Scientists Say: Marcescence

Marcescence (noun, “mar-SES-sense”)

Marcescence is when a plant clings to its dry autumn leaves through the winter.

As summer turns to autumn, the leaves of many trees wither and fall. But some trees hold onto their leaves straight through until spring. Scientists describe trees with this unusual quality as marcescent.

Deciduous trees, such as maple and beech, carry out the familiar seasonal cycle. New leaves bud in spring. Those leaves mature through summer, then die in the autumn and break away. Think of marcescent trees as a special case of deciduous tree — one that skips that last step. Rather than dropping, the leaves of a marcescent tree hang on until wind or another force knocks them down.

We see examples of marcescence in trees such as oak, some willows and beech trees. As fall approaches, the leaves of a beech tree die, just like those of any deciduous tree. Their lime green leaves turn orangey-gold. Then they cling to their branch tip and rattle in the cold wind all winter long. Eventually, a strong force — such as wind — may break them off. Other times, they just crumble away bit by bit.

The reason for this odd plant behavior remains unclear. But scientists have theories.

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Marcescence may help protect against hungry herbivores. Deer, for instance. During winter, food is scarce and hungry deer chomp away at tender new branches of young trees. The unappetizing dead leaves of marcescent trees may deter deer from snacking. Another theory is that dead leaf clusters provide a physical barrier that the deer must chew through to reach the juicy new growth underneath.

Studies suggest that trees clinging to their dead leaves helps control how quickly those leaves break down. Therefore, marcescence may affect how fast nutrients return to the soil.

In a sentence

Marcescence may help to protect young trees against hungry herbivores.

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