Intro

Scientists know why leaves turn yellow in the fall: Chlorophyll breaks down, revealing the yellow pigment that was there all along. But red? Red is a different story altogether. Leaves have to make a new pigment to turn red. Why would a dying leaf do that? Scientists don’t really know. NPR science correspondent Nell Greenfieldboyce reports on the leading hypotheses out there.

Read more of Nell's reporting on this topic. 

Interested in more seasonal science? Email us your ideas at shortwave@npr.org.

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