JACKSONTOWN– So many people agree autumn is their favorite time of year, with the cool days and spectacular trees. For color, this year’s autumn was, well, okay. “Comparison-wise, we’ve had better,” said Dawes Arboretum Director of Horticulture, Mike Ecker. “If hard frost holds off for another week or so we should continue to see nice color.”
So, why do leaves change? According to Science Made Simple, leaves are nature’s food factories. Plants take water from the ground through their roots. They take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into oxygen and glucose. Oxygen is a gas in the air that we need to breathe. Glucose is a kind of sugar. Plants use glucose as food for energy and as a building block for growing.
The way plants turn water and carbon dioxide into oxygen and sugar is called photosynthesis, which means, “putting together with light.” A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color.
As summer ends and autumn comes, the days get shorter and shorter. This is how the trees “know” to begin getting ready for winter.
During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves.
As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along. We just can’t see them in the summer, because the green chlorophyll covers them up.
The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color.
The brown color of trees like oaks is made from wastes left in the leaves.
It is the combination of all these things that make the beautiful fall foliage colors we enjoy each year.