• Editor’s Note: This article was written by Valerie Blaine, nature programs manager for the Forest Preserve of Kane County. She addresses one of the questions I’ve been asking myself every year: Why the heck do some trees keep their leaves well into the winter?
  

In the wake of yesterday’s wind storm, it’s amazing that there are any leaves left on the trees. But if you look around, you’ll see that many trees are holding on to their leaves. Some trees retain their leaves through thick and thin, as if unable to let go of the fading memories of summer.

Why do some trees keep their leaves all winter, while others drop them all in autumn? The answer lies in the physiology of the tree and the fickleness of Mother Nature.

In fall, the tree gets cues from the environment that tell it the season is changing. More specifically, the shortening daylight and cold night temperatures induce changes in the leaves. Some of these changes include the breakdown of chlorophyll — the green pigment — which unveils spectacular colors underneath.

Another change is the formation of cells that separate the leaf from the branch. This is called the abscission layer. Sometimes, the formation of the abscission layer is interrupted, the separation incomplete, and the leaf remains stuck to the tree all winter. In spring, new buds push the old leaves away.

The fancy name for this (should you want to pull out an impressive word once in a while) is marcescence. Young trees are more often marcescent than old, and oaks more so than other hardwood trees. Beech, ironwood and witch-hazel also have marcescent tendencies.

There’s a rugged beauty in these tenacious trees.  A lone oak at the edge of the prairie, clothed in leaves amidst a swirling white blizzard, is nature’s work of art, and the sound of rattling leaves on a cold, windy day is winter’s music. There’s poetry in marcescense, too, which I will leave to Robert Frost.

A Boundless Moment

About the Kane County Forest Preserve District

The Forest Preserve District of Kane County acquires, holds and maintains land to preserve natural and historic resources, habitats, flora and fauna. The district restores, restocks, protects and preserves open space for the education, recreation and pleasure of Kane County citizens. For more information, visit the district’s website or find them on social media via Facebook, Twitter or Instagram. Also, sign up for the quarterly TreeLine Newsletter.