the same time. Do you have any ideas as to what we can do?
A:Β Bougainvilleas are fairly tough plants once established and by the time they are a year old they should be doing well. The trouble last summer could have been from the shock of transplanting them. The plants on the east side appear to be getting western afternoon sun. That is where they do best and your plants on that side look great.
The plants on the west side appear to be getting eastern morning sun and might be shaded in the afternoon by the wall. Since full sun is prescribed for these plants, it could be a factor for the ones that may be shaded. Itβs hard for me to say from the photos (not shown) how much shade they get but itβs something to keep in mind.
From your description, the trouble this year may be due to overfertilizing and overwatering. Once or twice each year is all you need to fertilize and watering should be done less often and deeper than your current schedule. Try switching your irrigation schedule to once every seven to 10 days to a depth of 12 to 18 inches in the summer. Then you can reduce the irrigation to once every two weeks in the fall and every three weeks in the winter.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: We have infested-with-mealybugs prickly pears on a border with a neighbor who insists that the only way to control the infestation is to use a Bayer Tree and Shrub chemical.Β I so dislike and try to avoid these solutions. Can you direct me to an online intelligent discussion that isnβt sponsored by Bayer? Or do you have a nonpoisonous alternative?
A:Β I suspect what you are seeing isnβt mealybugs but rather Cochineal scale (Dactylopious coccus) on your prickly pear cactus. The easiest treatment is spraying them with a hose. You can also use a soap solution (1 tablespoon per gallon of water).
While the Bayer product will kill these insects, it is also likely to kill beneficial insects in the area that may be feeding on the scale insects. You and your neighbor shouldnβt expect to eradicate these insects. They are very common in our area and will likely continue to feed on the cactus no matter what method you choose.
Fortunately, they arenβt likely to kill these plants if you spray them with a hose periodically.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: What are these bugs on this milkweed?
A:Β The red and black ones are milkweed bugs. That might seem like a snarky answer but itβs the official common name for these insects otherwise known as Oncopeltus fasciatus. They can also be found on oleander plants, which might explain why the yellow insects are called oleander aphids (Aphis nerii).
Both species are commonly found on milkweed and oleander plants. Insects tend to favor specific plants or plant families when they feed. Milkweed and oleander are relatives from the same plant family and known for their sap that contains cardiac glycosides, which are poisonous. The insects that ingest it as a food source are able to sequester it and become protected to some extent.
If you watch other animals preying on these insects, you may notice they spit them back out. The red and yellow coloration is natureβs way of warning predators to leave them alone but not everyone understands the warning signs without a taste test.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q:Β When your time permits,Β Would you share your thoughts on this newest visitor to the garden? He/she has increased in numbers over the past weeks and I have yet to determine which plant is part of their meal choices.
A:Β The insect, Pyropyga nigricans, is a firefly species without a light. These are predatory insects and are garden helpers so youβre lucky to have them.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have a lilac bush, which I purchased from a mail order company. It is about 12 years old, and it has never bloomed a single flower.Β It grows larger each year and has lush green foliage. I have given it fertilizer but nothing seems to help. What am I doing wrong?
A: The common lilac (Syringa vulgaris) is a favorite in many places so I understand your desire to grow them. Unfortunately, your place might not be suitable. Lack of blooms is usually related to one of six causes: the age of the plant, temperature, alternate flowering, light, nutrition, or pruning practices. In your situation, I think the likely problem is temperature. Lilacs require a certain amount of cold to trigger blooming, also known as vernalization. We don’t usually get enough cold in Southern Arizona for this plant to bloom unless you live at higher elevations. There are lilacs at the Santa Rita Experimental Range near Green Valley than have been monitored for bloom times by the USA National Phenology Network for many years. The elevation there is approximately 3,714 feet above sea level. You can check their web site for details if you are interested: usanpn.org/nn/lilacs
In downtown Tucson, where the elevation is closer to 2,389 and winter is barely recognizable, itβs too warm.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: My husband pruned two of our Mexican bird of paradise shrubs way down. Only one came back and is doing nicely.Β We have watered and used Miracle Grow fertilizer on the other one but nothing happens. Will it come back next season or do we need to replant a new one?
A:Β If you arenβt seeing any new growth by now, I suspect itβs a goner. You can scratch the surface of the branches to see if there is any green beneath. The good news is you can probably plant new ones from the seeds of the one that is doing nicely. The Mexican bird of paradise (Caesalpinia mexicana) is one of three species that grow in our area. The other two are the yellow (Caesalpinia gilliesii) and red (Caesalpinia pulcherrima) birds of paradise. A good time to prune is once blooming is finished. If you cut them too short, you risk killing them. Try just cutting back the top third next time to be safe. The flower stalks on all three species may be removed to prevent seedpods from forming and to reduce the likelihood of volunteer seedlings.Β If the pods are left on the plant to dry and split, the seeds can be thrown a surprising distance.Β The red bird of paradise dies back to ground at temperatures below freezing. It generally regrows in spring,Β from the groundΒ and the dead parts can be pruned to a few inches above the ground in late winter. Mulching the baseΒ of plantΒ in colder areas may protect the plantβs crown until spring.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I plan to buy a 15-gallon fruitless olive tree. Please tell me how much water daily or weekly it should be given once planted.Β The irrigation system in place for shrubs and trees comes on Monday and Friday for one hour. There are two black adjustable 10-gallon emitters where the tree will be planted. If the tree requires daily watering instead of the two days, I can water with a hose. When the temperature increases to 90 and higher, the irrigation system waters Monday, Wednesday, and Friday for two hours.
A:Β Olive trees should receive water every seven to 10 days in the summer to a depth of 24 to 36 inches. In the spring and fall, you can water every 10 to 14 days and in the winter, you can water every 14 to 21 days. Typically, two emitters can supply new trees as you described. As trees get older and their root zones increase in size, adding an emitter to the increasingly wider circle of drip irrigation would be appropriate every few years. The depth of irrigation can be measured with a soil probe. The schedule you are using now is watering too often and will encourage shallow root growth that will be more susceptible to our blast furnace summer heat.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: These caterpillar bugs are all over my Texas mountain laurel (the same one that had the red and black plant bugs in March β which I sprayed off with a soap solution). There are probably at least 10 groups of these caterpillars on the tree. Suggestions?
A:Β These insects are called genista caterpillars (Uresiphita reversalis) and they are commonly found throughout the southwest on Texas mountain laurels. Their damage doesnβt affect the overall health of the tree unless there are unusually high numbers of them. The damage is often only cosmetic. The same soap solution can be used against these caterpillars. Soap acts an irritant and doesnβt always completely solve the problem. You might get the same result by spraying them with a hose. The benefit of the caterpillars is they are food for birds so you could leave them there and put up with the minor damage the caterpillars cause when feeding. Other solutions include pruning off the infested ends of branches, hand-picking the caterpillars, and various insecticides labeled for use on landscape trees and shrubs. An organic solution is spraying Bt (Bacillus thuringiensis) on the leaves where they are feeding. This works best when the caterpillars are young and most susceptible to the poison. The Bt bacteria are poisonous to caterpillars but not to anything else. Since there are several strains of Bt, make sure you use the one labeled for caterpillar pests. As always, when using any pesticide it is important to read the label and follow instructions to protect you and those other non-target organisms that might be exposed to the spray. By the way, the red and black bugs (Lopidea major) you saw earlier this year are also just a minor pest that feeds on Texas mountain laurel.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed totucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have a question about compost. My neighbors have two eucalyptus trees, which shed many leaves into my yard.Β Are these good to put into the compost or not? I have concerns because of oil they may have in the leaves.
A:Β Eucalyptus leaves are fine for compost. They need to be broken down like any plant matter put into compost so that any compounds that are otherwise harmful will be neutralized. The oil that you refer to has been reported to interfere with germination in some plants but that is not something to be concerned about with composted material.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: This may be an odd question but here goes: I have an apricot tree in my yard (at least 15 years old) and it was a dwarf/ semi-dwarf when I planted it.Β I chose one that required the lowest chilling hours. I cannot remember the type or the name. It is still a reliable producer, self-pollinating and ripens in May. Do you have any guesses what the name of it could be? I think I remember the name included the word Gold.
A:Β I suspect your apricot variety is Gold Kist. This is an excellent backyard apricot for warm winter climates. Its features include very good quality, freestone fruit, and it is heavy bearing. It is an early harvest variety, from late May to early June. It requires 300 chill hours and is self-fruitful.
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have a question related to the βDesert Museumβ palo verde.
I want to plant this tree at our house, but I am a little wary because of the threat of palo verde beetles getting to the roots and killing it prematurely. Perhaps you can help me assess this risk?
A:Β The main risk for these beetles is an unhealthy tree. The palo verde beetle is endemic to this area and there is little to be done to a tree that has been infested. They are known to attack stressed trees so the best prevention is to keep trees as healthy as possible. This is primarily accomplished by providing proper irrigation and pruning. Since these are native desert trees they can survive on rainwater but when we have drier conditions than usual, supplemental water can help. Typically for desert trees this means installing drip irrigation around the tree at the drip line and providing deep watering to a depth of 24 to 36 inches every 14 to 21 days in the spring, summer, and fall. In the winter you can skip the irrigation, assuming we have normal winter rains. Proper pruning when the tree is young will result in a mature tree that is structurally stronger, lives longer, and is less costly to maintain. Donβt be in a hurry to prune at planting. A newly planted young tree should be given a chance to put down roots before taking any branches off unless they were damaged in the planting process. After a year or so it will be time to structurally prune your tree to ensure its long-term health.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: This year, we have some peaches with dimples. The fruit is rotten inside. Could it be a plant pathogen of some kind?
A:Β The short answer is yes. Your peaches are likely suffering from a pathogen as a result of insect feeding damage. The prime suspect in this case is the leaf-footed bug. These insects have piercing-sucking mouthparts and while feeding on young developing fruit leave scars that are known as cat-facing and sometimes this feeding activity will introduce fungi that may cause the rot.
Leaf-footed bugs are common in our area and may feed on a variety of plants including pomegranate, pecan, citrus, and peaches. They are difficult to manage once in the adult stage because they can fly and move about quickly.
There are insecticides available, but they are only effective on the young bugs. These insecticides are harmful to bees, so take care to avoid spraying plants in bloom. Monitoring for and removing egg masses in the early spring is another tactic that is potentially more successful if you are persistently looking in the spring when eggs are laid and young bugs are emerging from them.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: What is going on with my rosemary bush? Two days ago I looked at the bush and discovered damage.
A:Β Rosemary (Rosmarinus officinalis) is a shrub that grows well in the desert. The natural form is shaggier than the sheared version you have growing. The damage you are seeing is likely a result of regular shearing of the foliage. Often shearing creates a shell of green that prevents light from entering the inner parts of the plant. Eventually dead spots will occur and regrowth from those branches will not likely happen. A better treatment would be less frequent light pruning as necessary and in a more selective fashion to allow the plant to achieve its natural form and to open up the plant a bit to light, air, and water.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: We have 30-year-old Rhaphiolepis indica planted in a slightly raised planter.Β One side was particularly hit hard by the freeze a few years ago (17 degrees in Tucson in February), or so we thought, until we caught a couple of deer munching on that particular shrub. It never recovered from the munching. The shrubs on the other side of the planter were doing well until four deer became emboldened and began munching on the flowers and new leaf growth on the other side near our front gate. Those plants, too, have stopped putting on new leaves and weeks later look exactly like the deer left them. What can we do to rejuvenate the plants/encourage them to grow again?
A:Β Deer munching is definitely a hazard for Rhaphiolepis indica (Indian hawthorn), so some sort of fencing or detours around your shrub are required before you spend a lot of time on rejuvenation.
The best time to prune is around May or when it is finished blooming. You can selectively prune out the damaged branches where deer were feeding. From your photo the shrub looks pretty full and selective pruning should help open it up to more light, air, and water as well. Otherwise, continue to provide sufficient water, fertilize annually and monitor deer activity as needed.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.comΒ
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I am sending two photos of my desert willow tree, now in its fourth spring. The buds form, grow and then dry out before opening.Β Have taken samples to Mesquite Valley Growers. They see no evidence of pests or disease, and recommended more water and fertilizer. The leaves seem smaller and shorter than others I see.
A:Β I agree with Mesquite Valley Growers; the symptoms you describe are likely related to insufficient watering. The recommended schedule for desert trees is once every two to three weeks in the spring, summer, and fall to a depth of 24 to 36 inches. An annual spring fertilizer application wouldnβt hurt either, making sure the fertilizer is watered in to reach the absorbing roots.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I purchased this sugar bush at Desert Survivors Native Plant Nursery two years ago. It chronically looks like it isnβt getting enough water; there are dry, brown leaves. It is planted in desert soil with a cactus mix amendment. It is on a shrub line that runs twice a week right now, for 2Β½Β hours. I have played with the emitter flow and am putting about 20 gallons each application. It gets sun until about 3 p.m. Is there anything I can do to help it thrive?
A:Β Sugar bush (Rhus ovata) is a moderate water user but twice per week at 20 gallons each application seems like a lot of water for a native shrub. If you arenβt checking to see how deep the water is going, I suggest using a soil probe to determine the depth of the watering. Ideally, water should reach a depth of 24 to 36 inches. I recommend backing off your irrigation to once a week for the summer and once every two weeks in the spring and fall.
Overwatering sometimes shows similar symptoms to underwatering, so looks can be deceiving.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- Updated
Click the photo below to read more gardening tips. This includes βSaguaro surgery; ocotillo - dead or alive?; blood oranges"
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β I am sending two photos of my desert willow tree, now in its fourth spring. The buds form, grow and then dry out before opening. Have taken samples to Mesquite Valley. They saw no evidence of pests or disease and recommended more water and fertilizer. The leaves seem smaller, shorter than others I see. I donβt want to give up on it. Any advice?
A:Β Based on the photos, I agree with Mesquite Valley. Smaller leaf size and dropping buds and flowers are symptoms of drought. If you arenβt already doing so, make sure it gets water every two or three weeks to a depth of 24 to 36 inches during the spring, fall, and summer. Obviously, you can skip that during the monsoon season if it receives sufficient rain. These plants donβt require a lot of fertilizer so that might not be required more than once in the spring and then again in the fall.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β We are curious to know the identity of a tree we saw in a park, surviving the Southwest climate that has leaves that look like a maple and a round spiky seed pod. Can you tell us?
A:Β I am guessing you saw a sycamore tree. Sycamore trees are found across the U.S. The native variety we have in Arizona is sometimes called the Arizona sycamore (Platanus wrightii). It is also possible to find the hybrid London plane tree (PlatanusΒ x hispanica) in these parts. The Arizona native leaf shape looks more like the California native western sycamore (PlatanusΒ racemosa) and some say they are the same tree with variations due to the geographical separation between Arizona and California. The eastern American sycamore (PlatanusΒ occidentalis) more closely resembles the London plane tree in leaf shape. TMI? All these are fairly large trees for their habitats and they require lots of water to survive. In their native habitat, they are found growing near water. They are considered tough urban trees so you can find them in shopping centers but they are often stressed by the surrounding hardscape and donβt live as long as their rural relatives.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β This past year I bought a healthy hibiscus and put it in a 5-gallon pot. I watered the plant, fed it, etc. The hibiscus looks healthy but it hasnβt given me any flowers. I donβt know what I am doing wrong. I am wondering is it possible that the soil just isnβt good?
A:Β There are a few reasons why plants donβt bloom and they mostly have to do with basic needs: light, water, and soil. Make sure your plant is located in a spot where it will receive the sunlight it requires. Hibiscus is a plant that does well in the sun but not always in the desert sun. Depending on which hibiscus you planted, it might be best at an east-facing window to provide enough sun and still protect it from the intense western sun in the afternoon. This plant also requires well-drained soil so make sure your pot has a way to drain in case you add too much water. Adding fertilizer to your irrigation water will help keep the nutrients available. Containers donβt hold fertilizer as well because they require more frequent watering. Watering should be done before the soil completely dries. You can just poke around with your finger to test if the soil is still moist below the surface.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β My yard in downtown Tucson has been devoid of bees and butterflies this spring and summer, the first time in seven years here that there has been a noticeable lack of insects. There are very few to no moths or mosquitoes in the evening β outdoor lights at night illuminate no insects hovering about. Even the bat population is nonexistent because there are no bugs for the bats to eat. I am wondering if anyone else in Tucson, or near the downtown Tucson area, has noticed the lack of pollinators this year. I also wonder if any kind of municipal spraying has contributed to the lack of insects this year.
A:Β I canβt speak for everyone, but my midtown environment is loaded with insects and bats. Each area is potentially subject to a variety of influences such as irrigation, weather, available food plants, available bat habitat and pesticides. Itβs hard to say why your yard is devoid of all these creatures without more information about what is and has been going on with regard to your landscape and the surrounding area. In my conversations with the city departments that manage the municipal landscape I learned that they use very few insecticides on city property so that is not likely the reason.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β Every year at this time I have a problem with spider mites attacking my orange jubilee and torch bougainvillea. Iβve tried everything but nothing seems to stop them (except hosing them down). Any suggestions?
A:Β The hose is a good solution, especially in drier times of the year. Since mite infestations are directly proportionate to increasingly warmer and drier temperatures, it would be best to keep an eye on these plants early in the spring and knock back the populations before they get out of hand. Also be sure to maintain the overall health of the plant so it can better handle the pest pressure. Irrigate in dry weather, of course, and avoid over fertilization because the extra nitrogen makes them more attractive. In addition to the hose, infested areas can also be sprayed with insecticidal soap and horticultural oil products. During the winter or early spring control can be obtained with a dormant oil application in many cases. During the summer or growing season use a miticide or insecticidal soap. Check local stores to see whatβs for sale. Most insecticides are not effective on mites and some, especially broad-spectrum products such as carbaryl (Sevin) result in increased mite damage by killing their natural enemies. The important thing is to check the label to make sure a product is not hazardous to beneficial predators. And of course any time you use a pesticide it is important to read the label for your own safety and the safety of nontarget organisms around the area.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β I have a number of Afghan pines that have some whitish cottony stuff on the ends of many branches. Can you tell me what this is and if it is a problem?
A:Β The pine samples I collected show signs of insects in and around where the needles attach to the stem. These insects are called adelgids and they make the white, cottony material to protect them from the environment. High populations can cause yellowing, early drop of needles, drooping and dieback of terminals, and can slow the growth of trees. Vigorous plants tolerate moderate adelgid populations so the best plan is to keep your trees healthy. Appropriate watering and fertilization is important. These trees need deep watering every seven to 14 days in the summer to a depth of 24 to 36 inches. In the spring and fall, water them every 10 to 21 days and in the winter every 14 to 21 days. Avoid excess fertilization and quick-release formulations, which can promote adelgid populations. A forceful stream of water directed at the cottony masses dislodges and kills many adelgids when they are active in the spring.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β We have an infestation of fungus gnats inside our house. We have had our bug service spray the plants, the windows, everything twice. They have put granular insecticides in each plant soil twice,and even tried mosquito crystals. Then we had the two rooms containing the plants bombed. Our exterminator used PT Pro-Control Formula 2 (one can in each room). We completely sealed off the rest of the house. Two days later they were back, about 40 percent of what they were. We have a fluorescent light that has a sticky back that we were filling up nearly daily; now it takes about two days to fill. But we still have the gnats. Do you have any suggestions on how to get rid of these persistent bugs?
A:Β Fungus gnats are often found in places that are moist, have decaying plant matter, and, of course, fungus. The larvae of these flies feed on the fungus so that is where the adults lay their eggs. The management method that works best is making the habitat less inviting. With indoor plants this often means less watering to allow the soil to dry out between watering, killing off the fungus. You can also repot and lightly prune plants that seem to have a lot of decaying material and fungus present. There are products that are effective against the gnats but if you continue to provide the fungal habitat, they will be back. Sticky traps are great for monitoring your progress in reducing the population and their habitat.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β I have the weed in the attached picture growing after lots of summer monsoon weather in Tucson. Can you help me identify it?
A:Β The plant is called Coulterβs spiderling (Boerhavia coulteri) and itβs an annual in the four oβclock family (Nyctaginaceae). It can be easily found in washes and flat areas in the Sonoran Desert. I have some in my yard if you need any. It spreads like a groundcover, it produces spikes of tiny pink flowers, and it reproduces by seed. Itβs native to the Southwest and found throughout most of the state. It is especially noticeable in summer in Southern Arizona. Some call it a weed and others call it a wildflower since itβs a native. It certainly grows like a weed so you have to decide if you like it enough to keep it or dislike it enough to pull it up before it produces seed.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β We have sweet acacia trees at the entrance of a property in Chandler that are having severe limb breakage and dieback lately. It looks like borer signs and Iβm wondering if there is a good alternative tree I can recommend to the HOA board. Would a Red Push Pistache work well here? There are also a few ash trees that are showing similar signs throughout the same neighborhood. Do you think this could be caused by the same borer/pest?
A:Β The acacia tree in your photos is indeed suffering but in this case the borers are likely only a symptom rather than the cause. The holes indicate flat-headed borers and most species in this family of beetles are attracted to dead and dying trees. I recommend checking the history of irrigation practices for these trees. The species you mentioned should be receiving water every seven to 14 days during the summer to a depth of 24 to 36 inches. You can back this off to once every 10 to 21 days in the spring and fall, and every 14 to 21 days in the winter. The red push pistache is a good substitute as long as there is space for its mature size. It would likely have the same issue with irrigation if that were the problem so it would be good to address that before replanting. Since different tree species have somewhat different pests, it would be difficult to say the ash trees are having the same problem without seeing them.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β We have a very large/old saguaro in our front yard, as well as some other barrel cacti and other saguaros. About two years ago, we discovered we had the beginning of termite damage in our ceiling (attic space). We had the home treated and no problems since. The termite company said they were subterranean termites and that we may see the termites move and begin to do minimal damage to other wood outside the home. I started noticing what I believe are termite tunnels on our large saguaro. The damage became more evident later as the tunnels turned into craters left on the saguaro. The saguaro seems to be surviving. Now Iβm noticing what looks like evidence of termites in the barrel cacti. Should we be treating the termites attacking the cacti or will they cause minimal damage and move on to other sources? Are they also subterranean termites and could you recommend a treatment that would not harm the succulents?
A:Β Termites on cacti are fairly common and donβt need to be treated. Termites are only interested in the dead wood on the outside of your cacti and can coexist with these plants. They are likely desert-encrusting termites (Gnathamitermes perplexus) rather than the subterranean variety that infested your attic. Termites are categorized as decomposers and they help recycle dead plant material into soil. Itβs only when they get into our homes that we should be concerned and you already took care of that part.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β Please tell me if these yellow insects are harmless. They are multiplying fast but only on these flowers.
A:Β They arenβt harmless but in the grand scheme of things, they arenβt terrible either. Aphids as a family will suck sap from your plants and reduce their vigor. The good news is they are tiny and each one does very little damage. This species are sometimes called oleander aphids (Aphis nerii) and they prefer certain types of plants such as milkweed and oleander. A simple spray with your hose once in a while will keep the population down enough to protect your plants.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β Since there are so many fig beetles this year, I wonder if I need to treat the soil with nematodes to stop the larvae from eating my vegetable roots. What do you advise?
A:Β The fig beetle (Cotinus mutabilis), also known as figeater, June beetle, green fruit beetle, or June bug, isnβt as harmful as you might expect. The adults that are plentiful now are seeking nectar and fruit juice from wherever they can. They arenβt the best fliers and so we find them crashing into things as they search for food. I found them very entertaining while eating outside this week. Not every restaurant patron is as excited to see them though so itβs fortunate they wonβt be around for very long. They are attracted to ripe figs, as their common name suggests, although they are more likely taking advantage of holes in ripe fruit made by birds and other animals. They can be found on a wide variety of plants including fruit trees, flowering landscape plants with accessible nectar, tomatoes, and cacti. Their larvae are often found in garden compost and other decaying organic matter. They donβt feed on roots like their relatives back east so you donβt need to treat the soil to control them.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: We have this Mexican Fan Palm (I think) that faces Southwest where all our wind and rain come from. We have been told to clean off the damage because it's a home for insects and some have told us no as it protects the tree. It is a great tree protecting us from golf balls and providing morning shade to our patio. What should we do?
A: The so-called damage is really just the base of old leaves; what is left on the outside of the tree after years of fronds sloughing off as it grows. To some extent the leftover parts do protect the tree and they are a potential home for insects and birds. I like insects and birds so itβs not a problem for me. Cleaning up the tree is optional. Some people think these leaf bases add to the character of the trees and others think they look messy so itβs really your call. The tree will eventually self-clean by dropping them as it ages.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Question: Last week I discovered more than 30 dead or dying fig beetles under a desert willow that grew from seed near the foundation of my home.Β We had decided to leave the tree, and it has grown at an angle away from the home and is now about 6 years old and as tall as the house (maybe 14-16 feet).Β I picked up the beetles, but every day since there has been a similar number of dead or dying beetles. So in the past week we have had more than 200 dead beetles and dozens of dead or dying bees and wasps, mostly carpenter bees, a few blue mud daubers and various other striped bees and waspsΒ I could not identify. My first thought because of the treeβs close proximity to the house is that the pesticides that are applied every other month may have been systemic and been absorbed by the tree and put out in its nectar and pollen, especially since the bugs are all nectar drinkers and are all on their back with their legs twitching the way they do when killed by pesticides. I called the pest-control company and they insisted this was not the case. My exterminator uses bifenthrin, which according to info I can find is not systemic.Β All the info I can find seems to indicate the fig beetle mates and leaves their eggs in turf, so my thought that they were mating and reaching the end of their life cycle in my tree seems inaccurate.Β I worry about this because we were planning on putting in a raised vegetable gardenΒ in that corner of the yard.
A:Β Bifenthrin is not a systemic but rather a contact poison and an effective tool against a variety of insect pests. It will kill all of the insects you mentioned and is toxic to bees. It shouldnβt be sprayed on or near flowering plants, to protect pollinators and other nectar feeders. You will need to avoid spraying bifenthrin in a raised vegetable garden, so you might want to ask your pest-control company which pests they are seeing in that part of your yard to determine if they might be pests of your garden. While you are at it, you might evaluate the need for a regular insecticide treatment.Β Sometimes a calendar spray is recommended, but many times it is just recreational pesticide use. It really depends on the pest problem you are addressing.Make sure you know what pests they are seeing and ask them to show you specimens so you arenβt paying and spraying for no good reason.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I saw a recent post about not recommending cat claw to cover a chain-link fence because it tends to congregate at the top.Β I have the same situation. I have a chain-link fence and would like to plant vines to create a βgreenβ fence and hide the chain link. I liked the cat claw because of its low water use; itβs fast-growing and has year-round green leaves. If not cat claw, what do you recommend?Β
A:Β You are correct; the cat claw tends to clump at the top. A nice alternative is star jasmine (Trachelospermum jasminoides). This is a beautiful evergreen vine with thick, leathery, dark-green leaves and fragrant clusters of white, star-shaped flowers in great profusion each spring. Part shade is best, but it will tolerate more sun if planted in deep, well-prepared soil and watered generously. East or north exposure is desirable in low-desert areas. It can be usedΒ Β near a patio or house where the sweet fragrance can be enjoyed to the fullest. It is also effective spilling over a planter wall or billowing up a post.Β This plant spreads widely, so you donβt have to buy a lot of them unless you have a lot of fence. One every 6 to 8 feet should do it. If this description doesnβt meet your requirements or you want to see what else is available, you might check out our publication available online called βLandscape Vines for Southern Arizonaβ (AZ1606) or visit a local nurseryΒ .
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: My neighbor moved into her home last October. The prior owner was from San DiegoΒ so she had many Southern California plants in her yard. Just after our latest monsoon she noticed some plants coming up and only a day or two later one had this beautiful pink lily-type flower. The other stalks flowered in the next days and the flowers last a few days, there are no leaves. Any idea what type of plant this is?
A:Β The plants are a type of lily (Amaryllis belladonna) that are sometimes called naked ladies due to the way they flower without foliage on naked stems.Β They are native to South Africa and widely popular as a bulb.Β They are suitable for our landscapes, as they donβt require much water.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I just noticed your great pruning information in the paper, and I have a question.Β I planted this palo brea last year, in hopes that over time it would become a tallish beautiful tree that with a high arching branching pattern (surely at a minimum that we can walk under). The info you provided only addresses deciduous trees. I wonder if, when, and how to prune the branches. Also, any suggestion about staking so that it grows pretty straight up, or is that unnecessary?
A:Β The mature size of the palo brea (Parkinsonia praecox) is 20 to 30 feet tall with an even wider spread so I expect your hope for a beautiful shade tree will be realized in time. Itβs hard to tell from your photo but it appears you allowed enough space for this desert specimen to reach mature size without any restrictions.
Because it spreads so wide, it isnβt for every landscape. Pruning shouldnβt be a big deal because it has adequate space. The normal pruning we give to trees to remove damaged, crossing, and rubbing branches should be sufficient. If you need more advice on pruning, please let me know.
Staking is typically done for the first year or so if a newly planted tree requires it. Trees need to be able to sway a bit in the breeze to develop the necessary trunk flare that will support it for many years to come. Staking too tightly and for too long inhibits this development.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I recently removed a large amount of entangled vines and plants from around the back of my home. They had been there since before I purchased it in 1969.Β I would like to get rid of the roots before they start growing new sprouts so I can plant a garden. They cannot be dug out because they are really embedded into the house foundation. A friend suggested Round Up but I do not want anything toxic. I have two desert tortoises that live there, and a cat.
A:Β Roundup and similar products made with the active ingredient glyphosate are toxic to desert tortoises, among other things, so I am glad you asked before experimenting. Your best solution is the one you already used. Keeping the weeds under control by continued and persistent removal of the above ground green parts will eventually starve the plants.
Without the ability to photosynthesize, there wonβt be any food to send to the roots and eventually they will die. Unfortunately, this doesnβt happen quickly much of the time, especially if the weeds have been growing since 1969. But donβt let that discourage you. If we could put a man on the moon, we should certainly be able to kill a few weeds.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I am looking for a yellow flowering vine I can grow in a large 36-inch pot. It is south facing with late afternoon west filtered sun.Β Iβm thinking the primrose jasmine might be a good choice to grow up onto the wooden arbor we have on our south-facing arbor. What do you think?
A:Β I think you have a good idea. Primrose jasmine (Jasminum mesnyi) is a sprawling evergreen shrub that has slender arching branches 5 to 10 feet long and bright yellow double flowers 1 to 2 inches across in mid to late winter.
It develops a vine-like growth habit when branches are tied to a trellis and allowed to trail down so your arbor would work well. It makes an attractive mounding foundation plant 3 feet high if cut back once a year. It grows best in full sun or part shade and is an interesting specimen plant with graceful cascading growth habit and early flower display.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: Three years ago I bought a bonita ash tree because of its size, beauty, easy maintenance, and short period of leaf dropping.Β So impressed over the past year I was instrumental in the planting of four more in our little community. Once established how often do you feel they need to be watered?
A:Β The recommended water schedule for ash trees is once every seven to 10 days during the summer to a depth of 24 to 36 inches. In the spring and fall you can back it off to once every 10 to 21 days and in the winter every 14 to 21 days.
Also, I assume you are using drip irrigation arranged in a circular fashion around the drip line of the tree. When they are young you can get away with a hose at the base of the tree, but not once the absorbing roots extend farther out.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have an Angel Red variety pomegranate tree that is 5 years old. It is producing a very good crop of fruit this year. Iβm concerned about the care of my tree.Β Specifically, I would appreciate your advice on:
How often does it need fertilizing? Iβve been fertilizing only in the early spring.
How often should I water it in these very hot and dry conditions?
A:Β Pomegranates are tough plants that grow well in our arid conditions as long as we care for them. I recommend fertilizing once in the spring and then again in the fall. The fertilizer should be complete in that it contains equal amounts of nitrogen, phosphorus, and potassium, such as a 10-10-10 formulation. Irrigation should be provided every one to two weeks during the summer to a depth of 24 to 36 inches.
Keeping consistent irrigation throughout the growing season also helps prevent fruit from splitting. Pruning is something you do each winter to remove dead, damaged, and crossing branches. Also remove watersprouts and suckers as they appear.
Proper pruning involves removing these parts near the connection with larger branches, avoiding flush cuts and not leaving stubs either. There is more information on pruning available if you need it so please let me know. If you are okay with the natural shrubby form, this might be all you need to do. If you are trying for a tree form, there is more maintenance pruning to shape the plant and keep it that way.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: I was at the garden this morning and noticed how droopy our patch of sunflowers is!Β So I took a closer look and discovered that the leaves are infested with insects! There are little white aphid looking things, and then massive sections of black dot-looking bugs, especially underneath the leaves. Maybe you can tell from the photos Iβve attached. I did my best to give them a sudsing with Dawn. Do you think this is the remedy for these bugs? Any other thoughts?
A:Β The insects on your sunflowers are called lace bugs, not to be confused with lacewings, which are beneficial predators. The black spots are likely a combination of young lace bugs, which are that color, and their poop.
Lace bugs are of the true bug order we call Hemiptera and they have piercing-sucking mouthparts just like the aphids. So they suck out the sap rather than chewing the foliage. The result of large numbers of these lace bugs feeding over a period of weeks is discoloration and the droopy look you noticed.
Fortunately, they donβt damage the flowers as much as the leaves. Insecticidal soap is a good solution as is a blast from a hose. Some dish soaps are toxic to plants so if you donβt want to spend a bit more for actual insecticidal soap, you might try spraying only part of your plant to begin just in case. These insects tend to be on the underside of the leaves at least as much as we see them on the tops so make sure you spray the plants in such a way as to cover the underside of the leaves.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to plwarren@cals.arizona.edu
- By Peter L. Warren Special to the Arizona Daily Star
Q: My Arizona rosewood has some distorted leaves and fuzzy brown places at the ends of some of the distorted leaves.Β What could be causing this and what do I do about it?
A:Β The problem with your Arizona rosewood is witches broom rust called Gynosporangium vauquelinia. Rusts like this require an alternate host to complete their lifecycle.
This rust has juniper as an alternate host so there is likely an infested tree nearby or at least upwind from the rosewood. These rusts donβt kill the plants but they do reappear every year or two if the alternate host is still nearby. So you donβt need to do anything about it.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: We have a large acacia tree (the trunk is about 22 inches diameter) that is dropping leaves. We are wondering if it simply needs to be wateredΒ (though other acacia trees in the neighborhood are not getting watered and not dropping leaves). It also needs to be pruned, is there a person/company that you would recommend or can we do this ourselves?
A:Β Drought is certainly one reason trees drop leaves. I just checked the sweet acacia at our office and it is dropping leaves as well. It gets no water except rain. Desert trees like the acacia could use water every two to three weeks in the summer to a depth of 36 inches.
They can survive without for some time, but eventually they show symptoms. There are going to be differences between trees wherever you go and itβs hard to say without seeing them all what factors might be affecting these trees. Trees also lose leaves for other reasons such as pests and diseases.
If you examine some of the leaves under a magnifier you might see symptoms or signs of these potential problems. I would be glad to examine some if you want to bring them to my office. A good sample will include a small branch with some leaves still attached freshly pruned from the tree so anything living might be still attached.
Putting the sample in a zip lock bag will keep things contained until I can see them.
You can prune yourself as long as you know a little something about pruning. Itβs not rocket science but there are some basic guidelines to help you take good care of your tree.
The following link will show you a publication on pruning that should help. If you decide to hire someone instead, there is a link below to the International Society of Arboristry web site that allows you to look up local arborists to consider.
extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1139.pdf
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have a customer who is trying to identify a plant. She says it can change directions of the branching/leaves almost at will. It has leaves like a wild chive or a hesperaloe combination.
A:Β It is from the genus Kniphofia, and commonly called tritoma, red-hot poker, torch lily, knofflers, or poker plant. They are closely related to aloes, although Kniphofias donβt have very succulent leaves. There are quite a few species and cultivars of different colors. It is native to Africa. The plant has a mature height of 2 to 4 feet and a width of 3 feet. It does well in a site with full sun and well-drained soil.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: My orange tree has been very productive for 14 years but it put out small fruit last year and this year it is blooming more than a month later than usual. Is something wrong with my tree?
A:Β Both symptoms you described, small fruit and odd bloom time, are associated with lack of water. It is possible that your irrigation system needs adjusting, so that would be the first thing to check. Also we had a relatively dry late winter and early spring this year. If you reduced your irrigation for the winter as recommended and then experienced no rain in February and March, your tree was probably in need of more water. Citrus trees sometimes respond to drought conditions followed by rain with a bloom about a month later, which corresponds to the rain you had in early April.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: How likely are seriously neglected mature citrus trees to recover?
Our trees are located in central Tucson and have curling leaves, and we will not be able to water them until after May 20. They probably have not been watered (other than rain of course) since last summer.
A:Β Itβs hard to say for sure without seeing them. Curling leaves is a symptom of drought so watering soon would be good. That said, at least the leaves are still on the tree and that should give you hope. The next thing the trees will do without water is drop the leaves to reduce the amount of water escaping into the atmosphere through the leaves. Make sure that when you have the opportunity to water that you put the trees on drip irrigation arranged in a circular fashion around the drip line of the trees. The timing should be set for once every seven to 10 days now that we are experiencing the hottest and driest part of the year. Also make sure the water gets to a depth of 36 inches in the soil. You can measure this with a simple soil probe.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: Why are bees in my vegetable garden? They appear to be digging in the soil. Makes it impossible to get veggies.
A:Β Many species of solitary bees make their homes in the soil. A group called digger bees or Anthophora (meaning βflower bearerβ) are extremely common and they sometimes nest in large numbers like a community of single-family homes. Your garden is likely a good spot, according to the bees. They are not typically aggressive should you want to work around them. If you want to discourage them from nesting there, one thing you can try is using an overhead sprinkler in the area where they are nesting. Digger bees will often seek a new habitat if there is regular water raining down on their holes. Since these are also some of our native pollinators, it is good to keep them alive and nearby, if not in your garden.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I planted three Flowering Yoshino Cherry trees from pots about four years ago.Β Watered and fertilized the same for all these years. Two of the trees are doing okay. For some reason, one of the cherry trees started to drops its leaves. There is some kind of white sap coming out from the lower part of this one tree.
I do not know if the sap has anything to do with the tree dying. Do you know what might be causing the tree to look wilted and leaves to drop? This started before the high temperatures we have been getting.
A:Β Cherry trees and related fruit trees may ooze sap and drop leaves in response to injury. The injury can be due to freeze damage, insect feeding, disease, wounding from tools, hail, or sun scald of the bark. If you see any sawdust around the wound or in the sap, insects become a prime suspect.
The location of the wounds may be significant since some insects usually attack the lower trunk, others the upper branches. If you only see the cracking on the sunniest sides of the tree, the scalding is more likely.
From your photo, there doesnβt seem to be any obvious injuries from tools. If you experienced any freezing last winter or hail damage, they are possibly to blame. Please let me know if you come up with any more clues to help solve this puzzle.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have a palm tree where the frond tips are turning yellow.Β I know that the lower fronds usually turn yellow or brown due to age, but the yellowing tips are throughout the entire tree. I have not changed any watering or fertilizing schedules. Any thoughts on why this yellowing is occurring?
A:Β Frond tips turning yellow and brown are often a symptom of drought and excess salt in the soil around the roots. Fortunately, the cure for both of these is the same, more water.
A good soak once every few months will help wash the salt out of the root zone. The rest of the time these trees should be getting water every seven to 10 days in the summer, 10 to 14 days in the spring and fall, and every two to three weeks in the winter. Each time the water should reach a depth of 36 inches. With proper irrigation and an occasional soak, you will soon see how we can be good fronds for the palms.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: We have three saguaros in our front yard, two, four and 10 feet tall. All appear to be healthy. The tallest one will get only two or three blooms each year.Β Before they can open they all dry up and fall off. Do you know what would cause this? Other saguaros in the area will have buds that open up into flowers. The 10-foot saguaro was transplanted into our yard about six years ago.
A:Β Dropping flower buds are sometimes associated with environmental stress, so first Iβm curious to know if they are receiving enough irrigation. Some saguaros planted in our landscapes donβt end up in ideal locations so we might need to take better care of them than those in the wild desert.
Typically, they donβt need much water but they do need some. The recommendation is once every two weeks in the summer, every three to four weeks in the spring and fall, and none in the winter. Of course, you can skip the months where we get significant rain during the monsoon season. If you can rule out the water problem, consider what other factors in your environment could be affecting the area where they are growing.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: The attached photo, kindly sent to me by a friend who checks my house while we are away for the summer, shows my euphorbia houseplant with drooping stalks. I have been researching online, to no avail. As of a week ago, he said the plant still appeared green in color.
A:Β Euphorbias should be treated much like cactus. They need well-drained soil and can suffer from fungal diseases if left in too much water for too long. Your plant is showing signs of a vascular problem in that it cannot provide enough water pressure to keep some of the stems upright. Wilting like this can be a sign of underwatering but it can also be a sign of overwatering or disease when the stems are clogged with fungi.
If you can rule out under watering, then consider your container. From your photo, it appears the container doesnβt have a way to drain and if thatβs true, it can be part of the problem. You might try cutting off a wilted stem and look at the cross section to see if it appears to be diseased. It would likely be discolored if it were diseased.
If so, itβs possible you can cut off the infested parts and still have a surviving plant. Be sure to disinfect your pruners between cutting diseased tissue and healthy parts in case it can be spread on your tools. You can use a diluted bleach solution or rubbing alcohol solution (one part to nine parts water).
Once you cut off the diseased parts, the first thing to do is see if your plant container can be replaced with one that drains so any excess water can be diverted from the root zone. If a disease has spread to the main stem, there might not be anything to do for your plant. Time will tell.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: The leaves/stalks in the center of my desert spoon plants are being eaten away about 6 inches up from the base.Β I donβt see any problem from the base and only water them about once per month with a hose. What is causing the problem and what can I do to make them healthy again?
A:Β It appears your desert spoons are a food source for a four-legged critter, probably javelina. These animals will feed on a variety of cacti and succulents. The solution is fencing or some sort of a detour around the plants you are trying to protect. Keep up the good care you are already providing and see if you can devise some fencing system that suits your landscape plan.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have six bougainvillea plants in my back yard. I have three on the east side and three on the west side planted about a year ago.Β Last summer the ones on the west side looked great and ones on the east side looked really bad. This summer the ones on the east side look great (see picture), the ones on the west side (not shown) look really bad.
We feed them and spray for bugs but still no luck. The water system goes off every other day at 7 a.m. and 3 p.m. My wife also waters them with the hose. But we canβt seem the get them to look good at the same time. Do you have any ideas as to what we can do?
A:Β Bougainvilleas are fairly tough plants once established and by the time they are a year old they should be doing well. The trouble last summer could have been from the shock of transplanting them. The plants on the east side appear to be getting western afternoon sun. That is where they do best and your plants on that side look great.
The plants on the west side appear to be getting eastern morning sun and might be shaded in the afternoon by the wall. Since full sun is prescribed for these plants, it could be a factor for the ones that may be shaded. Itβs hard for me to say from the photos (not shown) how much shade they get but itβs something to keep in mind.
From your description, the trouble this year may be due to overfertilizing and overwatering. Once or twice each year is all you need to fertilize and watering should be done less often and deeper than your current schedule. Try switching your irrigation schedule to once every seven to 10 days to a depth of 12 to 18 inches in the summer. Then you can reduce the irrigation to once every two weeks in the fall and every three weeks in the winter.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: We have infested-with-mealybugs prickly pears on a border with a neighbor who insists that the only way to control the infestation is to use a Bayer Tree and Shrub chemical.Β I so dislike and try to avoid these solutions. Can you direct me to an online intelligent discussion that isnβt sponsored by Bayer? Or do you have a nonpoisonous alternative?
A:Β I suspect what you are seeing isnβt mealybugs but rather Cochineal scale (Dactylopious coccus) on your prickly pear cactus. The easiest treatment is spraying them with a hose. You can also use a soap solution (1 tablespoon per gallon of water).
While the Bayer product will kill these insects, it is also likely to kill beneficial insects in the area that may be feeding on the scale insects. You and your neighbor shouldnβt expect to eradicate these insects. They are very common in our area and will likely continue to feed on the cactus no matter what method you choose.
Fortunately, they arenβt likely to kill these plants if you spray them with a hose periodically.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: What are these bugs on this milkweed?
A:Β The red and black ones are milkweed bugs. That might seem like a snarky answer but itβs the official common name for these insects otherwise known as Oncopeltus fasciatus. They can also be found on oleander plants, which might explain why the yellow insects are called oleander aphids (Aphis nerii).
Both species are commonly found on milkweed and oleander plants. Insects tend to favor specific plants or plant families when they feed. Milkweed and oleander are relatives from the same plant family and known for their sap that contains cardiac glycosides, which are poisonous. The insects that ingest it as a food source are able to sequester it and become protected to some extent.
If you watch other animals preying on these insects, you may notice they spit them back out. The red and yellow coloration is natureβs way of warning predators to leave them alone but not everyone understands the warning signs without a taste test.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q:Β When your time permits,Β Would you share your thoughts on this newest visitor to the garden? He/she has increased in numbers over the past weeks and I have yet to determine which plant is part of their meal choices.
A:Β The insect, Pyropyga nigricans, is a firefly species without a light. These are predatory insects and are garden helpers so youβre lucky to have them.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have a lilac bush, which I purchased from a mail order company. It is about 12 years old, and it has never bloomed a single flower.Β It grows larger each year and has lush green foliage. I have given it fertilizer but nothing seems to help. What am I doing wrong?
A: The common lilac (Syringa vulgaris) is a favorite in many places so I understand your desire to grow them. Unfortunately, your place might not be suitable. Lack of blooms is usually related to one of six causes: the age of the plant, temperature, alternate flowering, light, nutrition, or pruning practices. In your situation, I think the likely problem is temperature. Lilacs require a certain amount of cold to trigger blooming, also known as vernalization. We don’t usually get enough cold in Southern Arizona for this plant to bloom unless you live at higher elevations. There are lilacs at the Santa Rita Experimental Range near Green Valley than have been monitored for bloom times by the USA National Phenology Network for many years. The elevation there is approximately 3,714 feet above sea level. You can check their web site for details if you are interested: usanpn.org/nn/lilacs
In downtown Tucson, where the elevation is closer to 2,389 and winter is barely recognizable, itβs too warm.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: My husband pruned two of our Mexican bird of paradise shrubs way down. Only one came back and is doing nicely.Β We have watered and used Miracle Grow fertilizer on the other one but nothing happens. Will it come back next season or do we need to replant a new one?
A:Β If you arenβt seeing any new growth by now, I suspect itβs a goner. You can scratch the surface of the branches to see if there is any green beneath. The good news is you can probably plant new ones from the seeds of the one that is doing nicely. The Mexican bird of paradise (Caesalpinia mexicana) is one of three species that grow in our area. The other two are the yellow (Caesalpinia gilliesii) and red (Caesalpinia pulcherrima) birds of paradise. A good time to prune is once blooming is finished. If you cut them too short, you risk killing them. Try just cutting back the top third next time to be safe. The flower stalks on all three species may be removed to prevent seedpods from forming and to reduce the likelihood of volunteer seedlings.Β If the pods are left on the plant to dry and split, the seeds can be thrown a surprising distance.Β The red bird of paradise dies back to ground at temperatures below freezing. It generally regrows in spring,Β from the groundΒ and the dead parts can be pruned to a few inches above the ground in late winter. Mulching the baseΒ of plantΒ in colder areas may protect the plantβs crown until spring.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: I plan to buy a 15-gallon fruitless olive tree. Please tell me how much water daily or weekly it should be given once planted.Β The irrigation system in place for shrubs and trees comes on Monday and Friday for one hour. There are two black adjustable 10-gallon emitters where the tree will be planted. If the tree requires daily watering instead of the two days, I can water with a hose. When the temperature increases to 90 and higher, the irrigation system waters Monday, Wednesday, and Friday for two hours.
A:Β Olive trees should receive water every seven to 10 days in the summer to a depth of 24 to 36 inches. In the spring and fall, you can water every 10 to 14 days and in the winter, you can water every 14 to 21 days. Typically, two emitters can supply new trees as you described. As trees get older and their root zones increase in size, adding an emitter to the increasingly wider circle of drip irrigation would be appropriate every few years. The depth of irrigation can be measured with a soil probe. The schedule you are using now is watering too often and will encourage shallow root growth that will be more susceptible to our blast furnace summer heat.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
- By Peter L. Warren Special to the Arizona Daily Star
Q: These caterpillar bugs are all over my Texas mountain laurel (the same one that had the red and black plant bugs in March β which I sprayed off with a soap solution). There are probably at least 10 groups of these caterpillars on the tree. Suggestions?
A:Β These insects are called genista caterpillars (Uresiphita reversalis) and they are commonly found throughout the southwest on Texas mountain laurels. Their damage doesnβt affect the overall health of the tree unless there are unusually high numbers of them. The damage is often only cosmetic. The same soap solution can be used against these caterpillars. Soap acts an irritant and doesnβt always completely solve the problem. You might get the same result by spraying them with a hose. The benefit of the caterpillars is they are food for birds so you could leave them there and put up with the minor damage the caterpillars cause when feeding. Other solutions include pruning off the infested ends of branches, hand-picking the caterpillars, and various insecticides labeled for use on landscape trees and shrubs. An organic solution is spraying Bt (Bacillus thuringiensis) on the leaves where they are feeding. This works best when the caterpillars are young and most susceptible to the poison. The Bt bacteria are poisonous to caterpillars but not to anything else. Since there are several strains of Bt, make sure you use the one labeled for caterpillar pests. As always, when using any pesticide it is important to read the label and follow instructions to protect you and those other non-target organisms that might be exposed to the spray. By the way, the red and black bugs (Lopidea major) you saw earlier this year are also just a minor pest that feeds on Texas mountain laurel.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed totucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have a question about compost. My neighbors have two eucalyptus trees, which shed many leaves into my yard.Β Are these good to put into the compost or not? I have concerns because of oil they may have in the leaves.
A:Β Eucalyptus leaves are fine for compost. They need to be broken down like any plant matter put into compost so that any compounds that are otherwise harmful will be neutralized. The oil that you refer to has been reported to interfere with germination in some plants but that is not something to be concerned about with composted material.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: This may be an odd question but here goes: I have an apricot tree in my yard (at least 15 years old) and it was a dwarf/ semi-dwarf when I planted it.Β I chose one that required the lowest chilling hours. I cannot remember the type or the name. It is still a reliable producer, self-pollinating and ripens in May. Do you have any guesses what the name of it could be? I think I remember the name included the word Gold.
A:Β I suspect your apricot variety is Gold Kist. This is an excellent backyard apricot for warm winter climates. Its features include very good quality, freestone fruit, and it is heavy bearing. It is an early harvest variety, from late May to early June. It requires 300 chill hours and is self-fruitful.
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have a question related to the βDesert Museumβ palo verde.
I want to plant this tree at our house, but I am a little wary because of the threat of palo verde beetles getting to the roots and killing it prematurely. Perhaps you can help me assess this risk?
A:Β The main risk for these beetles is an unhealthy tree. The palo verde beetle is endemic to this area and there is little to be done to a tree that has been infested. They are known to attack stressed trees so the best prevention is to keep trees as healthy as possible. This is primarily accomplished by providing proper irrigation and pruning. Since these are native desert trees they can survive on rainwater but when we have drier conditions than usual, supplemental water can help. Typically for desert trees this means installing drip irrigation around the tree at the drip line and providing deep watering to a depth of 24 to 36 inches every 14 to 21 days in the spring, summer, and fall. In the winter you can skip the irrigation, assuming we have normal winter rains. Proper pruning when the tree is young will result in a mature tree that is structurally stronger, lives longer, and is less costly to maintain. Donβt be in a hurry to prune at planting. A newly planted young tree should be given a chance to put down roots before taking any branches off unless they were damaged in the planting process. After a year or so it will be time to structurally prune your tree to ensure its long-term health.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: This year, we have some peaches with dimples. The fruit is rotten inside. Could it be a plant pathogen of some kind?
A:Β The short answer is yes. Your peaches are likely suffering from a pathogen as a result of insect feeding damage. The prime suspect in this case is the leaf-footed bug. These insects have piercing-sucking mouthparts and while feeding on young developing fruit leave scars that are known as cat-facing and sometimes this feeding activity will introduce fungi that may cause the rot.
Leaf-footed bugs are common in our area and may feed on a variety of plants including pomegranate, pecan, citrus, and peaches. They are difficult to manage once in the adult stage because they can fly and move about quickly.
There are insecticides available, but they are only effective on the young bugs. These insecticides are harmful to bees, so take care to avoid spraying plants in bloom. Monitoring for and removing egg masses in the early spring is another tactic that is potentially more successful if you are persistently looking in the spring when eggs are laid and young bugs are emerging from them.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: What is going on with my rosemary bush? Two days ago I looked at the bush and discovered damage.
A:Β Rosemary (Rosmarinus officinalis) is a shrub that grows well in the desert. The natural form is shaggier than the sheared version you have growing. The damage you are seeing is likely a result of regular shearing of the foliage. Often shearing creates a shell of green that prevents light from entering the inner parts of the plant. Eventually dead spots will occur and regrowth from those branches will not likely happen. A better treatment would be less frequent light pruning as necessary and in a more selective fashion to allow the plant to achieve its natural form and to open up the plant a bit to light, air, and water.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: We have 30-year-old Rhaphiolepis indica planted in a slightly raised planter.Β One side was particularly hit hard by the freeze a few years ago (17 degrees in Tucson in February), or so we thought, until we caught a couple of deer munching on that particular shrub. It never recovered from the munching. The shrubs on the other side of the planter were doing well until four deer became emboldened and began munching on the flowers and new leaf growth on the other side near our front gate. Those plants, too, have stopped putting on new leaves and weeks later look exactly like the deer left them. What can we do to rejuvenate the plants/encourage them to grow again?
A:Β Deer munching is definitely a hazard for Rhaphiolepis indica (Indian hawthorn), so some sort of fencing or detours around your shrub are required before you spend a lot of time on rejuvenation.
The best time to prune is around May or when it is finished blooming. You can selectively prune out the damaged branches where deer were feeding. From your photo the shrub looks pretty full and selective pruning should help open it up to more light, air, and water as well. Otherwise, continue to provide sufficient water, fertilize annually and monitor deer activity as needed.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.comΒ
- By Peter L. Warren Special to the Arizona Daily Star
Q: I am sending two photos of my desert willow tree, now in its fourth spring. The buds form, grow and then dry out before opening.Β Have taken samples to Mesquite Valley Growers. They see no evidence of pests or disease, and recommended more water and fertilizer. The leaves seem smaller and shorter than others I see.
A:Β I agree with Mesquite Valley Growers; the symptoms you describe are likely related to insufficient watering. The recommended schedule for desert trees is once every two to three weeks in the spring, summer, and fall to a depth of 24 to 36 inches. An annual spring fertilizer application wouldnβt hurt either, making sure the fertilizer is watered in to reach the absorbing roots.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I purchased this sugar bush at Desert Survivors Native Plant Nursery two years ago. It chronically looks like it isnβt getting enough water; there are dry, brown leaves. It is planted in desert soil with a cactus mix amendment. It is on a shrub line that runs twice a week right now, for 2Β½Β hours. I have played with the emitter flow and am putting about 20 gallons each application. It gets sun until about 3 p.m. Is there anything I can do to help it thrive?
A:Β Sugar bush (Rhus ovata) is a moderate water user but twice per week at 20 gallons each application seems like a lot of water for a native shrub. If you arenβt checking to see how deep the water is going, I suggest using a soil probe to determine the depth of the watering. Ideally, water should reach a depth of 24 to 36 inches. I recommend backing off your irrigation to once a week for the summer and once every two weeks in the spring and fall.
Overwatering sometimes shows similar symptoms to underwatering, so looks can be deceiving.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed toΒ tucsongardensage@gmail.com
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