Difference in fall leaf drop by location
I live in Ann Arbor and all of the leaves have now (Nov 15th) fallen off the deciduous trees. I was in Dearborn on Nov. 13th and a lot of the trees still had their leaves on them- especially it seems the maple trees! Does Dearborn have a weird microclimate that has kept the leaves from falling off the trees??
Wayne County Michigan
Our office in Ann Arbor has serviceberry trees that did not drop their leaves . I have seen many red maples and Japanese maples, in my travels, from Detroit to Jackson that did not go through the normal leaf drop. Leaf drop is associated with a hormone, abscisic acid, that develops within the plant. As environmental conditions change in the fall, this hormone is sent to sites where the leaf petiole is attached to the plant. It causes an abscission layer to form that separates the leaf petiole from the branch causing leaves to drop. This process did not fully transpire for some plants as temperatures dropped quickly. Two or three years ago we had the same thing happen with Japanese maples across the State. A large number of leaves remained on the plants into the winter and in some cases into early spring and they dropped as buds began to develop. It did not harm the trees. You may be right that a local site condition may have something to do with this but I cannot see any clear significance between sites where this is occurring. The good news is that plants will be fine.