Nature connection practitioners often talk about the art of questioning as a key to developing a greater understanding of the natural world. This week my investigation started as I walked past an American Beech tree with its crinkled brown leaves dangling from otherwise barren branches. I hadn’t really investigated this phenomenon before, and as I have made a new commitment to exploring the natural world, I took this opportunity to learn something new. I quickly learned that when a tree retains its leaves it is called Marcescence. Marcescence usually occurs on deciduous tress such as beech or oak trees.
Marcescence is derived from a Latin root meaning to ‘to shrivel’1
The exact reason for the retention of leaves in the winter is not known.
“Studies have shown that the presence of these leaves may help to deter feeding by large animals like deer. Less nutrient dense brown leaves surround the buds of the tree and protect them. Since marcescent leaves can be observed most commonly in juvenile trees, it is often thought that the process does offer growth advantages. Smaller trees often receive less sunlight than their taller counterparts. Slowing the process of leaf loss may be beneficial in maximizing growth before winter temperatures arrive.
Other reasons which trees retain leaves suggest that dropping the leaves later in the winter or early spring helps to ensure that the trees receive adequate nutrients. This seems especially true in cases where the trees are grown in poor soil conditions.2
A contributing factor in marcescence is the development of the abscission layer. This layer of cells develops at the base of the leaf stem. The abscission layer is thought to protect the trees during the winter months. (More information about the abscission layer in a future post.) I did read somewhere that an underdeveloped abscission layer could result in the retention of dead leaves in the winter.
There is much more to study here about the life cycle of trees and how they adapt to the changing environment. After my initial inquiry into the reason why a Beech tree retained its leaves in the winter, I developed several more questions that require investigation.
- How does a tree develop an abscission layer and what is its main function?
- Why don’t a majority of evergreen trees drop their needles?
- Why does the Tamarack tree, a type of evergreen, drop its needles?
The questions that are developed as a result of observing the natural world are endless. Noticing the brown leaves on a Beech tree in the winter is just the beginning of long journey into nature connection.
What questions have the changing of the season brought up for you?