“Nature now, like an athlete, begins to strip herself in earnest for her contest with her great antagonist, Winter. In the bare trees and twigs, what a display of muscle.”
— Henry David Thoreau
Have you ever wondered why trees lose all of their leaves in winter? Here in the Lowcountry, we have a lot of evergreen trees that don’t lose their leaves. However, away from the immediate coastal region, maples, oaks, sweetgum, cypress, sycamore and tupelo provide seasonal color in the fall and lose their leaves in winter.
Unlike animal cells, plant cells contain a great deal of water, stored in vacuoles within each cell wall. When these cells freeze, the water stored inside them expands into ice crystals, which puncture the cell wall and collapse the cell. In order to protect themselves from this eventuality, deciduous trees lose their leaves ahead of winter.
Trees that lose their leaves are susceptible to freezing winter temperatures because of their leaf shape, which tends to be broad and flat with a lot of surface area. Evergreen trees, on the other hand, protect their leaves by layering up with a waxy outer coating. Evergreen leaves are usually smaller, thinner or needle-like, which also protects them from the ravages of winter.
In the Lowcountry, we have a lot of beautiful live oak trees lining the banks of the salt marshes. While they are technically deciduous, live oaks grow new leaves as they lose their old one, so that the tree is never bare. In this way, it resembles an evergreen.
Leaves that fall from trees play an important role in the forest ecosystem. As they break down, fallen leaves enrich the soil. By losing all of their leaves, trees are also more readily able to disperse pollen to seeds and to fertilize the next generation.
Deciduous trees can sense the days getting shorter by the change in the amount of chlorophyll being produced by their leaves. This trigger causes the tree to stop sending vital nutrients to the leaves, which, in turn, causes the leaves to stop producing chlorophyll altogether.
Without the presence of chlorophyll, other chemicals produced in the leaves are able to show their colors. These include carotenoids, which produce yellow, orange and brown leaves, and anthocyanins, which produce red fruits, berries and leaves.
How do the leaves actually fall off a tree? Leaves have a group of cells called an abscission layer in the stem, which slowly chokes off each leaf until it dies. Through decomposition, the stem and leaf become brittle and eventually fall off the tree.
This winter, as you survey the unique landscape of the Lowcountry, take time to appreciate the humble, bare tree and its sophisticated method of surviving the cold.
By Jessie Renew, Outside Hilton Head
For more than 30 years, Outside Hilton Head has provided personalized adventures for all ages, from kayak, fishing, nature and dolphin tours to kids’ camps, history excursions, family outings and stand-up paddle boarding. To book your holiday kayak outing with Outside Hilton Head, call (843) 686-6996 or visit outsidehiltonhead.com.