Lesson On Fall Leaves

We are quickly approaching the fall season and there is much to do: Bring in the harvest from our gardens, enjoy all the festivals and the football! Amid the joys of fall come the task of yard clean up. WHY do trees have to shed their foliage and litter our yards, bringing muscle-aching work for us? Let me share some insights.

Autumn in the Ohio Valley is a beautiful time of year. It is a time when blue skies, sunny days and cool nights gradually paint the wooded hills and tree-filled valleys a hundred hues of yellow, orange and red. It is a time when evergreen pines and cedars provide a sober backdrop for the vibrant reds and yellows of their deciduous cousins (trees that shed their leaves).

The whole process whereby trees lose their leaves is practical as well as beautiful. By losing their leaves, trees conserve energy during the Ohio Valley’s harsh winters. They also rid themselves of toxic wastes that build up in the leaves during the summer.

You may wonder how this colorful transformation takes place. Autumn colors are part of the process by which trees prepare for winter. As the days get shorter in the autumn, a tree’s internal clock alerts the tree to begin cutting off the water and the nutrient supply to the leaves. When this happens, each leaf constructs a separation layer at the base of the stalk. This layer blocks off any circulation from the leaf to the rest of the tree and causes the leaf to eventually fall off the tree.

While this whole process is happening, carotenoid pigments begin giving leaves their yellow or orange color. I find it interesting that these pigments are usually present throughout the summer, but they go unnoticed because of the predominant green chlorophyll in the leaves. But we see a lot of red, too; where does that come from? The red color comes mainly from anthocyanin, a pigment that the leaves do not produce until autumn. During the autumn, chlorophyll breaks down the yellow, and the red pigment takes center stage. When there is no chlorophyll left, a poplar leaf turns bright yellow, but a maple leaf takes on a brilliant red color. The sugar in the maple tree has to do with this transformation.

What happens to all these leaves that fall to the ground? Thanks to insects, fungi, worms and other soil animals, all this organic material is soon converted into humus, a vital ingredient of fertile soil. So after providing us with a dazzling spectacle, the fallen leaves also provide fertilizer for new growth in the spring. Can you imagine a more attractive recycling process?

So instead of back-breaking raking, shred the leaves up with your lawn mower. An inch or two of chopped leaves on your grass will add needed nutrients to your soil. Of course, the earthworms also will appreciate the meal. Shredded leaves are also great for your garden and compost, giving your soil the fertilizing it needs.

But, before you have to think about taking care of the leaves in your yard, take time to enjoy their beauty. Plan to take a walk or bicycle ride in your local park or drive to the hills or mountains and drink in nature’s artwork of the fall leaves as the trees do their annual housekeeping to get ready for the close of another growing season.

Kathy Dillon is the office administrator at the consulting firm of Hays Landscape Architecture Studio in St. Clairsville.