|I have two sets of Holly bushes in front of my house. One set is doing fine, yet the other is turning yellow. They are only about ten feet from each other and the bushes around and in between are doing fine. All of the bushes were planted in 1991 so they are well established. We are in the middle of a heat wave, but they are getting watered regularly once a week and I don't understand why one set is doing fine and the other is not.|
A good article. there are two kinds of Holly the American holly drops it's leaves
|Holly Bushes. If the yellowing is occurring on the new growth (younger leaves or those toward the ends of the branch or shoot), the problem is probably iron deficiency brought on by high soil pH levels. Irons chelate products and applying sulfur to the soil to lower pH are two good ways to remedy the situation.
If the yellowing is on older leaves it may be due to scale insects. Look under the leaves for a whitish, flakey substance or tan, round things about the size of a typed lowercase "o". Scale feed primarily on the underside but cause a yellowing on the top surface when they occur in large numbers. Summer or horticultural oil sprays (not dormant oil) applied upward from beneath the plant can effectively control scale. Make sure and spray early in the morning when it is cool. If possible do your spraying in the spring and fall as oil sprays can burn foliage in the heat of summer.
A final possibility would be damage from a herbicide application. Sometimes even a weed-and-feed fertilizer applied to the turf can affect shrubs and trees with roots in the area. There is little you can do after the fact except to watch and wait. The bush will likely recover if the damage is minor.
Hope this helps!