Why Do Leaves Change Colors in the Fall

Ever since the leaves on the trees bloomed in the spring, they have actively been helping the tree grow. Each leaf contains a pigment called chlorophyll. Chlorophyll is the most common pigment in a leaf. It absorbs the sun’s rays to turn sunlight into food and energy for the tree. Chlorophyll is also what gives a plant its green color.

Admiring the vibrant red leaves that add so much color to Acadia's fall landscape. NPS Photo/Hadley Seymour

When the temperature drops and there is less daylight, the tree begins to conserve the energy it generated in the spring and summer months. One way trees save energy for winter is by dropping their leaves. As autumn progresses, a tree will send a substance to each leaf called an enzyme that is directed to take apart chlorophyll pigments. Once the chlorophyll breaks down, the other pigments that weren’t visible to the human eye before are now on full display! Every tree has a different combination of pigments remaining which gives leaves their unique colors. The pigments found in fall leaves can also be seen in other common plants. A good example of this is carotene, the pigment responsible for orange leaves. It is the same pigment that makes a carrot orange!

A visitor enjoys the fall landscape on the coast of Maine NPS Photo/Hadley Seymour

The temperature and rainfall can affect the brightness of the fall colors. When there is more rain, the colors pop even more! When there is a cool fall, the red maple leaves appear brighter as well. Once the chlorophyll has been broken down, the tree will take the last of the nutrients left in the leaves and absorb it back into the branches and trunk before each leaf falls to the ground.

Index:

• Enzyme: a substance in plants and animals that can perform specific tasks to keep plants and animals functioning
• Pigment: the natural color of plant or animal tissue

Citations:

• Britannica Kids, Encyclopædia Britannica, Inc., kids.britannica.com/students/article/enzyme/274186.
• “Chlorophyllase.” ScienceDirect Topics, ScienceDirect, www.sciencedirect.com/topics/agricultural-and-biological-sciences/chlorophyllase.
• Palm, Carl E. “Why Leaves Change Color.” Around Your World, SUNY College of Environmental Science and Forestry, www.esf.edu/pubprog/brochure/leaves/leaves.htm.

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