This time of year we have an unparalleled opportunity to look into our trees future.
Like fortune tellers you can use your powers of observation to predict the future health of your trees and shrubs. Most trees and shrubs lose their leaves at this time of year. Even evergreens lose some leaves at certain times of the year. When and how much of their foliage is lost can give you a window on the future when it comes to the plants health.
Deciduous trees loose their leaves in a set order governed by day length, genetics and most importantly tree health. Ash trees typically lose their leaves sooner than oak trees or most maples. Within a group of trees of the same species individuals will loose their leaves at approximately the same time. Trees that loose their leaves sooner than their kin may be under stress. Insects, disease and drought can cause trees to loose their leaves prematurely. If you take the time to watch your trees at this time you may be able to identify individuals that are at risk and take action.
Birch trees that loose their leaves prematurely may have birch borers and there may still be time to treat them before next spring. Elm trees that loose their leaves prematurely may have late season infections of Dutch Elm Disease and can still be tested to see if they should be removed. Maples that are infected with verticilium wilt may have been struggling all summer and heat, combined with late season drought may have pushed your tree over the edge.
The process of losing leaves takes energy. Trees must form abscission layers at the base of the petiole, where each leaf stem meets the tree. If the tree is to weak or too diseased to form this layer it will not drop its leaves, they will simply wilt and hang on the tree. This symptom called flagging, is usually a sign that the tree has expired.
In nature there is a lot of variation between individuals of the same species and even more variation between different species. A good example of this is how some white oak species will retain a significant portion of their leaves right through winter. For white oaks this means very little. If your elm tree did the same it may have Dutch Elm Disease.
Occasionally you will have an early frost and trees will lose their leaves quite suddenly resulting in many still being left on the trees. Not to worry this is just an unusual occurrence and most trees are close to losing their leaves any way and will do so shortly even if the leaves have been frosted.
If summer continues and the first frost is a few weeks or even a month late, the trees will lose their leaves before the first frost. The wheels of change are moving as we approach winter. Take this brief opportunity to look into the future and see how healthy your trees will be next year. You may still be able to help your stressed tree get onto the road to recovery. If you are unsure of your trees health status contact your certified arborist.