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Why Do Leaves Change Color?
Goodbye Summer, Hello Fall!
The first day of fall is just around the corner---Tuesday September 23 to be exact. For those of us that may need a bit of a refresher, September 23, 2014 is the autumnal equinox---one of two times a year when night and day are approximately equal in duration.
Terminology aside, many of us know and love autumn for its cool breezes, holiday celebrations, and visual brilliance. It's the time of year when the leaves on the trees transition from lively greens to spectacular yellows, oranges, and reds. The beauty of fall is truly a sight to behold!
Many of us make it a point to see and enjoy the annual foliage without a full grasp of the science behind what we are witnessing. Take a brief moment and ask yourself the following question: Why do leaves change color? If you find yourself unable to fully answer this question, read on!
Why do Leaves Change Color?
In the spring and summer, in a process called photosynthesis, trees use the sun's energy to convert water and carbon dioxide into sugar. Chlorophyll, which gives the leaves their green color, is necessary in order for trees to convert the sun's energy into food. As long as photosynthesis is taking place and chlorophyll is present, leaves will remain green in color.
In autumn, when temperatures fall and the number of hours of sunlight per day decreases, trees take a break from photosynthesis in preparation for the long and grueling winter ahead. Chlorophyll breaks down and leaves lose their greenish hue. Reds, oranges, and yellows begin to show, as they are the true color of the pigmentation of the leaves---we just can't see these colors in the spring and summer, as they are hidden beneath the green color of chlorophyll.
Why do Leaves Change Different Colors?
As you have likely noticed, some leaves turn red, others orange, and others yellow. What determines the specific color of a tree's leaves? Pigmentation varies by type of tree. Below, you will find listed some common types of trees and the color of their leaves during foliage season.
- Birch - The leaves of Birch trees are bright yellow in color.
- Dogwood - The leaves of Dogwood trees are purple-red in color.
- Hickory - The leaves of Hickory trees are golden (yellow-brown-orange) in color.
- Maple - The leaves of Sugar Maples are orange-red in color. The leaves of Black Maples are yellow in color. The leaves of Red Maples are bright red in color.
- Oak - The leaves of Oak trees are brown or red in color.
- Poplar - The leaves of Poplar trees are yellow in color.