Earth & Sky

Kids: A reason for the seasonal burst of color?

In the fall, the leaves of some trees turn yellow, orange or red. The bright colors are wonderful to behold. But does this color change have a purpose?

For much of the year, green leaves help convert sunlight into food. In the fall, trees break down the green pigments and nutrients stored in the leaves. As the leaves of the tree begin to change, nutrients are shuttled into the roots for reuse in the spring.

Bill Hoch, a plant physiologist at the University of Wisconsin, suspected that some trees produce red pigments as a kind of sunscreen, protecting leaves from sunlight while the tree stores nutrients.

And what about tree leaves that turn yellow and orange?

Yellow and orange pigments – called carotenoids – are always in tree leaves, but for most of the year, they’re masked by green pigments that help convert sunlight into food. In the fall, trees break down the green pigments and nutrients stored in the leaves. The nutrients are then shuttled into the roots for reuse in the spring. This process reveals the yellow pigments.