The brilliant colors of fall entice each one of us to get outside, go for a walk, and enjoy the beauty around us, but when we begin to see those colors fall, we know the winter cold is upon us. However, what if those leaves have not yet fallen by February?
Abnormal weather patterns during the end of fall and early winter can cause trees to adaption to be stifled. For instance, early winter storms, freezes, or cold weather for the time can prevent winter leaf drop; as well as the alternative of a warmer weather pattern continuing through early winter.
Why can some trees not lose their leaves?
Maples, birch, willow, oak, hickory, dogwood, and redbud are all deciduous trees that are known for losing their leaves during the winter. In fact, the end of the summer usually warrants a color change of beautiful yellow, orange, purple and red with longer-lasting leaf drops; compared to some deciduous leaves that will turn brown and drop as quickly as the color transition occurred.
When experiencing a frost, maple winter leaves will turn brown and shrivel up around the edges, but the leaves will hold on until they are meant to fall. With this being said, maples should be able to bud in the spring with ease.
However, when redbud winter leaves experience frost damage the leaves will turn brown, shrivel up, and fall. In spring, the tree, in a healthy state will bounce back and bloom a full canopy.
So, you’re wondering why your tree still has leaves? Well, with few explanations, the weather is the primary cause of your tree still holding onto its leaves. In Wisconsin, we are having an abnormally warm winter, believe it or not. Very few winter storms have hit Wisconsin resulting in trees with leaves in winter. Marcescence is a term arborists use to describe persistent dead plant organs that normally shed at the end of fall. Specifically, oaks and beeches are known as being particularly persistent trees.
What happens when a tree doesn’t lose its leaves?
Understanding why winter leaves remain on trees requires one to understand why leaves lose their leaves in the first place.
Trees that lose their leaves in the winter go through a process of cutting off chlorophyll production, resulting in the exposure of leaf color. For the winter leaves to drop, the branches of the tree begin producing abscission cells. The cell’s primary job is to cut off these dead plant organs (the leaves) and heal the section where the stem and branch couple.
Trees with leaves remaining in winter can be a result of the temperature dropping in early fall. This temperature drop causes leaves to be killed instantly – changing the color from green to brown. When this immediate change happens, abscission cells cannot form within the branches, resulting in leaves holding on throughout winter. Eventually, the winter leaves will fall, and the tree will begin its normal spring blooming.
We started out our Wisconsin winter with an abnormally warm climate. A key driving force of winter leaves dropping, is the temperature dropping. This temperature drop is an indicator to trees to begin their dormant winter state. However, with temperatures remaining warm this winter, trees abscission cells are never formed. Without the cells being formed, the winter leaves may continue their duration on the branches, until they are forced off from wind or other factors.
Trees with leaves in winter can also be a result of a tree so focused on growing, that it doesn’t prepare for winter. Untimely use of excessive nitrogen fertilizer used to assist in the growth of the tree can cause this delayed dormancy.
If your tree still is holding its leaves at this time of the winter or has only recently begun to drop its leaves, don’t be alarmed. When spring arises and your trees are still awaiting their bloom, call a Wachtel Tree Science Certified Arborist for a consult on your trees. Remember, trees with leaves in winter are not something to be wary of.