After being asked a question recently about trees, I did some research, learned a new word and gained some understanding of deciduous trees.
Why does this tree still have leaves on it while the other ones just like it are bare? I have noticed this tendency but never knew it had a name. It’s called “marcescence.”
To really understand how a tree loses its leaves, you have to go down to the cellular level. In simple terms, for a leaf to fall off, the cells at the point where the twig and the leaf stem meet produce an enzyme and form an abscission, causing leaf drop.
If an outside condition, such as a rapid freeze, interferes with this process, some or most of the leaves might hang on throughout the winter until spring, when new buds form and the older, dead leaves will be forced off.
Is it a bad thing for a tree to keep its dead leaves hanging on? I spoke with a local arborist who emphasized the timing of when the leaves turn brown and hang on tells more about the health of the tree.
If a tree’s leaves turn brown in the summer or early fall and the leaves hang on, this could be a sign that the tree is stressed or unhealthy. A hardy, healthy tree that has encountered something harmful will shed its leaves and be bare, aiding in its survival.
By late fall, once the leaves changed colors, whether the dead leaves hang on or fall off is not necessarily an indication of anything except the natural predisposition of that particular tree.
Certain species of trees have a greater tendency to hold dead leaves all winter, including beech and a few types of oaks. Other trees and shrubs, such as some crepe myrtles, may hold their dead leaves until spring.
Some researchers studying marcescence say younger trees, understory trees and those planted in drier soils tend to retain dead leaves. Others claim that highly adapted trees will have marcescent leaves to protect them from being eaten by wildlife or to provide more nutrients in the soil in the spring.
Darla Horner Menking is a Texas Master Gardener and Master Naturalist. Contact her at firstname.lastname@example.org