Autumn Colors
by Dr. Robert Black, Consumer Horticultural Specialist

The vivid colors of autumn are giving a final burst of glamour to the landscape before the dormant season brings on a dull hue.

Although the Florida landscape is not well known for exciting fall color, there are enough temperate region plants to provide some seasonal changes. Indian legend says that celestial hunters slew the Great Bear and that his dripping blood fell on the forest trees, gradually changing the leaves to various shades of red, orange and yellow.

However, plant scientists have unraveled the true mysteries of fall coloration. Changing temperature, day length and pigments, certain chemical substances found in nearly every living thing, all combine to bring about fall color.

Many of the pigments that contribute to the bright colors of autumn are present in leaves from the time they unfold in the spring. During spring and summer the green pigment (chlorophyll) dominates the other pigments and is the major visible color for vigorously growing plants. In fall, the production of new chlorophyll slows and is finally depleted while other pigments become more evident.

The orange, red, yellow and brown colored leaves are the expressions of carotenoid pigments. The red, blue and purple anthocyanin pigments are responsible for the red and purple colors of dogwoods and crape myrtle.

Sunny days and cool nights cause brilliant autumn colors. Cloudy days and warm nights give a more drab fall color.

When choosing plants for your landscape, select a few accent plants which provide interesting autumnal color. Unlike most flowering shrubs which display their colorful blooms for a brief period, the tree that nature paints in brilliance for the fall season usually holds its color for a month or longer, depending on weather conditions. Trees which express some seasonal foliage color change are goldenrain-tree, red swamp maple, sweet gum, crape myrtle, dogwood, tulip-tree and shumard oak. Each tree has its characteristic color, but environmental conditions varying from year to year result in no two seasons being exactly alike. By selecting the proper tree species, some seasonal changes can be incorporated in most landscapes.