Why do leaves change color in the Fall?
Most of the spectacular colors of Fall have actually been in the leaves all summer, however they were covered up by the dominant green of the chlorophyl. As weather cools, and shorter days settle in, the chlorophyll begins to break down, revealing new and varied color pigments. The brightest colors are seen when late summer is dry, and fall has bright sunny days and cool nights.
Green - Chlorophyl
Chlorophyll is responsible for helping trees and plants turn sunlight into food. For most months, it is the dominant color seen in most leaves until it fades away. As many trees shut down their food production, they turn to stored sugars to survive the winter.
Red - Anthocyanin
Unlike other leaf colors that always exist in the leaf, anthocyanins are produced as the chlorophyl is broken down. The anthocyanins are often seen in leaves named for their autumn splash of red including Red Maples, Scarlet Oaks, and Red Sumacs.
Orange - Carotene
Sugar maples may be one of the best examples of carotene in action. Their bright signature orange fills many hills and country roads throughout the northern US. Sassafras leaves also turn a slightly more muted orange. As its name implies, carotenes are also the chemical responsible for giving carrots their unique coloring.
Yellow - Xanthophyll
Xanthophyll can be seen throughout the fall in trees including beeches, ashes, birches, aspens, and some oaks. It also contributes its bright yellow color to autumn squash and corn.