Why Do Leaves Change Colors?

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What a welcome change the fall is after a very hot summer. Pretty soon the hillsides will be a panorama of color with each curve of the road bringing more colorful surprises. Even those of us who are accustomed to the changing leaves each fall cannot help but be impressed and have been known to pull off the road to take a peek at our fall foliage.

But, have you ever wondered why the leaves change? It’s beautiful and it’s a miracle but it’s also science.

Leaves are the food factories of plants. They take carbon dioxide from the air and water from the soil. A process called photosynthesis turns this carbon dioxide and water into glucose (sugar). The green color in leaves which is called chlorophyll helps this to happen.

The gradual shortening of days tells the trees that winter is coming. Trees need to rest for the winter, living off the sugar that was stored during the summer. When the leaves stop making food, photosynthesis stops, causing the green leaf color to fade. This makes it possible for you to see yellow and orange colors. These colors were in the leaf all along but were hidden by the green of the chlorophyll. In some trees like maples, the sugar is trapped in the leaves after photosynthesis is stopped. Cold weather turns this sugar to red and purple.

It is a combination of all these things that gives us our beautiful fall colors. We don’t need to think about this process to enjoy the color of fall, but sometimes it is nice to know.

trees with fall colors of yellow and red with table rock mountain in the background

Photo:  Donna Teasley