What can cause ornamental pear trees to hang onto their foliage in the winter?
In the fall, trees normally form what’s known as an “abscission layer” at the base of the leaf stalk (petiole) that causes the leaf to fall from the tree. In the fall, with lower night temperatures and shorter days, leaves begin to decline as chlorophyll breaks down, and cell walls weaken at the base of the petiole in the abscission zone. In addition, leaves discontinue production of a plant hormone that helps hold these cells together. The result is that leaves fall from the tree. Unusual weather in the fall can disrupt the normal development of the abscission layer in ornamental pears and prevent cells from breaking down. If that happens, wind or other physical forces will have to knock the leaves from the trees. Trees should leaf out normally in the spring, since buds for this season were set late last summer.
