Coast Gardener
The Leaves They Are a Changin’
Coast Gardener Newspaper and Web Column - November 17, 2008
Fall has always been one of my favorite times of the year. Waking up in the morning and feeling that chill in the air, even 70 degrees is chilly after a hot, humid summer in southern Mississippi. The Gulf Coast has festivals that seem to happen every weekend: Feast of Flavors, Cruisin’ the Coast, the Peter Anderson Festival, etc.
The best part always has been watching the trees change color. Red, yellow, or orange and every color in between, fall is truly the season when mother nature shows off her color palette.
But where do the fall colors come from?
The answer is found when we take a very close look at the structure of leaves. The primary function of leaves is to absorb sunlight to allow the plant to perform the miracle of transforming light energy into chemical energy. In other words, it creates sugars that the plant uses for growth. This process of light absorption is called photosynthesis.
But where do the fall colors come from?
Sunlight is made up of light at different wavelengths and each wavelength is a different color. We have all seen these different wavelengths and colors of light before. Think of a rainbow. Leaves have many pigments that absorb these different wavelengths of light. The primary pigment in a leaf is chlorophyll which absorbs light in the blue and red range. Leaves are green because chlorophyll actually reflects the green portion of sunlight. This masks the other pigments including carotenoids (reds, orange and yellows) and anthocyanins (reds, blues, and purples).
But where do the fall colors come from?
During the fall there are strong environmental cues occurring. The day length and night time temperatures are decreasing. Trees can sense these changes and start recycling nutrients in the leaves and move them to the roots for use next year. Chlorophyll is broken down very quickly in this process. Once the chlorophyll is gone the other pigments become apparent by reflecting the other wavelengths (colors) of sunlight.
Now our fall colors are not as spectacular as the mountains of North Carolina or New England, but are beautiful all the same. Enjoy the red/oranges of the maples, dark purples of black gum, reds and purples of dogwood and crape myrtle.
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Written by Dr. Gary R. Bachman, Assistant Extension Professor of Horticulture, Coastal Research & Extension Center.