Why do leaves change color in autumn?

Leaves change color in autumn due to a combination of biological and chemical processes triggered by changes in daylight and temperature. During the growing season, leaves are green because of chlorophyll, the pigment that helps plants capture sunlight for photosynthesis. As days shorten and temperatures drop in autumn, chlorophyll production slows down and eventually stops. Without fresh chlorophyll, the green color fades away. As the green pigment disappears, other pigments that were present in the leaf all along become visible. Carotenoids, responsible for yellow and orange hues, are always present but usually masked by chlorophyll. Anthocyanins, which produce red and purple colors, are produced in the leaf during autumn in response to sugars trapped in the leaf as chlorophyll breaks down. The combination of these pigments results in the vibrant fall foliage colors of yellow, orange, and red. Ultimately, this color change is part of the tree’s preparation for winter. The tree reabsorbs nutrients from the leaves and forms a protective layer at the base of each leaf stem, causing the leaves to eventually fall off. This process helps the tree conserve water and energy during the cold months when it cannot maintain its leaves effectively.