Have you noticed the persistent brown leaves still hanging on some deciduous trees long after their foliar companions have fallen? This usually becomes very apparent after normal leaf drop in early winter. These brown leaves may remain attached until spring bud growth pushes them free.
Older deciduous trees typically drop all of their foliage, but more juvenile trees of some species may hold onto all or a portion of their foliage.
Joey Williamson, ©2019 HGIC, Clemson Extension
Complete leaf drop (abscission) may not occur on some trees until spring, or they may drop from all but lower limbs on other tree species. This is foliar marcescence, which comes from the Latin, marcescere, and means “to fade”. The persistent leaf does not readily form an abscission layer at the base of the leaf petiole (leaf stalk), where it attaches to the twig. This allows these brown leaves to remain attached on trees much longer.
This juvenile oak tree continues to hold onto its leaves into February. Joey Williamson, ©2019 HGIC, Clemson Extension
Typically, leaf marcescence is seen on oaks (Quercus species), American beech (Fagus grandifolia), hornbeam (Carpinus caroliniana), Eastern hophornbeam (Ostrya virginiana), and witchhazels (Hamamelis species). However, depending upon the weather, it is infrequently seen on other species.
The marcescent characteristic is more pronounced on younger trees, but may be seen only on the lower, more juvenile limbs of larger, more mature trees, especially oaks. However, a long warm autumn that is quickly followed by the onset of cold weather will prevent the formation of this abscission layer on other tree species, as is frequently observed on maples.
Cold autumn temperatures caused the more juvenile lower limbs of this red maple to hold onto their leaves.
Joey Williamson, ©2019 HGIC, Clemson Extension
A question that arises, though, does this marcescence benefit the trees or is it a detriment? Indeed, strong winter winds and snow may have a more harmful effect on a tree possessing foliage by causing more branch breakage. However, several theories proposed by plant ecologists suggest that leaves that drop later in the spring will provide a fresh layer of leaf mulch around the tree that helps conserve soil moisture, and these leaves decompose later during springtime to recycle and provide additional nutrients for growth. Another theory that seems to make sense is that lower limbs holding onto these dry unpalatable leaves may deter browsing by deer, who prefer to feed on the more tender and nutritious buds and twigs, not on the bitter, fibrous old foliage.
Whatever the reason for the marcescence, it is an interesting characteristic to see, and if you listen closely, you can hear these noisy, rattling leaves during the winter breezes.
For more information of autumn foliage, see: HGIC 1029, Color Changes in Autumn Leaves.
There is a very moving fable for children and adults about a leaf, possibly marcescent, that is afraid to let go and fall called The Fall of Freddy the Leaf, by Leo Buscaglia, Ph.D.
