Why does a green leaf turn yellow or red?

Pigments are substances that give leaves their colors. Green chlorophyll helps plants capture sunlight for photosynthesis, the process they use to make food.

Shorter days help signal autumn preparations. As chlorophyll breaks down and is not replaced, yellow and orange pigments become visible. Red pigments called anthocyanins can be produced during autumn.

Tree species and weather affect the display. An early hard frost can shorten it. Watch the same tree and note dates and colors: not every tree changes on the same schedule.