Why do leaves turn color in fall?

Plants fascinate us. From tiny seeds to towering trees, we gardeners not only want to care for them, we want to know what makes them tick. One of natures most beautiful transformations is the vibrant colors of fall foliage. But what makes the leaves change color?

Plants fascinate us. From tiny seeds to towering trees, we gardeners not only want to care for them, we want to know what makes them tick. One of natures most beautiful transformations is the vibrant colors of fall foliage. But what makes the leaves change color?

There are three types of pigments that contribute to the development of fall color:

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• Chlorophyll gives leaves their green color. This substance is necessary for photosynthesis, the chemical reaction that allows plants to use sunlight to create their own food.

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• Carotenoids produce yellow, orange, and brown colors in corn, carrots, daffodils, rutabagas, buttercups and bananas.

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• Anthocyanins give reddish color to cranberries, apples, concord grapes, blueberries, cherries, strawberries and plums.

Chlorophyll and carotenoids are present in leaf cells throughout the growing season, while anthocyanins are produced in the fall in response to bright light and storage of excess plant sugars within leaf cells.

During the growing season, chlorophyll is produced continuously and gives leaves their green appearance. As days become shorter and nights get longer, chlorophyll production slows down to a stop and eventually all the remaining chlorophyll is destroyed. The carotenoids and anthocyanins that are already present in leaves become visible and show their colors.

Different tree varieties experience different leaf color changes due to varying levels of carotenoids and anthocyanins among the species. Oaks generally turn orange and red, aspen and poplar turn yellow, and maples turn brilliant shades of red to gold.

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