Sweetgum leaves turn many colors in the fall, from yellow to purple.
The amount of daylight (photoperiodism) prompts the color changes in leaves, not cooler temperatures. As days get shorter, trees use less chlorophyll. All that green pigment starts to degrade, revealing the other leaf pigments.
- Trees with leaves that always turn yellow include tulip poplar, birch, hickory, and redbud.
- Some trees have leaves with high amounts of tannins in them (like oaks). These leaves may turn brown in fall.
- Yellow and orange colors come from carotenoid pigments; red color comes from anthocyanin pigments. The combination of both pigments produces the deep red, oranges, and gold colors of fall leaves.
