Over the last couple months, homeowners across the state have been calling the Infoline wondering why the leaves never fell from their Japanese maples this fall (Acer palmatum). Although this may seem like something to worry about, it’s a fairly common occurrence, and in most cases is nothing to worry about. The trees are simply exhibiting marcescence, the trait of holding on to dead plant tissue; in this case, leaves. When a tree prepares to shed its leaves, cells between the twig and leaf stem release enzymes that form an abscission layer which releases the leaf. Sometimes leaves form incomplete abscission layers, causing the leaves to stay attached to the branches. This is common for many species such as beeches and oaks.
The long, mild fall of 2017 may have contributed to the maple’s leaf retention. Even during an average fall, Japanese maples are often one of the last trees to change color. It just takes them much longer to prepare for winter than other tree species. The abnormally warm temperatures in the fall that lasted through October, may have caused many Japanese maples to never form the complete abscission layers necessary for the leaves to drop. Thus, when the cold weather finally came, the leaves were still attached to the trees.
Ultimately, you shouldn’t worry too much about those stubborn leaves. What the wind doesn’t remove will be pushed off by expanding buds in the spring.
This was your Question of the Week. Got questions? The Ask UNH Extension Infoline offers practical help finding answers for your home, yard, and garden questions. Call toll free at 1-877-398-4769, Monday to Friday, 9 a.m. to 2 p.m., or e-mail us at answers@unh.edu.
