Short Wave Fall foliage is still a mystery: Why do some leaves turn red?
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Nov 7, 2025 
Nell Greenfieldboyce, NPR's science correspondent, dives into the autumn mystery of why some leaves turn red. She explains how red pigments are produced in the fall, contrasting with the yellow reveal of chlorophyll breakdown. Nell discusses theories suggesting these pigments may protect leaves from damage and help trees reclaim nitrogen. Intriguingly, red leaves might even deter insects like aphids. With regional variations and ongoing research, the science of fall foliage offers fascinating insights into nature's color palette.
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A Biologist's Quest For The Perfect Red Leaf
- Biologist Nikki Hughes has a lifelong fascination with finding the 'perfect red leaf.'
- Her curiosity led her to study why some trees make red pigments in autumn.
Different Origins For Yellow And Red
- Yellow pigments are present year-round and become visible when chlorophyll breaks down in fall.
- Red pigments are synthesized anew each autumn rather than revealed.
Red Pigments Work As Leaf Sunscreen
- Red pigments act like a sunscreen, protecting leaves from excess light and free radicals.
- Plant physiologists view photo-protection as a key function of autumn red colors.