What is behind the changing of leaf color?

Leaves contain raw materials, products and by-products, in chemical form and some with color. As the leaf is abandoned by the tree the green chlorophyll is broken down and recycled by the tree, leaving behind other colored chemicals. If the major chemical remaining in the abandoned leaf is red, then the leaf turns red. If it’s yellow, then the leaf turns yellow, and so on. The yearly variation in color intensity is due to varying weather conditions, which can affect the balance of chemicals and their composition in the leaves. Amounts of rainfall, sunlight, temperature, humidity and other factors effect how bright, quickly, and long the season will be each year. Color-changing leaves make for a beautiful display, but early changes in leaf-color can be a sign that your tree is stressed and is susceptible to insect and disease attack.

If the leaves on a trees seem to have gotten a jump start on fall compared with those on similar trees in the area then you may want to consult a professional technician, who can identify problems and offer solutions. Premature colors can be an indication that a tree isn’t strong enough to handle insects and disease organisms that may attack it or cold weather. Occasionally only one or two limbs of the tree will show premature fall color, which could be a sign of a disease at work, weakening only the infected limbs. The more common situation is for the entire tree to exhibit premature fall coloration, a phenomenon usually linked to root-related stress. Trees respond to these stresses by trying to minimize above ground growth.