Revealed! Fall Leaf Secrets

Experts share why leaves change and predict when to hit the road for the colorful show.

- Sheryl Devore

Athy Mathews loves to watch the sugar maples turn yellow, orange and red at Great Smoky Mountains National Park near her home. “Sometimes you’ll see all three colors on the same leaf,” she says. An associate professor of biology at Western Carolina University, Kathy has spent 10 years studying and predicting peak viewing time for fall colors. She still marvels at the magic of fall, when green leaves transform into brilliant eye-catching copper shades.

This phenomenon occurs when trees stop producing chlorophyll, a green substance in leaves that interacts with sunlight throughout spring and summer to make food for trees to grow. Changing weather conditions in fall tell the trees it’s time to store sugars in the roots for next year’s growth. As the cool temperatures approach, daylight hours shorten and the chlorophyll breaks down, revealing the bright hidden hues.

“It is more efficient for the tree to do this than to maintain its leaves year-round,” Kathy says. Some trees, including maples, even create a new pigment—a deep rich red.