Q: I have a Meyer lemon plant in my house waiting for the temperatures to drop. I’m using grow lights. When can I plant it again?
A: This depends on the size and health of your Meyer lemon, as well as the ambient temperature. Usually this means waiting until fall (October) or spring (late January). Of course, the experts at the plant shop will tell you: “Any time of year is good for planting.”
FYI: Depending on the plant and the size of their stems, plants can continue to grow without additional light. If your plants are large and healthy and receive enough light, they will store extra nutrients in the thickness of their stems or branches.
For some large houseplants, nutrient reserves can last for three to four months at cooler temperatures in low light conditions. Of course, at higher temperatures, this extra nutrient supply is quickly used up.
Q: A few months ago I saw this 5-20-5 fertilizer and thought I’d give it a try. The stuff works a week after application and lasts about three weeks. I’m wondering how the soil affects these chemical fertilizers and how the plants benefit. My west-facing Arabian jasmine is doing better than it should.
A: I have a theory: plants in better health can withstand more adverse conditions than those in worse health. I also believe that some fertilizers contain organic matter that is more beneficial to most plants growing in the desert than to our untouched soil. But your fertilizer does not appear to contain any soil organic matter.
Plant health can often be a gamble, especially with fertilizers. It is known that soil organic content has a major impact on fertilizer effectiveness.
For Arabian Jasmine, the organic content of your soil should be high enough for fertilizers to be effective. (The organic content of a soil is usually related to its color. The same is true for fertilizers that contain soil.)
Q: Five years ago, we purchased our home with 10 mature Mexican palms and 10 mature oleanders alternating on two sides of the pool. The roots of the palms first lifted the concrete pool deck on the south side, necessitating the removal of five trees, and now the roots of the five remaining palms have begun to damage the deck. They are scheduled to be removed to about 6 inches below grade next week. We would like to fill the spaces with shrubs or trees to regain some of the height and privacy, but without repeating the potential root damage. Please let us know if we have any concerns about leaving and planting oleanders in the 4-foot space between the concrete deck and the 6-foot wall. If you recommend removing the existing plants, please suggest alternatives.
A: Choose plants that are not very tall when fully grown. Palms do not usually cause problems along walls, foundations, walkways or patios unless planted too close to them. Remember that in most soils (unless it is clay), irrigation water will keep the soil moist about 10 to 12 inches from where it is applied. A general rule: if palms are placed 4 to 5 feet away from these hard surfaces and watered on the opposite side of a potential problem area, they will not lift a cool patio. This is also true of the standard oleander, mainly because of its height of about 15 feet.
If you have serious concerns, talk to your homeowners association’s landscaping committee.
If you are planting near a hardscape, always place the water on the side of the plant facing away from the hardscape, not between the plant and the hardscape. This encourages the roots to grow away from the cool deck. If there is hardscape on both sides of the plant, place the watering as close to the center as possible so the roots grow there and not under the structures. Otherwise, use smaller plants that will add some color.
Q: I previously sent you two questions about my fig tree and a palo verde that was oozing sap from its branch. I then dug up the fig tree and sifted through the soil and found larvae feeding on the roots. So it was not watering as you suspected. I mixed diatomaceous earth into the soil when I planted it. As for the palo verde, I had the tree on a dripper when I planted it but later covered it after it was established on the advice of my landscaper. I have watered it thoroughly about half a dozen times a year for the past 18 years. Any other suggestions would be helpful.
A: The palo verde is native to the Sonoran Desert, but the fig tree is not. Figs are temperate fruit trees and should be watered more frequently. Your landscaper was right to stop watering the palo verde as often since it is a desert tree.
What type of palo verde was it? The blue palo verde develops deeper roots and thrives when watered deeply but infrequently. This is not usually the case with the foothill palo verde.
After establishment in the spring, I water the Palo Verde thoroughly once every two to three weeks during the summer. The watered area is increased as the tree grows larger. Both trees are eventually watered to at least half the crown diameter. The fig tree should be watered every other day during the summer. Both trees can grow to about the same size.
I’m surprised to hear that you found larvae feeding on the roots. Often these are compost larvae that do not eat the roots. Make sure you see larvae feeding on the roots and not on organic matter in the soil. Or have an entomologist identify them.
Depending on the larva, some feed on living plant roots, while others are mainly decomposers and generally do not pose a major problem to plant roots.
In my opinion, it is still a watering problem. Larvae do not usually harm the plant (unless there are a lot of them feeding), but by feeding they limit the amount of water that reaches the leaves and stems.
Diatomaceous earth has no effect on larvae in soil. To be effective, diatomaceous earth must remain dry, so if you mix it into moist soil, it will have no effect on the larvae. Depending on the type of larvae involved, beneficial nematodes may be a good option.
Bob Morris is a horticulture expert and professor emeritus at UNLV. Visit his blog at xtremehorticulture.blogspot.com. Send questions to [email protected].
