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Red oak with marcescent foliage
Red oak without marcescense

Why do some deciduous trees hold onto their brown leaves all winter?

The condition is called marcescence. It literally means “withering but persistent". For plants that means that leaves turn brown in the fall but stay on the tree through the winter and release in the spring when bud swelling of the upcoming new growth pushes the old leaves off.

Deciduous trees form an “abscission zone” at the base of each leaf stem that allows leaves to fall off the twigs. Trees such as some red oaks, post oaks, pin oaks, white oaks, Caddo maples and others don’t allow this to happen until closer to spring. Are the dead leaves clinging to their trees. Or - are the trees clinging to their dead leaves. Theories for this clinging range from deer browse protection, to delay of leaf decomposition once on the ground, to plant immaturity since marcescence seems to be more common on younger trees.

Some experts suggest that marcescence helps trees growing on dry, infertile sites, thinking that holding leaves until spring could be slowing the decomposition of leaves and that dropping them in spring puts organic material on the soil when it is most needed. Even small amounts at the right time could shift the competitive advantage toward these trees on poor sites.

Caddo maple with marcescence (above and below)

Others suggest that retained leaves, especially on young trees and the lower branches on bigger trees, are an effective means of trapping rain or snow for more moisture at the base of the trees come spring. Still others have suggested that persistent leaves might provide some frost protection for buds and new twigs over winter. At least one study suggests that marcescent foliage could be a deterrent to browsing by deer and other wildlife. Buds hidden by dead leaves are protected and live to become new growth in the spring.

Camby oak showing it’s mid-winter semi-deciduous characteristic

A related condition is called semi- deciduous. Trees with this factor hold some green leaves throughout the winter releasing the dead leaves over a period of time. The fall color of these trees is spotty and inconsistent. Water oak, willow oak, Canby oak and others are in this category. And of course some evergreen trees hold their green foliage basically all winter and kick them all off in the spring when the new buds swell.

The bad news is that the trees have conspired to give us leaves on the ground to manage year round. There’s nothing you can do about it and I think the interest is worth the trouble.


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