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Why Do Leaves Change Color?

Each fall we are treated to a spectacular display of colors by Mother Nature.  With fall comes less sun and cooler temperatures allowing the green leaves of summer to change color.  Ever wondered what processes lead to this yearly occurrence?  Well, read on about the wonders of fall and how you can find out where the best viewing will be.

During the spring and summer a food-making process takes place in the leaf cells containing chlorophyll.  This gives the leaf its green color.  The chlorophyll absorbs energy from sunlight and uses it in transforming carbon dioxide and water to carbohydrates, such as sugars and starch.

In the fall, the decrease in the intensity of sunlight and the cooler temperatures cause the leaves to stop their food-making process.  The chlorophyll breaks down causing the green color to disappear, and the yellowish colors or pigments already in the leaf become visible.  The fall foliage of some trees are mostly yellow colors including aspen, cottonwood, birch, hickory, white ash, American elm, beech, yellow poplar, and willow.

From the sugars trapped in the leaves a red pigment is often formed.  Many areas east of the Mississippi River experience brilliant shades of red.  Trees with red or scarlet leaves in fall are red and silver maple, dogwoods, sweetgum, red oak, black oak, scarlet oak, sumac, and sassafras.

Fall weather conditions favoring the most brilliant colors are warm sunny days and cool, but not freezing, nights.  A few hard frosts can cause the leaves to wither more quickly and drop to the ground.  The degree of color may also vary from tree to tree.  Leaves directly exposed to the sun may turn red, while those on the shady side of the same tree or other trees may be yellow.  When there is much warm, cloudy, and rainy weather in the fall the leaves may have less red coloration.

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