The science behind autumn's colorful leaves

By Peggy Weng, 2025

Published 10/29/22

Now that the fall colors are among us, some may wonder, how do leaves of plants change colors? Aside from admiring the wide assortment of heartwarming colors—from a dark cranberry red to a sunny yellow, I think that we should take the time to appreciate the science behind this phenomenon.

Most of us have probably heard the term ‘chlorophyll’ before, in a biology class. It is the chemical that gives leaves a green color. Chlorophyll is also responsible for taking in sunlight that would be converted to glucose through photosynthesis. During the summer months, abundant sunlight causes chlorophyll to become the dominant chemical that overshadows other shades. In the fall, the weather becomes cool and dry and the sunlight weakens. With less sunlight, the leaves are not able to produce as much chlorophyll. When chlorophyll production halts soon after, the green color gives ground to carotenoids and anthocyanins which are orange, yellow, or red pigments. To conserve water and energy, leaves detach from the tree and fall!