Autumn: An Unbe-leaf-able Period of Color Transition

This weeks blog post was written by Emma O., a Drummers alumni! She writes about the interesting science behind fall foliage.

Emma O.

With holidays like Halloween and Thanksgiving, delicious comfort food, warm clothes, and all things cozy, how could one not enjoy autumn? While the season has many things to offer indoors, there is one fascinating process occurring outside that most people don’t think twice about–the metamorphosis of green leaves transforming into fluttering canvases ablaze with color.

Down in South-central Pennsylvania, the leaves are finally starting to turn!

In autumn, when the days become shorter and the temperature falls, leaves begin to make incredible changes in their chemistry. As most already know, leaves have the ability to convert the sun’s energy into carbohydrates, which they use for food; this process is known as photosynthesis. A substance called chlorophyll is responsible for these changes and is also responsible for making leaves green. However, there are more colors masked beneath the visible green hue, like yellow and orange. When autumn rolls around, leaves stop converting the sun’s energy into food, and the chlorophyll breaks down in the leaf. This process causes the green color to disappear, and it is replaced by another color that was in the leaf before. Thus, the leaves become brilliant golds and oranges. Occasionally, other changes occur during this process that causes the colors within a leaf to mix, creating reds and maroons. However, this unique action is mostly species specific.

There are only three regions in our world that contain color-changing deciduous forests: the British Isles and Northwestern Europe; Northwestern China and Northern Japan; and Northeastern America. Pennsylvania is a fantastic Northeastern spot for seeing fall foliage because it contains both southern-growing trees and northern-growing trees, and they all change color in autumn. In Pennsylvania, trees begin changing color from north to south. In the northern regions of the state, the first week of October is the time for peak color, while in the latter half of October, the south-central and southeastern regions are in peak color.

The leaves changing color at the Pennsylvania Grand Canyon.

One way to identify common Pennsylvania trees is by their color in autumn. For example, both the American Elm and Tulip Poplar turn a golden color; the Fire Cherry turns a bright orange; the Sassafras and Sugar Maple turn red; the White Ash turns maroon.

It is certainly a sight to see when all of the seemingly-everyday trees that line our streets, homes, and forests slip slowly from cool greens into striking, fiery tones. The color that envelops our area in September, October, and November is inspiring, and the science behind the process is even more fascinating!

Cover photo credit: Randy Stewart, via Flickr Creative Commons. You can view the original post by clicking here.