Have you ever noticed that after leaves change from bright green to beautiful shades of yellow, orange, red and brown, they eventually fall to the ground? This is how trees prepare for winter!

Why do leaves change color in autumn?

During the spring and summer months, leaves are making lots of chlorophyll, the green pigment in leaves. Chlorophyll is important because it helps plants make energy from sunlight through a process called photosynthesis.

The summer sunlight triggers the leaves to keep making more chlorophyll. But trees are very sensitive to changes in their environment.

As daylight hours get shorter in autumn, trees stop creating energy and the amount of chlorophyll is drastically reduced. As the chlorophyll breaks down, the green color disappears allowing the colorful autumn pigments to become visible.

Why do leaves fall off?

Photosynthesis requires the tree to use a lot of water. Since the trees are no longer creating energy through photosynthesis during the autumn and winter months, they need to conserve energy and retain moisture in order to survive.

A tree will do this by closing up the tiny holes where the leaves are connected to the tree, resulting in the leaves falling off. But fear not, the trees will grow back their leaves come springtime. These types of trees are known as deciduous trees.

What about the trees that stay green?

Some trees stay green year-round. These trees are known as evergreens. Evergreens often have tightly rolled leaves, or needles, and a waxy coating that allows the tree to retain moisture and continue making energy year-round.

Test your nature knowledge

Go for a walk around your neighborhood, a local park or the Pawpaw Trail at Discovery Place Nature. Observe the trees and count how many deciduous trees you can find. How many evergreen trees do you see? What do you notice about the shape and texture of the leaves?