Autumn leaf color

Published: Friday, November 22, 2013 at 11:19 AM.

We may not see the incredible burst of vivid fall leaf color our northern neighbors enjoy each year, but we do have enough temperate region plants in our area to give us some seasonal changes in foliage hues.  In this article we’ll give you some scientific (facts) on why some of the leaves of some trees and shrubs change color as the weather cools.  My information was provided by Emeritus Extension Specialist Dr. Robert Black, of the University of Florida’s Institute of Food and Agricultural Science.

The brilliant display of autumn leaves is brought on by a combination of things; falling temperatures, shorter days, and certain chemical substances, called pigments, found in leaf tissues.

Some of the pigments that give autumn leaves their bright colors are actually present in the leaves as soon as they unfold in the spring.  But during spring and summer, when the plants are growing vigorously, green-colored materials call chlorophyll dominates the other leaf pigments.

Chlorophyll plays an important role in process call photosynthesis, the process by which plants capture energy from sunlight and manufacture food.

Chlorophyll is produced in the leaves of most plants during their active growing season.  But, in the fall, as plants get ready for dormancy, the production of new chlorophyll slows down.  Finally, it stops altogether, and there’s no chlorophyll left in the leaves.  When this happens the other leaf pigments those we mentioned earlier take over and you see the bright cool-season colors.

Pigments called carotenoids (care-oh-the-noids) make the leaves turn orange, red, yellow, and brown.  Other pigments, call anthocyanin’s (an-tho-cy-ah-nins), are developed because of the changing weather conditions.  Bright, clear autumn days and cooler temperature produce shades of red and purple in the leaves.  Still another group of pigments, call anthoxanthins (an-tho-zan-thins), cause yellow coloring in some foliage.

Even though Florida’s landscape is not famous for brilliant fall colors, there are plants in some areas that do change color with the seasons.  It’s a good idea to include a few of these in home plantings. Unlike most of the flowering shrubs that turn color in the fall will usually retain their varied hues for a month or more, depending on the weather.

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