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fall leaves

AUBURN UNIVERSITY, Ala. – A rush of color has invaded Alabama yards and forests. Leaves are transforming the state’s color palette, and this natural change correlates to autumn’s cool temperatures. From red to purple, an Alabama Cooperative Extension System home grounds, gardens and home pests regional agent explains the shades of the season.

Leaf Composition

Mallory Kelley, Alabama Extension regional agent, said it is important to understand the science of leaf composition before their color variety.

“Leaves are made of living plant cells,” Kelley said. “These cells typically appear green because of the pigment, chlorophyll.”

Chlorophyll relies on ample amounts of sunlight to produce food for a plant during photosynthesis, the food-making process of a plant. When fall arrives, days shorten and the necessary amount of sunlight wanes. Kelley said this reduction of resources causes the chlorophyll in leaves to change color over time.

“As days begin to shorten, so does the amount of sun available to the leaves,” she said. “Therefore, the living plant cells in leaves do not receive enough light to create food and begin to change color.”

Autumn’s Palette

The colors of fall leaves are yellow, red, orange and purple. Most people who value autumn have their favorite shade. What is arguably the most satisfying is when all colors are present at the same time. In Alabama, fall color can arrive earlier in some regions. The northern portions of the state are typically colder in climate, which seems to invigorate and start the state’s fall transition.

Kelley said there is one species in particular that reveals when the leaves are beginning to change each year.

“The initial plant that tells me fall is here is the terribly invasive popcorn tree,” Kelley said. “You will start to notice them along fence rows and out in pastures along the roadsides.”


The color yellow is in every leaf. It takes the right reduction of light and temperature to break down chlorophyll into this bright shade.

According to Kelley, hickory and ginkgo are some of the most prominent trees that typically turn yellow in autumn. The amount of precipitation prior to the beginning of fall can determine what color a hickory turns at fall’s temperature transition.

Orange, Red and Purple

Each leaf will begin as yellow and transform into more shades of orange, red and even purple. Kelley said warm, sunny days with cool night temperatures–especially below 45 degrees F–will give leaves these extravagant shades.

These temperatures trap the sugars produced during the warm sunny day inside the leaves, producing the array of fall colors. However, certain tree species will only show one type of colored leaves.

“The colors can vary tree to tree based on factors like physical location or even genetics,” Kelley said. “Also, they can vary on the same tree.”

A Natural Phenomenon

Now is a better time than ever to explore Alabama’s transformed landscape. Try a new hobby by collecting the best fall leaves in every color. Even a friendly competition may be in order to see who can find the perfect examples. For more information on fall leaves, search leaves on the Alabama Extension website at www.aces.edu.

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