Gardening Tips and Highlights

Why leaves change color in the fall?

Even if you live in the most tropical of climates, where summer is your only season, you still can’t help but marvel at the splendor of a brightly colored autumn vista. So, what’s behind this annual event? Why do leaves change color every fall and why are some years more vivid in color than others?  

To understand what’s involved each fall in the transformation from a sea of cool green to a kaleidoscope of red, orange, yellow and every shade in between, it is helpful to know two important points. The timing of leaf color change is primarily affected by the calendar and the intensity is a product of three main factors, color pigments, length of night and weather. 

First are the pigments. There are three most responsible for leaf color. Most of us are familiar with the first, chlorophyll. You know it as having something to do with providing the basic green color found in leaves and grass. It’s required for photosynthesis, the chemical process that allows plants of all sizes to use sunlight to produce food.  

During the warmer months when plants are actively growing, the chlorophyll pigments dominates the color we see in leaves. However, another pigment is also present at this time, carotenoids, which produces the yellows, oranges and browns, but because chlorophyll is so dominating as a pigment, it is not until fall, when the photosynthesis process ceases and all chlorophyll is depleted, eliminating the green color completely from certain leaves and allowing the carotenoid pigments to take center stage. A third pigment, anthocyanins are not present in leaves until autumn.

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