Why the Leaves Change Color in the Fall
Wednesday October 19, 2005
Ever stop to wonder what's going on around you when the weather starts to turn a little colder? Read on...
We have all been asked why the sky is blue, where the moon goes in the daytime, and why leaves change color in the fall. These questions typically come from an inquisitive child in search of solving the mysteries of the earth. We can usually get away with a response that will satisfy the child, but does not offer much of an explanation. Most of us are pleased to have our inquisitive young friends move on to a game of hide-n-seek without explaining these mysteries, only to ask ourselves the same questions later and seek an explanation. The truth is that even scientists do not fully understand the varying change of leaf color in deciduous trees. However, leaf pigments, length of night, tree species and overall weather conditions play a part in the color transformations of fall forests. All summer deciduous trees are lush and green because they are full of the pigment chlorophyll. Chlorophyll enables a plant to capture the sunlight it needs for photosynthesis, the process of manufacturing food. There is such a great amount of chlorophyll present in leaves through the summer that the green color masks other pigments present in the leaf. As days begin to grow shorter in the fall, chlorophyll production slows and eventually stops, allowing other pigments to become visible. The other pigments present in deciduous tree leaves are carotenoids, producing yellow, orange, and brown colors and anthocyanins, producing red and purple colors. Certain tree species characteristically turn different colors based on the presence of carotenoids and anthocyanins. In our eastern Tennessee forests and yards you may enjoy the golden bronze leaves of hickories, scarlet red maple leaves, purplish dogwoods and oaks ranging from red to brown or even russet. Of course, if you look forward to enjoying the fall foliage display each fall, you know it is a guessing game of when to plan a trip to your favorite forest. Temperature and moisture influence fall foliage, therefore, no two falls are ever the same. Warm, sunny days and cool nights bring spectacular color displays of scarlet, purple and crimson leaves. Bright sunlight in early fall increases food production in plants. The food or sugar is trapped in the leaves encouraging the production of anthocyanins and turning the leaves brilliant shades of red. Carotenoids are always present in leaves so the yellow and gold colors are fairly consistent from year to year. However, even the consistent change from green to golden can be delayed by a late spring or summer drought. Warm falls may be enjoyable but can lower leaf color intensity we all enjoy. Taking all of these things into consideration, we can normally enjoy the fall colors beginning in late September through October. So, join your favorite inquiring minds, young or old, in the forest this fall and give them an answer to the question, “why do leaves change colors in the fall?” Be sure to visit the Discovery Trails at the Ijams Home Site and Tharp Trace at Meade’s Quarry for what we hope will be a spectacular fall.
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