The turning of the leaves...'tis the season!

Where do the colors come from?

Produced by photosynthesis, chlorophyll gives leaves a green color. There is also another pigment in leaves: carotenoids. Carotenoids are yellow and orange pigments. During the summer months photosynthesis produces so much chlorophyll that the leaves stay green. When Fall approaches, the days are cooler and shorter and photosynthesis stops, and no more chlorophyll is produced. With no green to be seen, the colors that have been there all along, the carotenoids, become apparent. Some trees with a lot of orange and yellow in their leaves are the sugar and black maples, the aspen of the Rockies, the hickory, and the ginkgo.

The bright red and purple colors of fall come from a pigment called anthocyanin. This pigment is also found in plants like apples, beets and grapes. Sugar, produced in the leaves, is usually transported to other parts of the tree to be used for growth. In the Fall, cool nights prevent the sugary sap from being transported out of the leaf. The sugar is trapped in the leaf. Because there is so much sugar, it reacts with certain proteins found in the cell sap to form anthocyanins. When this happens, the leaves turn the beautiful, bright colors. The red maple, the dogwood, the tupelo, and the sumac all have autumn leaves that vary from red to purple.

What makes a colorful Fall?

Fall coloration is dependent on three things: amount of sunlight, temperature and amount of water during the fall season. The temperature during the time the chlorophyll production lessens is very important. Basically dry, sunny days with cool but not freezing nighttime temperatures are the most conducive to spectacular leaf color. During the warm days, the leaf can produce a lot of sugar. During the cool nights, the sugars are trapped in the leaves and eventually produce the colors of autumn. Late springs, dry summers or a very warm spell in fall will reduce fall coloration. When frost comes early, the colorful display may not occur at a