All About Autumn
Why Leaves Change Colors
Story by Katie Gorman
It will be a colorful autumn in northwest Ohio. That's never in dispute. How colorful, however, depends on factors that only Mother Nature controls.
The vibrancy of fall colors is different from every year, and the weather leading up to fall can make all the difference, said Metroparks naturalist Bob Jacksy.
"If the days are cloudy and it is warm going into fall, the leaf color can often be very mediocre," Jacksy said. "It take sunny days and cold nights to make the best fall color. The sun will help the leaves make more sugars and the cool nights keep the sugars bound-up in the leaves, ergo more splendid color."
So, why do leaves change, any way?
"Leaves change color in the fall because the trees stop manufacturing chlorophyll as the days grow shorter," said Jacksy. "After chlorophyll, a green pigment, is no longer produced, you see the pigments that underlay the green chlorophyll."
"There are lots of other colors in leaves all the time," added Metroparks naturalist Kim High. "The colors a leaf will show depends on the chemical changes that occur in a specific season."
Autumn leaves can be red, orange, yellow, or all three.
Red leaves are a common sight in the Metroparks, thanks to a vine called Virginia creeper, which is known for producing fierce red leaves in fall. The intense red colors of fall are produced from the byproduct a sugar called anthocyanin within the plant leaves.
Yellow leaves are commonly seen on cottonwood trees, which produce "cotton"-covered seeds in fall. The bright yellow pigment some fall leaves take on is due to carotenoids, a chemical present within chloroplasts, whose green color fades as the photosynthesis process slows to a stop.
Orange leaves are characteristic of beech/American beech trees, which also produce small, sharply-angled nuts in fall. This rich orange color is produced by the combination of anthocyanin byproduct and carotenoid chemical - a combination of the chemicals which make red and yellow leaves.