Fall foliage: Where, when and why the leaves change

By Josh O’Gorman | Stowe Reporter

Josh O'Gorman
Sep 19, 2019
Sep 19, 2019 Updated Jan 16, 2020
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As the days grow shorter and the nights grow cooler, countless people will flock to Vermont’s mountains and scenic byways for foliage season.

Much like mud season, that other unofficial spell in Vermont, foliage season is not specifically defined by the calendar, but by the changing weather and the impact it has on the state’s terrain. Unlike mud season, however, foliage season is breathtaking in its beauty and not to be missed.

Typically running for three to four weeks and beginning toward the back half of September, the changing of the leaves usually begins in the northern end of the state and at higher elevations throughout Vermont, with the change making its way south and down the mountains to the valleys.

While the change is visually stunning — with maple, ash and elm trees changing from green and yellow to orange and fire-red — the fact they change at all is a miracle of nature.

In truth, the leaves always contain these colors, but they are masked during the spring and summer by the green of the chlorophyll within them, which absorbs the light that is used as energy to transform carbon dioxide and water into carbohydrates such as sugar and starch, which the tree uses as nourishment.

It is only in the fall, when — triggered by the light cycle and cooling temperatures — the chlorophyll breaks down, allowing the underlying colors to be seen.

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Exactly how long the foliage will last, and how bright it will be, is a function of how healthy the trees are, and how the weather will be during the next month.

“We’ve had pretty average rainfall this year,” said Robert Haynes, a meteorologist with the National Weather Service in Burlington, who noted that with the rain this summer and fall, Vermont’s forests should be healthy.

“Over the next month, we’re looking at temperatures that will be consistent with what we usually see during this time of year,” Haynes said.

In short, the trees have been fed and the weather is looking optimal for foliage.

“The trees have done their part. We’ve had a good summer of growth and Vermont’s forests are healthy,” said Michael Snyder, commissioner of the Vermont Department of Forests, Parks and Recreation. “What we’re really waiting for is for the days to get shorter and for the nights to get cooler to trigger the next level.”

While the weather is uncertain, the days will undoubtedly grow shorter. Today, Sept. 19, there will be 12 hours and 20 minutes of daylight; three weeks later, on Oct. 10, it’s down to 11 hours and 17 minutes.

“Right now, the fade is on, the fade from green into yellow,” Snyder said as he looked out his window while driving across the state from east to west. “It’s a little bit dusky, and not vibrant, and that’s why we need that cold weather, and I think we’re set to have a good foliage season.”

In addition to being a state commissioner, Snyder is also a Stowe resident who appreciates the beauty of the region.

“We get a little but of everything,” he said. “We have the mountains, we have the lowlands.

“Things are looking really great in Lamoille County, and we are lucky, with our topography and our land use, to have some of the best fall foliage in the state.”

Sharon Harper, marketing manager for the Stowe Area Association, said there’s plenty of fall color on display right now.

“This year, the foliage seems to be popping right in front of our very eyes, and at a slightly quicker rate than last year,” Harper said.

“There’s a decent amount of color already, and with the rainy, wet spring and relatively temperate summer we’ve had, we’re hopeful our leaves will show their true colors and it will be another spectacular leaf-peeping season that brings visitors to town.”