Science of Changing Leaves

— Henry Myers, Environmental Educator

Autumn is a great time of year. The mornings are cool and crisp, but the afternoons are still warm and comfortable. Apple picking is in full swing and children are getting excited about their Halloween costumes. And my favorite part, the fall foliage, a naturally occurring phenomenon when leaves change color from green to orange, red, yellow, and many other hints and hues.

Although the science behind the change in leaf color is not fully understood, here is some basic information to make your fall walk through the woods more interesting.

Three pigments are responsible for all of the bright fall leaf colors we see:

• Chlorophyll is the most important of the three pigments. It is necessary for photosynthesis, and responsible for the leaves' green color.

• Carotenoids create yellow, orange, and brown colors in leaves, fruits and vegetables. Bananas, corn, carrots, and buttercups are just some examples.

• Anthocyanins create red colors in such familiar things as cranberries, red apples, cherries, and strawberries to name a few. 

Chlorophyll and carotenoids are present in the leaf the entire growing season. During the summer chlorophyll is produced in such large quantities that it covers the yellows and oranges of the carotenoids. As the days get shorter the production of chlorophyll slows and eventually stops. This allows the yellow and orange color of the carotenoids to show. Anthocyanins on the other hand are only produced in the fall.

Check out this very cool website that has more information on leaf color change and a fall foliage tracker.