The main function of the leaves on trees and shrubs is to produce food for the plants. Photosynthesis is the process through which green plants make carbohydrates by combining energy from the sun, carbon dioxide and water. This photosynthetic process is also responsible for the oxygen in the earth’s atmosphere.
In the fall, leaves on deciduous trees and shrubs stop making chlorophyll. The old chlorophyll begins to break down slowly in the leaves. As they lose their green color, other color pigments in the leaves become visible.
The two general groups of colored pigments in leaves are anthocyanins and carotenes. Anthocyanins are the blue, red and purple pigments formed in the cell sap. Carotenes are the orange-yellow pigments. Some plants also contain tannin which gives a russet and brown color.
Trees’ development of fall colors is a slow process that is destroyed by early and hard frosts.
Red maple, sugar maple, sweet gum and pin oak are deciduous trees that turn a beautiful red color in the fall.
Double file viburnum, “Arnold Promise,” witch hazel and dwarf winged euonymus are deciduous shrubs that give a wonderful scarlet color in autumn.
Deciduous trees that display the brilliant yellow colors are Norway maple, birch, beech, green ash, willow oak and redbud.
Deciduous shrubs that exhibit a golden yellow color are Chinese witch hazel, common witch hazel, vernal witch hazel and redvein enkianthus.
Next time you are outdoors and notice how beautiful the trees are in their fall colors, you’ll know how this process transpires.
Delaware Cooperative Extension-Delaware State University