Bill Starr: The leaves are coloring

Published 3:12 pm Monday, November 9, 2015

The neighborhood where I live is blessed to have many hardwoods that hopefully will exhibit some beautiful colors this fall. It seems trees are a little slower this year changing colors; maybe due to the fact we have had some strange weather. For those of you old enough to remember, the band the Eagles had a song “Peaceful Easy Feeling.” I am sure that song was written about enjoying the bounty of fall colors that should be apparent very soon.
This show of fall leaf color is an amazing thing. Think about it: A green leaf will turn to one of many vibrant colors before it drops to the ground. Why does it do that? Lots of animals and plants put on a color show to attract the opposite sex or, in the case of plants, a pollinator. But why do the leaves put on that color? Is there a purpose? There doesn’t seem to be, except maybe to provide beauty to us lowly humans.
The process of the color change is one that bears some explanation. You see, the leaf doesn’t turn red or yellow or brown due to some chemical appearing in the leaf. It actually makes the change because of a chemical disappearing from the leaf.
A leaf contains chlorophyll. This green pigment captures light and converts it to food for the plant, and for us. The green color is actually covering up the reds and oranges and yellows that we see in the fall, when the weather cools and chlorophyll is produced in smaller amounts and finally, not produced at all.
In fact, if anything affects the manufacture of chlorophyll in the plant leaf, then these colors we associate with fall may be seen in the summer. You may have seen a limb of your tree turn to red or yellow while the rest of the tree remains green. Something has interfered with the chlorophyll and the “true” color of the leaf comes out.
The true color? Well, yes. Leaves with high sugar content produce anthocyanins. These pigments produce the reds, purples, blues and pinks we see. The pigment is dissolved in the sap of the tree. If the sap is acidic the pigment shows red. If the sap is basic then the pigment is blue. As the weather cools the sap becomes more acidic in many trees and the red colors appear.
Xythophylls and carotenoids are also in leaves. These pigments produce the yellow and orange color. They react with the tannins in oak to produce the yellow-brown color common in oaks in the fall.
When the anthocyanins and carotenoids combine, deep oranges, bright reds and bronze colors develop. If you think about all the possible combinations and concentrations of these pigments, you can imagine hundreds of different shades of color in the fall leaves.
So now you know more than you ever wanted about fall color. Hope I haven’t ruined it for you.  Get out there and enjoy one of nature’s most beautiful displays of color; It won’t last long, and then the raking begins!

Bill Starr is Sumter County Extension agent/coordinator, University of Georgia Cooperative Extension Service. Contact him at 229-924-4476.