Why Tree Leaves Turn Colors in the Fall

Posted by Denise Oliveri Sep 20, 2008

My youngest son, who is 10 years old, is learning about trees in general, and the different varieties of trees. One thing that struck him is why tree leaves turn colors in the fall. While most trees have leaves that do change colors, some do not, such as the conifers (needle trees).

Why Leaves Change Colors in the Fall

Trees receive a lot of sunlight in the spring and summer months because the days are warmer and longer. This enables them plenty of time and the resource (the sun) to turn water from the ground and carbon dioxide in the air into glucose (a type of sugar) that gives them the food they need to grow. This process is called photosynthesis, and it allows tree leaves to stay a bright green during the warmer weather. The green leaves are possible because of chlorophyll, which is a chemical in leaves that reacts to sunlight and warm weather.

As the weather starts to turn colder, trees lose the amount of sunlight they were used to getting. With less food production and the loss of chlorophyll, the leaves turn colors, signaling that it is time to get ready for winter. Trees survive the colder months by living off the food they have stored throughout spring and summer.

And in a nutshell, that is why leaves change color in the fall.

More Resources for You

Why Do Autumn Leaves Change Colors? (lesson plan)

Answers for Kids About Leaves (article)