Why do leaves change color?

Leaves are green because chlorophyll absorbs red and blue light for photosynthesis and reflects green. In autumn, shorter days and cooler temperatures signal deciduous trees to seal off leaf stems (forming an abscission layer), halting chlorophyll production. As the green fades, yellow and orange carotenoids that were always present become visible. Some species also produce red anthocyanins — possibly as a sunscreen to protect the leaf while the tree recovers remaining nutrients. Sugar maples are particularly rich in anthocyanins, producing vivid reds. The entire process takes 1–3 weeks per tree and is influenced by temperature, moisture, and genetics.