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Why leaves change color
Garden Tips Newsletter - October 15, 2001

As I drove down the Natchez Trace Parkway this weekend, I enjoyed signs that fall is here -- red, yellow, and orange leaves. Fall leaf color is a result of chemical processes that take place in the tree as it prepares for winter. Leaves serve as the factories where most of the tree's food is made. This process takes place in the leaf in cells that contain chlorophyll -- chlorophyll gives the leaf its green color. Along with the green pigment found in chlorophyll, other pigments such as yellow to orange are also found in the plant but are masked by the green pigment.

In the fall, cool weather signals the trees to slow down its vital food-making processes. This causes the green chlorophyll to breakdown, allowing the other pigments (primarily yellow) to become more visible. The more vibrant reds and oranges are the result of chlorophyll breakdown, but also further chemical reactions with extra sugar that is left in the leaf. Temperature, light, and water supply all influence the degree and duration of fall leaf color. Low temperatures above freezing will enhance the leaf color in many trees.

For a more detailed explanation of why leaves change color, see http://www.msucares.com/pubs/is0818.htm.

These archived newsletters were written by Dr. Lelia Scott Kelly. Kelly is a Horticulture Specialist with the Mississippi State University Extension Service. Her office is in the North Mississippi Research & Extension Center, Verona.