Leaves contain yellow and red pigments all summer, but only as the chlorophyll molecules break down do those colors become visible. Illustration by Chris Philpot.

Fall Fade

As days shorten in the fall and temperatures drop, trees quit making food through their leaves. The chlorophyll, which absorbs light to make that food and gives leaves their green color, fades out.  

Time to shine

Leaves contain yellow and red pigments all summer, but only as the chlorophyll molecules break down do those colors become visible. Various mixes of chemicals, called anthocyanins, determine which color a given species will produce. 

Glow up

How bright a tree’s leaves turn depends on recent weather and how much summer rainfall a grove has received. A wetter summer followed by fair days makes for the best pop.