Events & Information

What causes the colors?

Leaf color comes from pigments. Pigments are natural substances produced by leaf cells. The three pigments that color leaves are:

• chlorophyll (green)
• carotenoid (yellow, orange, and brown)
• anthocyanins (red)

Fall color is controlled by both the plant's genetic factors and the environment. Carotene and xanthophyll are yellow pigments produced in foliage all year; along with chlorophyll, the green pigment. In autumn when short days and cool temperatures slow down the production of chlorophyll, the remaining chlorophyll breaks down and disappears. Then the yellow pigments that have been masked by chlorophyll show up.

Some plants produce anthocyanins (red and purple pigments) that may mask the yellow pigments: maples, dogwood, black tupelo, oaks and winged euonymous brighten up with with red and purple colors.

Anthocyanin production increases with increased sugars in the leaves. A fall season with sunny days and cool nights increases sugar content of the leaves and makes fall reds brighter. This also explains the two-tone effect on green ash which exhibits yellow on leaves inside the tree and purple on the outside leaves where they are exposed to sunlight.

The tans and browns of oaks are caused by tannins which accumulate as the chlorophyll disappears.

Fall color starts in September with poison ivy and sumac and ends in November with the larches and weeping willows. Frost and freezing temperatures will stop the coloration process and blacken the leaves.