Garden Sage - Tough yellow bells; snapdragon rust; a plant from Australia
- Updated
Answers to your gardening questions from an expert in Southern Arizona.
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have an area about 15 feet by 12 feet that is bordered on two sides by sidewalk on the south side of my house. I have an 8-year-old thornless mesquite tree planted in this area. I am worried about the possibility of the roots damaging the sidewalks. Should I remove this tree? If I do, what type of tree would you recommend for that size area that would not harm the sidewalks? This area is next to my front patio and I would like to have some shade for it.
A: Thornless mesquite trees are a South American hybrid also known as the Chilean mesquite. The mature size of this tree is approximately 30 feet by 30 feet and that is only the above-ground size. The roots may spread twice as far, so your sidewalk is in jeopardy.
Small trees that could fit this space include kidneywood, Texas mountain laurel, Arizona rosewood, little leaf ash, and leather-leaf acacia. These may not give the shade you desire.
A few slightly larger trees that might fit are Texas ebony, palo blanco, and cascalote. I am sure there are others, so it would be good to visit our local nurseries to see what they have available.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: Some of my snapdragons are covered with dark spots and it seems to be spreading to neighboring plants. What can I do to stop this problem?
A: From examining your plant sample, the problem is a disease called snapdragon rust that is caused by the fungus Puccinia antirrhini. This is a widespread pathogen that has been around since the 1800s. Small, yellow spots on the leaves are the first indication. Unless you are paying close attention, you won’t notice the yellow spots until they mature into chocolate-brown pustules. The spores that emerge from these pustules are spread by wind mostly but also possibly by rain and insects. The infection and incubation of these spores occurs best when temperatures are between 50 and 75 degrees, and that is what we have been experiencing in recent weeks.
Once temperatures exceed 90 degrees or so, the spores cannot survive. Infested plants can be removed and destroyed to reduce the immediate source of spores. There are also fungicides available to manage the rust if removing the plants isn’t in the plan. Look for products labeled for managing rust on landscape plants. Rust-resistant varieties of snapdragons are available. Planting them with space between to allow for air circulation is helpful, as is making sure to use drip irrigation rather than overhead sprinklers.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have three of these in my yard, plus three that came up recently in disturbed ground. What is it?
A: Your plants are called Senna phyllodinea, or desert Senna or silver leaf cassia. It is native to Australia and does well here. It can propagate by seed. The slender silver leaves are a good desert adaptation for reflecting the sun and reducing exposure to it. They can grow into a large shrub of 6 feet by 6 feet if allowed. The fragrant yellow flowers in February are a welcome sight for many.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I live in Tucson. Alkaline soil, lots of sun, not much rain. I have found contradictory info on fertilizing Tecomas. Local websites either say “responds well to regular fertilizer,” “fertilize with ammonium sulfate” or “this plant particularly hates (fertilizer).” Does anyone have a decisive answer from a reliable source?
A: Tecoma stans, aka yellow bells, has a reputation as a tough plant that needs little help once established, except for occasional pruning and pest management. Although I couldn’t find any research detailing its exact needs, all plants need water and nutrients.
If you want to have your soil tested by a laboratory, many of them will make fertilizer recommendations based on the results and which plants you are planning to grow. If you would rather experiment without a soil test, I recommend a slow release tree and shrub fertilizer in the spring and also recommend regularly scheduled drip irrigation every two or three weeks unless it is raining.
You can use composted manure or another organic material that has been composted as a slow-release fertilizer. In the end, your plants will help you figure out their needs by how well they appear and grow. For example, plants that begin to have yellow leaves with green veins are often showing a sign of nutrient deficiency. Taking a look at your landscape plants once a week or so to see if problems are occurring is one of the cornerstones of integrated pest management and a great way to catch problems before they get out of hand.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have had two mountain laurel bushes for 15 years . Suddenly last fall, one dropped its leaves. The stems were green and it is starting to bloom and add some new leaves. The other bush had some white places, not sure if there was an aphid attack, I did not notice a lot of this white on the bad plant.
A: Texas mountain laurel (Calia secundiflora) are fairly tough plants and have only a few minor insect problems that may cause limited defoliation or distortion from feeding.
Losing all the leaves as you describe is likely some sort of environmental stress. Consider what irrigation your plants receive since that is a limiting factor for most plants. Dropping leaves and blossoms is a normal reaction to lack of water. Leaves are where water vapor leaves a plant so to reduce the amount of water escaping; the plant may drop its leaves. It’s good to see the leaves are growing back. It’s possible the plant will grow much better with all the rain we’ve had along with continued irrigation through the warmer months.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have been collecting compost material in my kitchen then burying it directly in my garden for several years. I didn’t plant a garden this year but still bury fruits and vegetables. This year I discovered what I think are grubs. How can I get rid of them?
A: The grubs are in your soil because you made it so nice for them. These beetles do best in soil rich in organic matter because they feed on it and so the adult beetles will lay eggs where they find good soil or directly into compost piles. You can get rid of them if your garden is small and you don’t mind sifting through the dirt.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I had some lower branches trimmed from my ponderosa pine in December. How long will it take for the sap to quit flowing?
A: Sap flowing from a tree wound is part of its defense system . The sap flow will continue until the vessels clog and the tree seals the wound. There is no need for anything to be applied. Applying something to the wound is not good for the tree. It used to be a common practice to paint pruning wounds but it turns out trees do a better job of sealing their own wounds and the paint sometimes hinders that process.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: My primary question is regarding planting a grass that would be tolerant to the “colder” weather that would not require a re-seeding of rye grass. Would it not be possible to make sure the bermudagrass would stay half way green through the dormant season? Or a different type of grass that would not have to be re-seeded with the rye grass. Also, is it really necessary to water two times a day on the rye seeding at this time?
A: The best grass for this part of the world continues to be bermudagrass. It can deal with high sunlight, high air temperatures, salty water/soil, shallow soil and heavy use. Unfortunately, the life cycle of bermudagrass includes going dormant. Think of dormancy as sleep and how it is hard to go without any for very long and remain in good health. Overseeding is optional but it helps keep some green if that is your goal. It also helps keep your lawn thick, which helps shade out weeds. Watering twice per day is recommended for germination. Once it starts growing you can water every other day and then once a week once the temperatures cool down for the winter.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have a clean yard, in which I have a few plants and trees, and had a large Mexican primrose that came up by itself. Last week gophers, plural, got the primrose and it disappeared. How did they find it? The ground for more than 40 feet around the primrose is bare and had no gopher mounds of dirt. Nothing, yet the tunnel surfaced an inch from the plant and they proceeded to eat it. I set a trap and killed one gopher overnight, but the next day there was an additional mound and the plant had disappeared. Do they come above ground to scout around at night? I’m mystified.
A: Gophers are nocturnal so it makes sense that you could catch them overnight and lose plants to them at the same time. Their crescent-shaped mounds, tunnels, and plant damage are certainly signs they are present. Many animals find plants by smell and they may have been scouting above ground at night before building that part of the tunnel. While they feed on the roots primarily, they will also take whole plants underground. Continue trapping and try to exclude them from desired plants with hardware cloth buried beneath the beds.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: Can you help identify a shrub about 4 to 5 feet high, wide with fuzzy leaves, and a white umbrella flower? This photo shows what appears to be the seedpod.
A: It looks like Mexican olive (Cordia boissieri) and confirmed by our friends at the University of Arizona Herbarium. It’s native to southern Texas and can be found in the wild. It isn’t related to actual olives but it produces a similar looking fruit that isn’t palatable to humans but wildlife like them. The flowers are nice though so it makes a suitable landscape shrub/small tree if you have room for something that can grow to 30 feet given the proper accommodations. However, it doesn’t tolerate freezing temperatures.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: How do I keep cockroaches from invading my house from outside?
A: There are many species of cockroaches and only a few of them like to live with humans. For some species, entering your home is an accident and they can be dispatched with a broom. They are nocturnal and attracted to lights, water, food, and shelter. To protect your home, make sure it’s difficult for them to get inside by sealing any holes in the foundation, making sure door sweeps are in good condition, or traps can be used.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: My yard has a palo verde borer beetle infestation. I have personally smashed/stepped on/killed this many the last three years: 2014 – 54, 2015 — 53 (June 18-July 21), 2016 — 66 (June 19-July 31). I documented how many per night. And documented male/female numbers.Front yard has a 12-year-old Desert Museum palo verde with the most infestation. It lost a quarter of its branches this fall. Backyard has a 30-plus-year-old ash tree. In 2016, 28 of the 66 were from the ash. I tried two applications of beneficial nematodes (September 2015 and April 2016) with no reduction. Any help and suggestions are welcomed.
A: Palo verde beetles are typically an indicator of a stressed tree. They are often found when dead palo verde trees are removed but they are rarely responsible for the death of trees. Trees often die of multiple causes including the many environmental factors they are exposed to in our landscapes. It is usually these stresses and other factors unrelated to the beetles that cause tree death, even when the beetle larvae are present feeding on the roots. My suggestion is to make sure you are doing everything you can to care for your trees. This will go a long way toward protecting them from an early death. Beneficial nematodes are a wonderful thing in the right circumstances but there is no research I am aware of that shows they have any affect on palo verde beetle populations.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: Please — when you tell someone to water a tree down about 4 feet — will you please use other parameters? How am I supposed to know when something is wet down to 4 feet? Dig a hole? I didn’t read it today, and I can’t say that you are responsible for this — but many times past over the years I have had the same reaction. It’s just that today I am finally taking the time to write and your email address is handy!
A: Watering depth can be measured in several ways including some fairly sophisticated devices, calculating the output from your drip irrigation emitters, and by using a soil probe. The soil probe is the least complex and the least expensive. This device can be as simple as a piece of rebar with a handle and a pointed end. These probes are sold in a variety of garden shops and even our Cooperative Extension office sells them to benefit the Master Gardener Program. Some are as cheap as $5 and others are a bit more expensive. By pushing the probe into the soil after irrigating you can tell approximately how deep your water is going. The dry soil will provide more resistance than wet soil so you can stop pushing when it becomes more difficult and measure how much of your probe is in the soil. It’s not as much fun as math but it can help you adjust your irrigation practices.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: We purchased our home in Tucson Estates a few years ago. As part of the landscaping, there are bougainvillea plants along a fencerow. Every summer we have battled some kind of an insect that eats the green leaves. When we begin to have the cooler temps, the insects seem to be fewer and the plants finally begin to blossom a lovely red. With our recent warm temperatures, the insects are back in abundance. I’d really like to get on top of this before next spring so that we can have healthy plants and blossoms. Is there any hope? If so, what can we do?
A: There are two known caterpillar pests of bougainvillea. Disclisioprocta stellate, aka the bougainvillea looper and the somber carpet moth, is a moth originally from Africa that is now found commonly in Hawaii and the southern United States. The adult is a small brown moth and the caterpillar is also brown and small. Loopers crawl by arching their body into a loop shape so they are easy to identify while moving. Asciodes gordialis, aka the bougainvillea caterpillar moth, is also a small brown or tan moth found in the southern states. The caterpillar is green and doesn’t loop while crawling. Both of these insects will disappear in the cool part of the year and resume activity in the warm times. Identifying them would be useful and probably fun for me so I would like to know when they begin feeding again in the spring if you don’t mind. To manage them, you will use the same strategy. You can look for caterpillars now and whenever you start to see new damage and pick them off the leaves. They are helpless off the plants. You can also spray the leaves with Bacillus thuringiensis (Bt) labeled for caterpillar pests to kill the ones you overlooked. Looking more often when you notice new damage will help. There will be periods of time when they are less active when a quick weekly examination will suffice. The insect in the photo you sent is a green lacewing and is a beneficial insect that might help with your pest management. For this reason, the Bt is a good choice because it will harm only caterpillars.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren, Special to the Arizona Daily Star
- Updated
Q: I have a question about our magnolia trees. It appears that one is dying and I am wondering if that is because the grass below them was removed. When the grass was there, the trees were very lush. Since the grass was removed and the ground covered with rock (and no water), it has changed the life of the magnolias.
A: I think you answered your own question. The tree was possibly receiving significant water from the grass irrigation. The fix for that would be to set up an irrigation system for the trees. A drip system arranged in a circular fashion around the drip line of the tree would be ideal. Non-native trees like the magnolia should be receiving 24 to 36 inches of water every two to three weeks in the winter. In the spring and fall, increase the frequency to 10 to 21 days and in the summer every seven to 14 days.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren, Special to the Arizona Daily Star
- Updated
Q: Please advise if we can plant our hopseed bushes; foothills palo verde or desert museum palo verde; and “Leslie Roy” hybrid mesquites now. We’re concerned the weather might still be too cold. We’re thinking it might be better to wait for a few weeks, say third week of February. We live in Academy Village at Rincon Valley, southeast of Tucson, at an elevation of about 3,000 feet.
A: The cool part of the year is ideal for planting woody plants. They are dormant to some extent and less likely to experience transplant shock if the weather is cooler. The more time you allow the plant to become established in its new location before the summer heat begins, the better chance the plant will have to survive. Don’t put any fertilizer on them because you don’t want to stimulate new growth now. Also don’t prune them because it adds additional stress to the situation. If you need more information, the Arizona Community Tree Council has a nice and short tree-planting guide on their website.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren, Special to the Arizona Daily Star
- Updated
Q: Several years ago I had a new evaporative cooler put on my roof — one that purges every few hours. The workman asked where I wanted the water to drain. I thought it would be great to use the water on some non-irrigated bushes below the roof. The man didn’t warn me that the water would be salty, and in time it would kill the bushes, which happened within a year. It’s been about four years since I’ve redirected the flow. Now I would like to plant gardenias in that area. I know they are sensitive to salt. I’m wondering if the rainwater draining off the roof has washed away the salt? I’ve imagined digging deep holes, throwing out the dirt and putting in garden soil. What do you think I should do? How deep and wide should I dig these holes? Would adding acid neutralize the salts?
A: If gardenias could choose their location, they would seek acid, moist, well-drained, high-organic-matter soils in a sunny but not too hot spot. Not exactly what we see commonly in Southern Arizona. That’s not saying you can’t grow them here but you will need to choose a good spot and maintain their surroundings to keep them alive and healthy. It’s best to have your soil tested if you are planning to plant non-natives to make sure they won’t be compromised from the start. My guess is the spot you chose is still salty unless you have been adding organic matter and giving it a good soak once a month to wash the salt through.The rainwater draining off the roof probably left salt in the soil when it evaporated. It’s hard to swap out your soil or change the characteristics of soil for more than a short time. Salinity, high pH and the lack of organic matter will be a going concern. If you are determined to grow these plants, the easiest way is to plant them in containers or raised beds with good soil. Since irrigation water is salty and so is fertilizer, you will still have to give the plants a good soak periodically to wash the salt through the soil. Keep an eye out for yellow leaves with green veins, which is a sign of nutrient deficiency. Also make sure to give them only northern or eastern exposure so they don’t bake in the desert sun.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren, Special to the Arizona Daily Star
- Updated
Q: My yard is covered in “Horrible Evil Spiky Seeds of Death,” as we call them, though I’m sure that’s not the technical name. I think they come from the pictured tree. Humans can’t go outside without spending several minutes prying the damn things off their shoes. Dogs literally weep doggie tears to walk out there. Is this tree some kind of precious native specimen or can I burn it to the ground (metaphorically) without the stain of eco sin on my soul?
A: Your Horrible Evil Spiky Seeds of Death are also known as Tribulus terrestris, goat head, puncture vine and other words unsuitable for a family newspaper. They didn’t come from a tree but from a small green plant that grows prostrate to the ground. It’s a summer annual so all you see now are the seeds. Once they germinate and begin to grow, you will notice the green foliage and eventually the nice yellow flowers from whence the seeds develop. To step on a seed is very painful, as your dog would say if dogs spoke English. They are able to puncture some bicycle tires and so they are not well-liked by humans either. I switched to thicker tubes to reduce the number of flat tires. You can keep the tree and still wage war on the guilty plants by pulling them out of the ground as soon as you see them so they won’t produce more seed. Some people prefer to use an herbicide and any broadleaf variety will do. Please follow the label instructions for any pesticides you use to prevent injury to any non-target organisms.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: Recently we purchased pansies at Wal-Mart. They immediately wilted. I know they like to be in bright sun and so I placed them in an environment similar to what they were at Wal-Mart. Any suggestions to thrive? I’ve watered them when the soil is dry to touch and haven’t replanted them. Would like to think I have a green thumb. Probably not.
A: Pansies and violets (Viola species) are great for adding color to your landscape in the winter and spring. In general, they can be planted in sun (as long as it’s not too hot) or partial shade although some species prefer variations on this rule of thumb. If you look at a climate zone map, you might notice that it appears to be too hot for them in the Tucson area in the summer. They will look bad once the weather warms to their limit so we can treat them like annuals and replace them with something else. They also need water twice a day for the first couple weeks when they are getting established. This may be why yours wilted.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have researched and talked to many people about how to kill Bermuda grass most effectively while being as environmentally friendly as you can be. I have heard of several different methods, including covering the whole area in plastic as well as using Roundup as possible methods. I would like your opinion on the best method to use to kill Bermuda grass. My understanding is the only chemical way to do it would be with Roundup, but my wife is very against that idea. I have read the research on the biochemical makeup of Roundup and I am not sure if it is truly toxic if you only use that one to two times.
A: Roundup or any other product containing the active ingredient glyphosate is the most effective and least labor-intensive way to manage/kill Bermuda grass and many other weeds. It does require repeat applications and the grass needs to be green when you spray to be most effective. Other methods include scraping off the top layer of grass and covering it with landscape fabric, clear plastic, or cardboard, and digging the grass up with a shovel. You can certainly kill much of the grass through solarization, starvation, or digging it up. The problem, as you may know, is the roots, or parts of them, are still alive in the soil in many cases with all of these methods. They will eventually find a way around or through the covers so it may be more labor intensive to manage it. Bermuda grass spreads by underground stems (rhizomes) and aboveground runners (stolons), not to mention seed. A systemic herbicide can get to the root of the problem with less effort. No matter which method you choose, if you live in an area with unmanaged Bermuda grass nearby, it will eventually return so you need to remain vigilant in your management. Regarding the toxicity, according to the Monsanto label, glyphosate is a moderate irritant if eyes and skin are exposed but is practically nontoxic otherwise unless you are an aquatic organism. As always, it is best to follow the instructions on the label of any pesticide to avoid harming any non-target organisms.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I read your article about Bermuda grass and have a question concerning the condo development where we live. The complex includes a large area of grass and mesquite trees. The HOA overseeds in the winter. This makes for a beautiful green area and also greatly cuts down on blowing dust. The landscaping company has advised the HOA to not overseed every three years to help the Bermuda grass. Does this make sense to you? I see many places (e.g. golf courses) that overseed every year and the Bermuda grass appears to come in just fine.
A: Yes, it makes sense. Continuous overseeding can cause stress to Bermuda grass if proper care is not taken for proper overseeding timing/preparation and proper spring transition back to healthy Bermuda grass conditions. Rye grass is a common cool season grass used to overseed Bermuda grass in the fall. Extended rye grass seasons on the front end from early overseeding and well beyond spring transition into summer will weaken the root system and reproductive capabilities of Bermuda grass. If these unhealthy practices are repeated annually, exhausted and stressed Bermuda grass diminishes over time and requires renovation. Thus, skipping overseeding every few years can provide the Bermuda grass a nice long growing season from March to November to rebuild roots. If the stress is minimized by best management practices and a good 100 days of optimal growing conditions are provided each year, Bermuda grass can be overseeded regularly. The minimum 100 days should be in the June through September timeframe. For more details on the timing and preparation, there is a nice publication available online by the University of Arizona turf grass specialists, David Kopec and Kai Umeda.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have a mature grapefruit tree I have been maintaining for three years ago. I keep it watered, fertilized and trimmed. It has always given me many wonderful juicy pink grapefruit, which I love, and share with friends. This spring, I noticed very few blossoms and now there are very few (probably less than 50 total) grapefruit on the tree. The existing fruit has extremely thick rinds, about 1ƒ inches thick, leaving very little room for the inside fruit. Did I do something wrong to have this problem? I love this tree and the fruit and would appreciate any help you can give me to do whatever it takes to bring back the bounty come next spring.
A: I recommend you double-check the fertilizer amount, timing, and type you are supplying. Over time, trees with an imbalance of nutrients may develop thick rinds. Nitrogen is often the main ingredient in fertilizer but trees also need a small amount of phosphorus and potassium. There are some fertilizers designed and sold for citrus. If you aren’t already using one of these, it might be worth switching. You also might also double-check the watering schedule to make sure that is correct. It should be every 14 to 21 days to a depth of 36 inches in the winter, every 10 to 14 days in the spring and fall, and every seven to 10 days in the summer. Trimming your citrus tree is not something recommended unless there are dead or damaged branches.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have a Mexican palm that is about 25 feet high and still growing. Is there any way to slow it down or stop it from growing? Also it is 6 feet from an in-ground pool and 2 feet from brick wall. Should I be concerned about this?
A: Palm trees, like other tree species, tend to slow down growth when they receive less water. You can’t stop it from growing unless you use a chainsaw. Trees growing too close to structures can be a problem as their roots grow and seek water. I think your description warrants a visit from a certified arborist to determine the gravity of your situation. Palm trees are not as big a problem as some other trees that have larger root systems but they can still disrupt hard structures over time.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I think it’s nearly time to begin pruning my grapevines (two Red Flame and one Thompson green) and seems like it’s a good idea to address last year’s pests. Although the photo shows the arbor in shade, the vines get six to eight hours of sun daily. In the summer, the drip system provides each vine with one gallon per hour, four days a week, for an hour and a half. And last summer, boy did we have bugs. I use Bt for one kind of caterpillar that has been with us since the beginning, coming up on four years, but it didn’t seem to faze them. I’d prefer a systemic, because our monsoons wash sprays off. I’m happy to forgo harvesting grapes for another year or two. What is your recommendation?
A: Bt (Bacillus thuringiensis) is helpful in managing caterpillars such as the grape leaf skeletonizer (Harrisina brillians). Bt doesn’t have any affect on the various species of leafhoppers that are causing the damage in the photo. Leafhoppers suck the sap from leaf cells causing the yellow appearance you are seeing. Grape plants can withstand a good amount of feeding damage before fruit yield is affected so you might not have to do anything. There are also natural enemies that feed on the leafhoppers so you probably already have some help managing them. If you want to determine if treatment is recommended, you can monitor the population by counting the number of leafhoppers per leaf on a random sample of leaves. If the number per leaf exceeds 15, then it might be worth treating. There are systemic insecticides available for this purpose and they can be applied as a soil drench. Active ingredients for these chemicals are toxic to bees and other animals so please follow label instructions if you go this route. So my recommendation is to assess the situation before treating because you might save money by monitoring them this spring.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: We live on a property in the near foothills on the east side of town that has a number of saguaros. There is one cactus that we’d always assumed was just an odd looking saguaro because it is about the same size as many of the saguaros in our yard. This morning, we noticed that it has two blooms and they are quite different from those on saguaros. We also realized that while the spines are similar to those on a saguaro, they differ too. Can you help us identify this cactus?
A: From your photo this appears to be an Argentine saguaro (Echinopsis terscheckii), aka cordon grande. This species is sometimes planted in our area for its ability to withstand cold weather. It grows faster than the native saguaro and is hardier so it can be grown in slightly colder climates. As you noticed, the flowers look more like a cereus than a saguaro and the spines are longer as well.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: This fall I found I had holes in my tomatoes. I cut some open and there were some kind of brown hard stuff in the fruit. Any idea what they are?
A: The signs indicate tomato fruitworm (Helicoverpa zea) damage. These insects are fairly common and also known as corn earworms and cotton bollworms, depending on the crop where they are found. The eggs are laid on the plant and the larvae bore into the fruit where they can stay until they complete their development and drop to the soil to pupate. The brown stuff is probably frass (caterpillar poop). These insects are difficult to manage once inside the fruit so it is best to catch them before they enter and/or dispose of infested fruit before they have a chance to emerge. Lima beans can be used as a trap crop because they prefer them to tomatoes. There are also pheromone traps available to monitor when the adults are flying so you can tell when to start looking.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: You recently provided some info on fertilizing citrus and I have located the chart you referenced. You often recommend watering to a depth of 36 inches, so I’ve been using a deep watering rod on my three mature fruit trees (10-12 feet, grapefruit, lemon, and orange). What is the preferred method for applying fertilizer? Should I use a pre-mixer with the watering rod below grade or apply the fertilizer on the surrounding ground under the tree and soak it from the top down?
A: The preferred method of fertilization is to spread it around the drip line of the tree and water it into the soil as you described. This is also the preferred method for irrigation so you can do both at the same time. I don’t recommend the deep watering rod because it likely bypasses some or many of the absorbing roots of the tree, which are typically in the top 1 to 2 feet of soil.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: We have two Texas Ranger bushes that are each about 5 feet tall. We were at a local nursery recently to get some information about trimming our trees and the subject of cutting back the bushes came up. The person at the nursery suggested cutting the bushes down this February to only 1 foot high, straight across (almost like a flat-top haircut). That seemed pretty drastic to me and I wanted to get your opinion.
A: What your nursery person described is called renovation pruning and it is appropriate for some situations such as when shrubs become too large and you want to improve their aesthetic value. It is a drastic method and shouldn’t be pruned this way every year because it is stressful for the plant. It also works best if you are able and willing to follow up the buzz cut with some selective pruning a few months later. The initial severe cutting of all branches to 12-18 inches above ground will cause a flush of growth in the spring and into the summer. Once this happens it is best to follow up with the selective removal of about 50 percent of the branches at the base to thin out the canopy. Then prune the tops of the remaining branches to different heights, making sure to prune just above outward facing buds to encourage healthy branching to the outside of the plant. If this still seems too drastic or you aren’t interested in cutting your shrubs down to size, you could simply do the selective pruning part without cutting all branches back to the 1-foot level.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
- Updated
Q: I have two Meyer Lemon trees, bought and planted at the same time. One is in the back yard where it gets lots of sun. The other, in the side yard, only gets partial midday sun. The leaves on the side-yard tree are yellow and the tree bears little fruit while the other, although shaded by a large evergreen tree, has flourished and looks healthy except for a back branch which is turning yellow. Can you offer any suggestions as to the cause of this situation?
A: I think you may have answered your own question, assuming your trees are otherwise healthy and receiving proper water and nutrients. Citrus trees need full sun to be at their best. From your description, the healthier tree is getting “lots” and the side yard only gets partial sun. The ideal would be eight hours of sun and that is not possible with only midday sun. Since “lots” is not a number, I will guess that even the tree in the backyard could do better if your large evergreen tree didn’t shade it. If it’s not possible to change the surroundings to allow more sun on the trees, you might consider moving them to a sunnier spot.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have an area about 15 feet by 12 feet that is bordered on two sides by sidewalk on the south side of my house. I have an 8-year-old thornless mesquite tree planted in this area. I am worried about the possibility of the roots damaging the sidewalks. Should I remove this tree? If I do, what type of tree would you recommend for that size area that would not harm the sidewalks? This area is next to my front patio and I would like to have some shade for it.
A: Thornless mesquite trees are a South American hybrid also known as the Chilean mesquite. The mature size of this tree is approximately 30 feet by 30 feet and that is only the above-ground size. The roots may spread twice as far, so your sidewalk is in jeopardy.
Small trees that could fit this space include kidneywood, Texas mountain laurel, Arizona rosewood, little leaf ash, and leather-leaf acacia. These may not give the shade you desire.
A few slightly larger trees that might fit are Texas ebony, palo blanco, and cascalote. I am sure there are others, so it would be good to visit our local nurseries to see what they have available.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: Some of my snapdragons are covered with dark spots and it seems to be spreading to neighboring plants. What can I do to stop this problem?
A: From examining your plant sample, the problem is a disease called snapdragon rust that is caused by the fungus Puccinia antirrhini. This is a widespread pathogen that has been around since the 1800s. Small, yellow spots on the leaves are the first indication. Unless you are paying close attention, you won’t notice the yellow spots until they mature into chocolate-brown pustules. The spores that emerge from these pustules are spread by wind mostly but also possibly by rain and insects. The infection and incubation of these spores occurs best when temperatures are between 50 and 75 degrees, and that is what we have been experiencing in recent weeks.
Once temperatures exceed 90 degrees or so, the spores cannot survive. Infested plants can be removed and destroyed to reduce the immediate source of spores. There are also fungicides available to manage the rust if removing the plants isn’t in the plan. Look for products labeled for managing rust on landscape plants. Rust-resistant varieties of snapdragons are available. Planting them with space between to allow for air circulation is helpful, as is making sure to use drip irrigation rather than overhead sprinklers.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have three of these in my yard, plus three that came up recently in disturbed ground. What is it?
A: Your plants are called Senna phyllodinea, or desert Senna or silver leaf cassia. It is native to Australia and does well here. It can propagate by seed. The slender silver leaves are a good desert adaptation for reflecting the sun and reducing exposure to it. They can grow into a large shrub of 6 feet by 6 feet if allowed. The fragrant yellow flowers in February are a welcome sight for many.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I live in Tucson. Alkaline soil, lots of sun, not much rain. I have found contradictory info on fertilizing Tecomas. Local websites either say “responds well to regular fertilizer,” “fertilize with ammonium sulfate” or “this plant particularly hates (fertilizer).” Does anyone have a decisive answer from a reliable source?
A: Tecoma stans, aka yellow bells, has a reputation as a tough plant that needs little help once established, except for occasional pruning and pest management. Although I couldn’t find any research detailing its exact needs, all plants need water and nutrients.
If you want to have your soil tested by a laboratory, many of them will make fertilizer recommendations based on the results and which plants you are planning to grow. If you would rather experiment without a soil test, I recommend a slow release tree and shrub fertilizer in the spring and also recommend regularly scheduled drip irrigation every two or three weeks unless it is raining.
You can use composted manure or another organic material that has been composted as a slow-release fertilizer. In the end, your plants will help you figure out their needs by how well they appear and grow. For example, plants that begin to have yellow leaves with green veins are often showing a sign of nutrient deficiency. Taking a look at your landscape plants once a week or so to see if problems are occurring is one of the cornerstones of integrated pest management and a great way to catch problems before they get out of hand.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have had two mountain laurel bushes for 15 years . Suddenly last fall, one dropped its leaves. The stems were green and it is starting to bloom and add some new leaves. The other bush had some white places, not sure if there was an aphid attack, I did not notice a lot of this white on the bad plant.
A: Texas mountain laurel (Calia secundiflora) are fairly tough plants and have only a few minor insect problems that may cause limited defoliation or distortion from feeding.
Losing all the leaves as you describe is likely some sort of environmental stress. Consider what irrigation your plants receive since that is a limiting factor for most plants. Dropping leaves and blossoms is a normal reaction to lack of water. Leaves are where water vapor leaves a plant so to reduce the amount of water escaping; the plant may drop its leaves. It’s good to see the leaves are growing back. It’s possible the plant will grow much better with all the rain we’ve had along with continued irrigation through the warmer months.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have been collecting compost material in my kitchen then burying it directly in my garden for several years. I didn’t plant a garden this year but still bury fruits and vegetables. This year I discovered what I think are grubs. How can I get rid of them?
A: The grubs are in your soil because you made it so nice for them. These beetles do best in soil rich in organic matter because they feed on it and so the adult beetles will lay eggs where they find good soil or directly into compost piles. You can get rid of them if your garden is small and you don’t mind sifting through the dirt.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I had some lower branches trimmed from my ponderosa pine in December. How long will it take for the sap to quit flowing?
A: Sap flowing from a tree wound is part of its defense system . The sap flow will continue until the vessels clog and the tree seals the wound. There is no need for anything to be applied. Applying something to the wound is not good for the tree. It used to be a common practice to paint pruning wounds but it turns out trees do a better job of sealing their own wounds and the paint sometimes hinders that process.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: My primary question is regarding planting a grass that would be tolerant to the “colder” weather that would not require a re-seeding of rye grass. Would it not be possible to make sure the bermudagrass would stay half way green through the dormant season? Or a different type of grass that would not have to be re-seeded with the rye grass. Also, is it really necessary to water two times a day on the rye seeding at this time?
A: The best grass for this part of the world continues to be bermudagrass. It can deal with high sunlight, high air temperatures, salty water/soil, shallow soil and heavy use. Unfortunately, the life cycle of bermudagrass includes going dormant. Think of dormancy as sleep and how it is hard to go without any for very long and remain in good health. Overseeding is optional but it helps keep some green if that is your goal. It also helps keep your lawn thick, which helps shade out weeds. Watering twice per day is recommended for germination. Once it starts growing you can water every other day and then once a week once the temperatures cool down for the winter.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have a clean yard, in which I have a few plants and trees, and had a large Mexican primrose that came up by itself. Last week gophers, plural, got the primrose and it disappeared. How did they find it? The ground for more than 40 feet around the primrose is bare and had no gopher mounds of dirt. Nothing, yet the tunnel surfaced an inch from the plant and they proceeded to eat it. I set a trap and killed one gopher overnight, but the next day there was an additional mound and the plant had disappeared. Do they come above ground to scout around at night? I’m mystified.
A: Gophers are nocturnal so it makes sense that you could catch them overnight and lose plants to them at the same time. Their crescent-shaped mounds, tunnels, and plant damage are certainly signs they are present. Many animals find plants by smell and they may have been scouting above ground at night before building that part of the tunnel. While they feed on the roots primarily, they will also take whole plants underground. Continue trapping and try to exclude them from desired plants with hardware cloth buried beneath the beds.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: Can you help identify a shrub about 4 to 5 feet high, wide with fuzzy leaves, and a white umbrella flower? This photo shows what appears to be the seedpod.
A: It looks like Mexican olive (Cordia boissieri) and confirmed by our friends at the University of Arizona Herbarium. It’s native to southern Texas and can be found in the wild. It isn’t related to actual olives but it produces a similar looking fruit that isn’t palatable to humans but wildlife like them. The flowers are nice though so it makes a suitable landscape shrub/small tree if you have room for something that can grow to 30 feet given the proper accommodations. However, it doesn’t tolerate freezing temperatures.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: How do I keep cockroaches from invading my house from outside?
A: There are many species of cockroaches and only a few of them like to live with humans. For some species, entering your home is an accident and they can be dispatched with a broom. They are nocturnal and attracted to lights, water, food, and shelter. To protect your home, make sure it’s difficult for them to get inside by sealing any holes in the foundation, making sure door sweeps are in good condition, or traps can be used.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: My yard has a palo verde borer beetle infestation. I have personally smashed/stepped on/killed this many the last three years: 2014 – 54, 2015 — 53 (June 18-July 21), 2016 — 66 (June 19-July 31). I documented how many per night. And documented male/female numbers.Front yard has a 12-year-old Desert Museum palo verde with the most infestation. It lost a quarter of its branches this fall. Backyard has a 30-plus-year-old ash tree. In 2016, 28 of the 66 were from the ash. I tried two applications of beneficial nematodes (September 2015 and April 2016) with no reduction. Any help and suggestions are welcomed.
A: Palo verde beetles are typically an indicator of a stressed tree. They are often found when dead palo verde trees are removed but they are rarely responsible for the death of trees. Trees often die of multiple causes including the many environmental factors they are exposed to in our landscapes. It is usually these stresses and other factors unrelated to the beetles that cause tree death, even when the beetle larvae are present feeding on the roots. My suggestion is to make sure you are doing everything you can to care for your trees. This will go a long way toward protecting them from an early death. Beneficial nematodes are a wonderful thing in the right circumstances but there is no research I am aware of that shows they have any affect on palo verde beetle populations.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: Please — when you tell someone to water a tree down about 4 feet — will you please use other parameters? How am I supposed to know when something is wet down to 4 feet? Dig a hole? I didn’t read it today, and I can’t say that you are responsible for this — but many times past over the years I have had the same reaction. It’s just that today I am finally taking the time to write and your email address is handy!
A: Watering depth can be measured in several ways including some fairly sophisticated devices, calculating the output from your drip irrigation emitters, and by using a soil probe. The soil probe is the least complex and the least expensive. This device can be as simple as a piece of rebar with a handle and a pointed end. These probes are sold in a variety of garden shops and even our Cooperative Extension office sells them to benefit the Master Gardener Program. Some are as cheap as $5 and others are a bit more expensive. By pushing the probe into the soil after irrigating you can tell approximately how deep your water is going. The dry soil will provide more resistance than wet soil so you can stop pushing when it becomes more difficult and measure how much of your probe is in the soil. It’s not as much fun as math but it can help you adjust your irrigation practices.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: We purchased our home in Tucson Estates a few years ago. As part of the landscaping, there are bougainvillea plants along a fencerow. Every summer we have battled some kind of an insect that eats the green leaves. When we begin to have the cooler temps, the insects seem to be fewer and the plants finally begin to blossom a lovely red. With our recent warm temperatures, the insects are back in abundance. I’d really like to get on top of this before next spring so that we can have healthy plants and blossoms. Is there any hope? If so, what can we do?
A: There are two known caterpillar pests of bougainvillea. Disclisioprocta stellate, aka the bougainvillea looper and the somber carpet moth, is a moth originally from Africa that is now found commonly in Hawaii and the southern United States. The adult is a small brown moth and the caterpillar is also brown and small. Loopers crawl by arching their body into a loop shape so they are easy to identify while moving. Asciodes gordialis, aka the bougainvillea caterpillar moth, is also a small brown or tan moth found in the southern states. The caterpillar is green and doesn’t loop while crawling. Both of these insects will disappear in the cool part of the year and resume activity in the warm times. Identifying them would be useful and probably fun for me so I would like to know when they begin feeding again in the spring if you don’t mind. To manage them, you will use the same strategy. You can look for caterpillars now and whenever you start to see new damage and pick them off the leaves. They are helpless off the plants. You can also spray the leaves with Bacillus thuringiensis (Bt) labeled for caterpillar pests to kill the ones you overlooked. Looking more often when you notice new damage will help. There will be periods of time when they are less active when a quick weekly examination will suffice. The insect in the photo you sent is a green lacewing and is a beneficial insect that might help with your pest management. For this reason, the Bt is a good choice because it will harm only caterpillars.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren, Special to the Arizona Daily Star
Q: I have a question about our magnolia trees. It appears that one is dying and I am wondering if that is because the grass below them was removed. When the grass was there, the trees were very lush. Since the grass was removed and the ground covered with rock (and no water), it has changed the life of the magnolias.
A: I think you answered your own question. The tree was possibly receiving significant water from the grass irrigation. The fix for that would be to set up an irrigation system for the trees. A drip system arranged in a circular fashion around the drip line of the tree would be ideal. Non-native trees like the magnolia should be receiving 24 to 36 inches of water every two to three weeks in the winter. In the spring and fall, increase the frequency to 10 to 21 days and in the summer every seven to 14 days.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren, Special to the Arizona Daily Star
Q: Please advise if we can plant our hopseed bushes; foothills palo verde or desert museum palo verde; and “Leslie Roy” hybrid mesquites now. We’re concerned the weather might still be too cold. We’re thinking it might be better to wait for a few weeks, say third week of February. We live in Academy Village at Rincon Valley, southeast of Tucson, at an elevation of about 3,000 feet.
A: The cool part of the year is ideal for planting woody plants. They are dormant to some extent and less likely to experience transplant shock if the weather is cooler. The more time you allow the plant to become established in its new location before the summer heat begins, the better chance the plant will have to survive. Don’t put any fertilizer on them because you don’t want to stimulate new growth now. Also don’t prune them because it adds additional stress to the situation. If you need more information, the Arizona Community Tree Council has a nice and short tree-planting guide on their website.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren, Special to the Arizona Daily Star
Q: Several years ago I had a new evaporative cooler put on my roof — one that purges every few hours. The workman asked where I wanted the water to drain. I thought it would be great to use the water on some non-irrigated bushes below the roof. The man didn’t warn me that the water would be salty, and in time it would kill the bushes, which happened within a year. It’s been about four years since I’ve redirected the flow. Now I would like to plant gardenias in that area. I know they are sensitive to salt. I’m wondering if the rainwater draining off the roof has washed away the salt? I’ve imagined digging deep holes, throwing out the dirt and putting in garden soil. What do you think I should do? How deep and wide should I dig these holes? Would adding acid neutralize the salts?
A: If gardenias could choose their location, they would seek acid, moist, well-drained, high-organic-matter soils in a sunny but not too hot spot. Not exactly what we see commonly in Southern Arizona. That’s not saying you can’t grow them here but you will need to choose a good spot and maintain their surroundings to keep them alive and healthy. It’s best to have your soil tested if you are planning to plant non-natives to make sure they won’t be compromised from the start. My guess is the spot you chose is still salty unless you have been adding organic matter and giving it a good soak once a month to wash the salt through.The rainwater draining off the roof probably left salt in the soil when it evaporated. It’s hard to swap out your soil or change the characteristics of soil for more than a short time. Salinity, high pH and the lack of organic matter will be a going concern. If you are determined to grow these plants, the easiest way is to plant them in containers or raised beds with good soil. Since irrigation water is salty and so is fertilizer, you will still have to give the plants a good soak periodically to wash the salt through the soil. Keep an eye out for yellow leaves with green veins, which is a sign of nutrient deficiency. Also make sure to give them only northern or eastern exposure so they don’t bake in the desert sun.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren, Special to the Arizona Daily Star
Q: My yard is covered in “Horrible Evil Spiky Seeds of Death,” as we call them, though I’m sure that’s not the technical name. I think they come from the pictured tree. Humans can’t go outside without spending several minutes prying the damn things off their shoes. Dogs literally weep doggie tears to walk out there. Is this tree some kind of precious native specimen or can I burn it to the ground (metaphorically) without the stain of eco sin on my soul?
A: Your Horrible Evil Spiky Seeds of Death are also known as Tribulus terrestris, goat head, puncture vine and other words unsuitable for a family newspaper. They didn’t come from a tree but from a small green plant that grows prostrate to the ground. It’s a summer annual so all you see now are the seeds. Once they germinate and begin to grow, you will notice the green foliage and eventually the nice yellow flowers from whence the seeds develop. To step on a seed is very painful, as your dog would say if dogs spoke English. They are able to puncture some bicycle tires and so they are not well-liked by humans either. I switched to thicker tubes to reduce the number of flat tires. You can keep the tree and still wage war on the guilty plants by pulling them out of the ground as soon as you see them so they won’t produce more seed. Some people prefer to use an herbicide and any broadleaf variety will do. Please follow the label instructions for any pesticides you use to prevent injury to any non-target organisms.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: Recently we purchased pansies at Wal-Mart. They immediately wilted. I know they like to be in bright sun and so I placed them in an environment similar to what they were at Wal-Mart. Any suggestions to thrive? I’ve watered them when the soil is dry to touch and haven’t replanted them. Would like to think I have a green thumb. Probably not.
A: Pansies and violets (Viola species) are great for adding color to your landscape in the winter and spring. In general, they can be planted in sun (as long as it’s not too hot) or partial shade although some species prefer variations on this rule of thumb. If you look at a climate zone map, you might notice that it appears to be too hot for them in the Tucson area in the summer. They will look bad once the weather warms to their limit so we can treat them like annuals and replace them with something else. They also need water twice a day for the first couple weeks when they are getting established. This may be why yours wilted.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have researched and talked to many people about how to kill Bermuda grass most effectively while being as environmentally friendly as you can be. I have heard of several different methods, including covering the whole area in plastic as well as using Roundup as possible methods. I would like your opinion on the best method to use to kill Bermuda grass. My understanding is the only chemical way to do it would be with Roundup, but my wife is very against that idea. I have read the research on the biochemical makeup of Roundup and I am not sure if it is truly toxic if you only use that one to two times.
A: Roundup or any other product containing the active ingredient glyphosate is the most effective and least labor-intensive way to manage/kill Bermuda grass and many other weeds. It does require repeat applications and the grass needs to be green when you spray to be most effective. Other methods include scraping off the top layer of grass and covering it with landscape fabric, clear plastic, or cardboard, and digging the grass up with a shovel. You can certainly kill much of the grass through solarization, starvation, or digging it up. The problem, as you may know, is the roots, or parts of them, are still alive in the soil in many cases with all of these methods. They will eventually find a way around or through the covers so it may be more labor intensive to manage it. Bermuda grass spreads by underground stems (rhizomes) and aboveground runners (stolons), not to mention seed. A systemic herbicide can get to the root of the problem with less effort. No matter which method you choose, if you live in an area with unmanaged Bermuda grass nearby, it will eventually return so you need to remain vigilant in your management. Regarding the toxicity, according to the Monsanto label, glyphosate is a moderate irritant if eyes and skin are exposed but is practically nontoxic otherwise unless you are an aquatic organism. As always, it is best to follow the instructions on the label of any pesticide to avoid harming any non-target organisms.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I read your article about Bermuda grass and have a question concerning the condo development where we live. The complex includes a large area of grass and mesquite trees. The HOA overseeds in the winter. This makes for a beautiful green area and also greatly cuts down on blowing dust. The landscaping company has advised the HOA to not overseed every three years to help the Bermuda grass. Does this make sense to you? I see many places (e.g. golf courses) that overseed every year and the Bermuda grass appears to come in just fine.
A: Yes, it makes sense. Continuous overseeding can cause stress to Bermuda grass if proper care is not taken for proper overseeding timing/preparation and proper spring transition back to healthy Bermuda grass conditions. Rye grass is a common cool season grass used to overseed Bermuda grass in the fall. Extended rye grass seasons on the front end from early overseeding and well beyond spring transition into summer will weaken the root system and reproductive capabilities of Bermuda grass. If these unhealthy practices are repeated annually, exhausted and stressed Bermuda grass diminishes over time and requires renovation. Thus, skipping overseeding every few years can provide the Bermuda grass a nice long growing season from March to November to rebuild roots. If the stress is minimized by best management practices and a good 100 days of optimal growing conditions are provided each year, Bermuda grass can be overseeded regularly. The minimum 100 days should be in the June through September timeframe. For more details on the timing and preparation, there is a nice publication available online by the University of Arizona turf grass specialists, David Kopec and Kai Umeda.
Peter L. Warren is the Forest Health Program Coordinator for the Arizona Department of Forestry and Fire Management. Questions, photos and videos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have a mature grapefruit tree I have been maintaining for three years ago. I keep it watered, fertilized and trimmed. It has always given me many wonderful juicy pink grapefruit, which I love, and share with friends. This spring, I noticed very few blossoms and now there are very few (probably less than 50 total) grapefruit on the tree. The existing fruit has extremely thick rinds, about 1ƒ inches thick, leaving very little room for the inside fruit. Did I do something wrong to have this problem? I love this tree and the fruit and would appreciate any help you can give me to do whatever it takes to bring back the bounty come next spring.
A: I recommend you double-check the fertilizer amount, timing, and type you are supplying. Over time, trees with an imbalance of nutrients may develop thick rinds. Nitrogen is often the main ingredient in fertilizer but trees also need a small amount of phosphorus and potassium. There are some fertilizers designed and sold for citrus. If you aren’t already using one of these, it might be worth switching. You also might also double-check the watering schedule to make sure that is correct. It should be every 14 to 21 days to a depth of 36 inches in the winter, every 10 to 14 days in the spring and fall, and every seven to 10 days in the summer. Trimming your citrus tree is not something recommended unless there are dead or damaged branches.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have a Mexican palm that is about 25 feet high and still growing. Is there any way to slow it down or stop it from growing? Also it is 6 feet from an in-ground pool and 2 feet from brick wall. Should I be concerned about this?
A: Palm trees, like other tree species, tend to slow down growth when they receive less water. You can’t stop it from growing unless you use a chainsaw. Trees growing too close to structures can be a problem as their roots grow and seek water. I think your description warrants a visit from a certified arborist to determine the gravity of your situation. Palm trees are not as big a problem as some other trees that have larger root systems but they can still disrupt hard structures over time.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I think it’s nearly time to begin pruning my grapevines (two Red Flame and one Thompson green) and seems like it’s a good idea to address last year’s pests. Although the photo shows the arbor in shade, the vines get six to eight hours of sun daily. In the summer, the drip system provides each vine with one gallon per hour, four days a week, for an hour and a half. And last summer, boy did we have bugs. I use Bt for one kind of caterpillar that has been with us since the beginning, coming up on four years, but it didn’t seem to faze them. I’d prefer a systemic, because our monsoons wash sprays off. I’m happy to forgo harvesting grapes for another year or two. What is your recommendation?
A: Bt (Bacillus thuringiensis) is helpful in managing caterpillars such as the grape leaf skeletonizer (Harrisina brillians). Bt doesn’t have any affect on the various species of leafhoppers that are causing the damage in the photo. Leafhoppers suck the sap from leaf cells causing the yellow appearance you are seeing. Grape plants can withstand a good amount of feeding damage before fruit yield is affected so you might not have to do anything. There are also natural enemies that feed on the leafhoppers so you probably already have some help managing them. If you want to determine if treatment is recommended, you can monitor the population by counting the number of leafhoppers per leaf on a random sample of leaves. If the number per leaf exceeds 15, then it might be worth treating. There are systemic insecticides available for this purpose and they can be applied as a soil drench. Active ingredients for these chemicals are toxic to bees and other animals so please follow label instructions if you go this route. So my recommendation is to assess the situation before treating because you might save money by monitoring them this spring.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: We live on a property in the near foothills on the east side of town that has a number of saguaros. There is one cactus that we’d always assumed was just an odd looking saguaro because it is about the same size as many of the saguaros in our yard. This morning, we noticed that it has two blooms and they are quite different from those on saguaros. We also realized that while the spines are similar to those on a saguaro, they differ too. Can you help us identify this cactus?
A: From your photo this appears to be an Argentine saguaro (Echinopsis terscheckii), aka cordon grande. This species is sometimes planted in our area for its ability to withstand cold weather. It grows faster than the native saguaro and is hardier so it can be grown in slightly colder climates. As you noticed, the flowers look more like a cereus than a saguaro and the spines are longer as well.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: This fall I found I had holes in my tomatoes. I cut some open and there were some kind of brown hard stuff in the fruit. Any idea what they are?
A: The signs indicate tomato fruitworm (Helicoverpa zea) damage. These insects are fairly common and also known as corn earworms and cotton bollworms, depending on the crop where they are found. The eggs are laid on the plant and the larvae bore into the fruit where they can stay until they complete their development and drop to the soil to pupate. The brown stuff is probably frass (caterpillar poop). These insects are difficult to manage once inside the fruit so it is best to catch them before they enter and/or dispose of infested fruit before they have a chance to emerge. Lima beans can be used as a trap crop because they prefer them to tomatoes. There are also pheromone traps available to monitor when the adults are flying so you can tell when to start looking.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: You recently provided some info on fertilizing citrus and I have located the chart you referenced. You often recommend watering to a depth of 36 inches, so I’ve been using a deep watering rod on my three mature fruit trees (10-12 feet, grapefruit, lemon, and orange). What is the preferred method for applying fertilizer? Should I use a pre-mixer with the watering rod below grade or apply the fertilizer on the surrounding ground under the tree and soak it from the top down?
A: The preferred method of fertilization is to spread it around the drip line of the tree and water it into the soil as you described. This is also the preferred method for irrigation so you can do both at the same time. I don’t recommend the deep watering rod because it likely bypasses some or many of the absorbing roots of the tree, which are typically in the top 1 to 2 feet of soil.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: We have two Texas Ranger bushes that are each about 5 feet tall. We were at a local nursery recently to get some information about trimming our trees and the subject of cutting back the bushes came up. The person at the nursery suggested cutting the bushes down this February to only 1 foot high, straight across (almost like a flat-top haircut). That seemed pretty drastic to me and I wanted to get your opinion.
A: What your nursery person described is called renovation pruning and it is appropriate for some situations such as when shrubs become too large and you want to improve their aesthetic value. It is a drastic method and shouldn’t be pruned this way every year because it is stressful for the plant. It also works best if you are able and willing to follow up the buzz cut with some selective pruning a few months later. The initial severe cutting of all branches to 12-18 inches above ground will cause a flush of growth in the spring and into the summer. Once this happens it is best to follow up with the selective removal of about 50 percent of the branches at the base to thin out the canopy. Then prune the tops of the remaining branches to different heights, making sure to prune just above outward facing buds to encourage healthy branching to the outside of the plant. If this still seems too drastic or you aren’t interested in cutting your shrubs down to size, you could simply do the selective pruning part without cutting all branches back to the 1-foot level.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
- By Peter L. Warren Special to the Arizona Daily Star
Q: I have two Meyer Lemon trees, bought and planted at the same time. One is in the back yard where it gets lots of sun. The other, in the side yard, only gets partial midday sun. The leaves on the side-yard tree are yellow and the tree bears little fruit while the other, although shaded by a large evergreen tree, has flourished and looks healthy except for a back branch which is turning yellow. Can you offer any suggestions as to the cause of this situation?
A: I think you may have answered your own question, assuming your trees are otherwise healthy and receiving proper water and nutrients. Citrus trees need full sun to be at their best. From your description, the healthier tree is getting “lots” and the side yard only gets partial sun. The ideal would be eight hours of sun and that is not possible with only midday sun. Since “lots” is not a number, I will guess that even the tree in the backyard could do better if your large evergreen tree didn’t shade it. If it’s not possible to change the surroundings to allow more sun on the trees, you might consider moving them to a sunnier spot.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
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