I had a question from someone who was concerned that their cherry tree and crab apple tree lost all their leaves during the summer. The quick response is that it is probably a result of environmental conditions and is something that you don’t have to worry about.
Trees adapt to their environmental conditions. If we look back to our spring and early summer, it was very wet and the temperatures were moderate. The tree sees this as ideal growing conditions and responds by growing lots of leaves. When the rain stopped and our normal summer heat hit, the tree responded by losing leaves because suddenly it was too hot and dry to sustain so many leaves.
Unless this happens for several years in a row, the trees adjustment to heat and dry weather doesn’t effect the overall health of the tree. Remember however, that newly planted trees are more susceptible to leaf drop as their roots are not as well formed. Newly planted trees must be watered regularily.
Leaf drop can be caused by disease as well. These diseases can also be brought on by the wet spring, hot summer. The difference will be that the leaves will have spots or brown areas. If this is the case, be sure to rake up all leaves and dispose of them (not in the compost).
Water your trees in dry periods and do not fertilize until fall.
If you notice that the twigs and branches of the tree are dying, you might have a bigger problem. A loss of more than 50% of a tree’s leaves two years in a row may also give you further cause for concern.