|I have two large dogwoods that have many leaves that are turning yellow and falling off. There is, however, no problem with other dogwoods. Could this be due to to lack of fertilization (the past two years have had very few blooms), or due to the extremely hot weather lately with no rain, or due to Verticillium wilt?|
|Dogwoods do not like hot, dry weather, so I'd bet the heat is weakening the plants, if not actually causing the leaf yellowing. There are a number of possible diseases, including an anthracnose disease that is becoming more and more of a problem. Symptoms include small, purple-rimmed leaf spots or large tan blotches--these spots may enlarge to kill the entire leaf.
The trees like cool, moist soil, so I would be sure to water the plants during hot spells, and mulch with a thick layer of organic mulch (keeping the mulch a few inches away from the trunk.) On the other hand, the tree does not like heavy, poorly drained soils and will decline over the years in such conditions.
I doubt the problem is due to lack of fertilization, and if the plant is truly declining, I would hold off on fertilizing--it's best to fertilize an actively growing plant. I would inspect the plant carefully for signs of disease such as those described above, as well as insect pests. If you find any specific signs, you might bring them in a sealed bag to a local nursery or arborist for help in identifying the culprit.