Why Do Leaves Change Color in Fall?
Leaves change color because they stop producing green chlorophyll as days shorten. This reveals yellow and orange pigments (carotenoids) that were always present but masked by green. Red and purple colors (anthocyanins) are actively produced in fall. Trees reabsorb valuable nutrients from leaves before dropping them for winter.
Key Takeaways
- Chlorophyll is the green pigment that captures sunlight for photosynthesis.
- Different tree species have different dominant fall colors based on their pigment chemistry.
- Weather affects intensity - dry, sunny days with cool nights produce the brightest colors.
Explanation
Chlorophyll is the green pigment that captures sunlight for photosynthesis. It is constantly produced during summer, masking other colors. As daylight decreases in fall, trees begin shutting down chlorophyll production. Without new chlorophyll, the green fades, revealing underlying pigments.
Yellow and orange colors come from carotenoids - pigments present in leaves year-round. They help with photosynthesis and protect against sun damage. Once chlorophyll fades, you finally see these colors. Red and purple come from anthocyanins, which many trees produce specifically in fall, possibly as sunscreen while reabsorbing nutrients.
This process is part of how deciduous trees prepare for winter. They cannot sustain leaves during cold months (frozen water cannot flow through). Before dropping leaves, they break down chlorophyll and reabsorb the nitrogen and other valuable components, storing them for spring growth.
Things to Know
- Different tree species have different dominant fall colors based on their pigment chemistry.
- Weather affects intensity - dry, sunny days with cool nights produce the brightest colors.
- Climate change is affecting fall color timing and intensity in many regions.