October 31, 2018

Red Oak Fall Foliage

Closing out October aka Oaktober with an explanation of the sources of fall colors.


The dark green leaf is a summer leaf, colored by chlorophyll. The yellow leaf is colored by a class of pigments called carotenoids. This pigment family is present in the leaf during the spring and summer but only surfaces with the decline in chlorophyll in the fall. Tannins are responsible for brown leaf color. Tannins are present in the tree throughout the year, too, but chlorophyll and carotenoids mask their expression. Carotenoids are also responsible for orange fall colors. Anthocyanins are the source of red and purple leaves in the fall. Unlike carotenoids and tannins which are present in the leaf during the growing season, anthocyanins are produced when sugar availability increases in the fall. Why do leaves make anthocyanins in the fall? Research suggests that red leaf color protects senescing leaves.

What's the state of fall color in your area? Let me know in the comments.

A version of this post first appeared here.

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