Question: My yard is covered in “Horrible Evil Spikey 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?
Answer: Your Horrible Evil Spikey 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.
Question: 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?
Answer: 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.
Question: 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.
Answer: 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.
Question: 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.
Answer: 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.
