Why Leaves Change Color in Autumn

Look at the trees in autumn. Green leaves turn yellow, orange, and red. Why does this happen? The answer is chemistry and survival.

In spring and summer, trees have green leaves. The leaves make food for the tree. They use sunlight, water, and air. This process is called photosynthesis. A green chemical named chlorophyll helps make this food. Chlorophyll is very busy. It hides other colors in the leaf.

When autumn comes, days get shorter. The weather gets colder. Trees know winter is near. Winter is cold, and water is hard to find. Trees need to save energy to stay alive.

The tree stops making new food. It stops making green chlorophyll. The old chlorophyll breaks down and goes away.

Now, the green color is gone. What is left behind? Other colors!

Leaves have other chemicals inside them all year. Carotenoids make yellow and orange colors. You can see carotenoids in carrots and corn. Anthocyanins make red and purple colors. They appear in autumn when sugars get trapped in the leaf.

Without green chlorophyll, these hidden colors shine bright. The tree takes useful nutrients back into its branches. It drops the empty leaf to save water. The colorful leaves fall to the ground.

Next spring, the tree will grow new leaves and start again.

What is your favorite autumn leaf color?