Why Leaves Change Color in the Fall

Written By: Sydney G

Have you ever wondered why the green leaves of summer turn into bright yellows, oranges, and reds in the fall? It’s like nature paints a beautiful picture every year, but there’s some fascinating science behind this transformation.

Leaves get their green color from a special pigment called chlorophyll. This pigment is what plants use to make food through a process called photosynthesis. By capturing sunlight, chlorophyll helps plants turn water and carbon dioxide into the sugars they need to grow. During the summer, chlorophyll works so hard that it hides all the other colors in the leaves.

When fall comes, the days get shorter, and there’s less sunlight. The trees start to prepare for winter by slowing down photosynthesis. Since they won’t need their leaves during the cold months, the trees stop making chlorophyll, and the green color fades away. That’s when the other pigments in the leaves get their chance to shine.

The yellow and orange colors come from pigments called carotenoids, which have been in the leaves all along but were hidden by the green chlorophyll. The red and purple colors are made by anthocyanins, which the leaves produce in the fall. Scientists think these red pigments might help protect the leaves while the tree reabsorbs important nutrients, like nitrogen, before letting the leaves drop.

You can see this science in action with a simple experiment. Collect leaves of different colors and place them in rubbing alcohol to soak overnight. The pigments will dissolve into the liquid, showing you the colors that were inside the leaves. It’s a great way to explore the chemistry of fall!

The next time you see a tree with vibrant autumn colors, you’ll know it’s more than just a seasonal change—it’s the result of a clever plan by the tree to save energy and prepare for winter. The beauty of fall is a perfect example of how amazing biology can be!

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Works Cited:

“Why Leaves Change Color.” ESF, www.esf.edu/eis/eis-leaves-color-change.php#:~:text=But%20in%20the%20fall%2C%20because,part%20of%20their%20fall%20splendor. Accessed 22 Jan. 2025.