Fall Colors Are Here

Cassie Homan, Horticulture Agent

Part of the allure of fall foliage is the immense and beautiful color variation. There are trees that turn red, purple, yellow, orange and brown. It is such a joy to take a walk on a breezy fall day and look at all the trees changing from vibrant green to intense warm colors.

Why do leaves turn color? Specific plant pigments determine individual colors. Foliage derives its normal green color from chlorophyll, the substance that captures the energy of the sun. Other pigments are responsible for producing fall colors. Reds and purples are caused by anthocyanins, yellows by xanthophylls, and oranges by a combination of carotenes and xanthophylls. Browns are the result of tannins present in the leaf. Most of these substances are present throughout the growing season but are masked by the green color produced by chlorophyll. Anthocyanins are the exception and are produced after the chlorophyll is destroyed in the fall.

If you have been to New England in the fall, or have seen pictures, you have probably wondered why trees in Kansas usually do not color as well. This difference is partly because of the tree species prevalent in New England. Certain oaks and maples naturally produce good color. Another difference is weather patterns; temperatures can greatly effect coloration.   

Warm, sunny days and cool nights are ideal for good color. The sunny days encourage photosynthesis and, thus, sugar accumulation in the leaves. As fall progresses, each leaf develops an abscission layer at the base of the leaf stem. This layer prevents sugars from being transported down the trunk to the roots for storage. This high sugar content in the leaves produces more intense colors. Cloudy days and warm nights prevent some of the sugar accumulation in the leaves and results in less vibrant colors.

Weather during other parts of the growing season also can have an effect. Heavy rains in the early spring or hot, dry weather during the summer can both have a deleterious effect on fall color. The length of time a tree maintains fall color also depends on weather. Reds, yellows and oranges are short-lived when trees undergo frosts and freezes.

Take some time this fall to enjoy all the beautiful colors, they won’t last for long.  If you would like more details about the trees in your landscape contact Cassie Homan, Post Rock District Horticulture Agent, at (785)738-3597 or by email at choman@ksu.edu