Fall Colors Explained Oct 18, 2017

Most of the country is enjoying very mild fall weather perfect for doing some leaf peeping this week.

Some locations across the country have already seen peak color change in the foliage but there is still plenty of color left to enjoy this year.

We witness leaves changing color each fall but what really happens to bring about the vibrant colors of the season?

Many people believe the colder temperatures of the fall season initiate the color change in the landscape, but; that isn’t the whole story.

Cooler temperatures and drier air do play a part in changing leaf color from green to red, yellow, purple, black, orange, pink, magenta, blue and brown, but the real reason behind the change in color is the declining sunlight hours through the season.

It’s the shortening days in autumn that are the trigger in the chromatic change but it’s chemistry that does the heavy lifting.

During spring and summer, while the leaves on trees are green the trees are an active chemistry lab, conducting reactions in photosynthesis.

During the photosynthesis process, plants will take in carbon dioxide from the air and use sunlight to turn water and carbon dioxide into oxygen and glucose.

Plants use the glucose produced as a building block for growth and expels the oxygen. The chemical reaction of photosynthesis reduces carbon dioxide and produces oxygen and glucose that the plant needs, is made possible by the chemical chlorophyll.

Chlorophyll is the chemical that gives plants their green color and is actively present in leaves when photosynthesis is occurring.

As the days grow shorter, especially through late summer, fall, and winter there is not enough sunlight for photosynthesis to occur.

The plants during this time will begin shutting down the photosynthesis “operation” in preparation for winter and the “green” chlorophyll will disappear from the leaves.

Some of the colors we see as the leaves change, were actually present in the leaves during the summer months too. For example the reddish color of oak leaves in fall was there in summer, it was just overshadowed by the abundance of green chlorophyll.

Weather does play a part changing the colors that we enjoy each fall. Early frosts, rain, and prolonged cool temperatures can enhance or even dull the colors of the season. As we move further into fall enjoy the new colors of the season and also raking up those leaves after they plummet to the ground.

 

Meteorologist Mike Morrison

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