Fall foliage: Science professors weigh in on understanding the changing of the leaves

Photo by Rachael Anne Keisling / MTSU Sidelines

Story by Katrina Johnson / Contributing Writer

It’s the time of year when Mother Nature puts on a show of color, but the question is will the forests offer vibrant yellows, oranges and reds, or will the mountains only offer shades of brown?

Will they even be worth leaving home to see?

According to Chris Herlihy, a biology professor at Middle Tennessee State University, the answer depends on a number of factors.

“The all-of-a-sudden change in weather can result in sharp colors in the fall leaves,” Herlihy said. “Tennessee has more of a gradual change in weather, so it’s hard to tell what colors the leaves will be.”

Indeed, predicting the fall colors can be difficult, because there are so many variables that determine the intensity and timing of the foliage change.

First, it’s important to understand the biology behind the process. In the fall, chlorophyll is replaced in the leaves, and as the chlorophyll breaks down with the exposure to light, its green color is replaced with others, according to the United States National Aboretum, whose website offers a detailed explanation of what happens this time of year.

When chlorophyll disappears, other pigments such as xanthophylls and carotenoids (yellow and orange, respectively) are able to shine through. Red and purple come from anthocyanins, another pigment that shows only after the growing season has come to an end.

Wayne Clatterbuck, a forestry science professor at the University of Tennessee at Knoxville, noted that seeing fall’s color show doesn’t have to mean travelling far.

“Leaf color occurs everywhere so you do not necessarily have to leave metro areas to observe leaf color,” Clatterbuck said. “Many of the more rural roads have excellent leaf color.”

In the mountains, he noted, tree cover is more continuous.

“The other advantage in the mountains is that you can watch the progression of leaf color with the change in elevation,” Clatterbuck said. “When leaf color is prime in the valleys, leaves have already been shed at the upper elevations.”

So how vibrant will leaf color be this fall?

“Much depends on the weather and how moisture and temperature influences leaf Pigments,” Clatterbuck said. According to him, it’s really the “change in day and night temperatures that influences the color. Day and night temperature and the amount of sunlight — if there isn’t a lot of overcast — will determine how intense the leaf color will be.”

But only Mother Nature knows for sure.

Best places to view fall foliage


  • Grove of trees near Peck Hall

One hour or less from campus:

  •       East on State Highway 96 toward Auburntown
  •       East on State Highway 70S toward Woodbury

Two hours or less:

  •       State Highway 70S to McMinnville and then State Highway 30 to Spencer and Pikeville
  •       I-24 East to Monteagle and then east or west on State Highway 64

Three hours or more:

  •        Great Smoky Mountains National Park and Gatlinburg area
  •         Big South Fork National River and Recreation Area, Jamestown, Tennessee

To contact Lifestyles Editor Tayhlor Stephenson, email lifestyles@mtsusidelines.com.

For more updates, follow us at www.mtsusidelines.com, on Facebook at MTSU Sidelines and on Twitter/Instagram at @Sidelines_Life.

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