Question: I planted two Chaste trees (Vitex) in the spring and in October the leaves started to turn yellow. Now the tree's leaves are almost all gone. I have pine bark covering the ground around the tree's base since I planted them. Is this supposed to happen? I'm concerned because I noticed that my neighbor's chaste tree is still green. The nursery spokesperson told me this was normal because the trees go dormant. I'm just puzzled since when I drive around my part of town I see other chaste trees with their leaves still green.
Answer: It could be normal. Then again it could have just coincidentally died and it will drop its leaves as well. It is normal for Chaste tree to drop its leaves this time of year. There are at least three reasons why your Vitex could drop its leaves early.
One is that your tree may not have been fertilized as much as others. Nitrogen fertilizers will delay the onset of leaf drop in the fall. When plants receive lots of fertilizer, particularly nitrogen, late in the season their leaf drop is delayed and they will go dormant later in the season.
This delay of dormancy happens with all plants including grasses. Bermudagrass lawns will go dormant or turn brown later in the fall if they get late summer fertilization. Tall fescue lawns are less likely to become brown during cold weather if they get a fertilizer application high in nitrogen around Thanksgiving. Applying nitrogen fertilizer in the fall can be good and bad. This can be good because you can enjoy your plant longer in the fall. If you apply the fertilizer just before the leaves turn color you can store nutrients in the tree that will be carried over to the next spring and skip a spring fertilizer application. It can be bad because it also decreases the plants ability to tolerate cold temperatures that might damage it.
Secondly your Vitex may be less tolerant of cold temperatures than others. This happens frequently to plants that are started by seed in the nursery. Plants that are started by cuttings are more likely to be consistent in their leaf drop since they are clones.
Thirdly your tree could have been in bad health. Trees in poor health or under stress may drop their leaves earlier than others in better health. Normally you would have seen signs the three was not doing well. This could have been small amounts of new growth, poor leaf color during the summer, smaller blooms, some branch dieback.
You can check the tree to see if it is still alive by bending some growth from this past year and checking to see if it is supple (still has moisture and can bend). This past year's growth should not break easily when bent. Using your thumbnail, the outer bark of new growth should easily be scraped from the branches and reveal healthy wood under this thin outer layer.
Next year make sure it is watered deeply and not frequently. Do not water daily. It should be watered with the same frequency as other desert tolerant trees and shrubs.
Q: I purchased the dwarf oleanders two years ago in five gallon containers. They are doing fine, but are about four feet high. It is my understanding the plants can be pruned. I need to know the best time to do so and how far down to go without harming them.
A: These are young plants but they still could benefit from some selective pruning. Pruning oleander is very simple, much simpler than many other plants and you can prune them any time of the year without any problems. The incorrect way is to use hedge shears.
Count the number of main stems coming from the base of the plant that are the oldest (largest in diameter). Remove one third of these larger stems as low as possible. You are done! You will do this about every two or three years. No hedge shears. It takes about ten minutes and no mess to clean up.
If there are some unusually long stems, remove them from the base as well. Having said this, the absolute best time to do this is February and March but you can do it any time.
Q: We are considering an automatic fertilizer but have some questions and thought you might be able to help us. Our current drip system only has two zones, one for the front and one side and the second zone for the back and one side. All plants were planted in good soils. When we install a fertilizer system, what should we be trying to control, pH, alkalinity, pests? Or do you use different fertilizers at different times of the year? We have neighbors who had a system installed, and cannot find the product to continue to use. The company that installed is no longer in business.
A: The fertilizer injector, as the name implies, is primarily for applying fertilizers. I would not recommend injecting pesticides into a drip irrigation system that is not commercial.
Commercial operations generally are fertilizing or controlling pests of a single crop or type of plant. You are not. When you inject a pesticide it will go to everything, regardless of whether they have pests or not. Not a good idea.
I personally do not even think a home fertilizer injector is a good idea in most cases unless you have a very large property and lots of plants. Fertilizer injectors are only as good as the irrigation system. If the irrigation system was not installed well, then of course the fertilizers and pesticides will not be applied correctly. They are really intended for commercial use and systems designed to handle fertilizers and pesticides.
You can apply fertilizers to plants by placing them just under the emitter. This can be a bulk granular fertilizer or fertilizer stakes, whichever is more convenient. You can do the same thing with granular, soil applied pesticides if you wish.
You can avoid soil applied fertilizers and pesticides by applying these as foliar sprays, spraying the fertilizer directly on the leaves.
In the future you might redesign the drip system as these plants get bigger and watering becomes more complicated. I like the fact that the system was divided so that the front is paired with one side and the back with another side. Ideally the West side should be paired with the South side and the North side with the east side if they are paired at all.
Please make sure that you have adequate backflow prevention on your irrigation system before installing any kind of injector. If you inject any kind of fertilizer or pesticide there is a chance that this can get flushed back into your drinking water in the home or into the community water supply.
I would find the manufacturers label on the unit and contact them for their suggestions on which type of fertilizer to use. There is at least one supplier in Las Vegas who does carry fertilizers made for injecting. Check your yellow pages and if you cannot find them, let me know and I can direct you further. Unless the fertilizer label says it can be injected, I would not do it. You could be faced with hours of cleaning emitters, or replacing them, if the fertilizer does not work right.
Bob Morris is a horticulture specialist with the University of Nevada Cooperative Extension.
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