Photo © 2005 Jim Jung and licensors. All rights reserved.

Fall Color

Here's a question I'm asked occasionally: why do the leaves of our trees change color just before leaf fall?

Well, the short answer is that they only cease being green. The trees are withdrawing all the nutrients and useful compounds from their leaves in preparation for winter and the first thing they remove is the chlorophyll - the compound that gives them their green pigment. Whatever pigments are left is what we perceive as fall color. These leftover pigments - the reds, yellows, oranges and purples - are present throughout the growing season but are never seen because they're swamped by the huge amount of chlorophyll the trees pack their leaves with during the growing season.

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