It's a fabulous fall - and our expert can explain why all those colors come out this time of year

Autumn has arrived.  And as we all take time to welcome this wonderous palette that nature delivers year after year, those who are curious about all those colors are looking for answers.

Why there are so many different shades, tints, and tones?

What causes the colors to change?

And where's the best place to find one of nature's finest displays of leaves?

It's a topic that comes up every year, and recently Connecticut Public Radio connected with UConn's Bob Fahey to get some of the answers about autumn in New England.

I ventured into a forest in northeastern Connecticut with two UConn tree experts. We met up at Horsebarn Hill, one of the best viewpoints in the state, surveying a rolling river valley showing off with fall colors.

We see oaks just starting to turn red. Nearby hickories provide a dash of yellow – and, of course, the maples are already stealing the show, even on a cloudy day.

Here’s what I found out:

Our trees are diverse

One reason the foliage is so good is simply due to the number of species we have.

“We have a very diverse hardwood forest in this part of New England,” said Bob Fahey, an associate professor and forest ecologist at UConn. “We have both species that are more southern species and also some of the more northern species.”

“In comparison to say, the Mid-Atlantic or other places that have lots of deciduous species, we have maples, which are just the best,” he said.

“We also have a number of species that have nice yellow foliage,” he said. “Birches and beech. If you go a little bit farther south from here, mostly what you have is oaks. And oaks can have good fall foliage colors, but there are a lot of times they don't and they don't last for as long.”

We have lots and lots of trees

The diversity of species provides a diversity of color, said Tom Worthley, an associate extension professor and a forester at UConn.

He asked me to remember the last time I flew over Connecticut. What did you see, he asked. Lots of trees, right?

“Most of the ground is covered by a tree canopy,” Worthley said, noting that some estimates put that tree canopy cover at around 75% of the land area of the whole state.

“Back where we were standing a few minutes ago, we had some cherry trees,” Worthley said, his eyes scanning the trees enveloping us. “There's a few remnant ash, there's some walnut around the edges here. And let's see, some hickory.”

A walnut tree towers over us – and there are even some white pines.

It’s that varied bioscape that sets New England forests apart.

“Even in my two-acre forest behind my house, I have 22 different species of tree, which is more than some regions of the northern part of the U.S.,” Fahey said.

Travel to the west, and what you’re likely to see are lots of evergreens and aspen trees.

“Not that there aren't others, there are plenty of others, but not in the same abundance and not in the same kind of mix that we have around here,” Worthley said.

Climate plays a role

Across New England are rolling hills with microclimates that can contribute to vibrant fall colors.

“You’ll see ... highly different color in different parts of the landscape, which has to do with temperature differences,” Fahey said.

Combine that with Connecticut’s mix of southern and northern species and the colors here might not be as exciting and bright as what you would see in Vermont and New Hampshire, Fahey said. But our foliage season can sometimes last a little bit longer.

One reason? Oaks.

“We have so much more of that oak component,” Fahey said. “The oaks will hold their leaves until the end of October.”

Moisture, temperature and the amount of daylight all contribute to how long it takes for a tree to shed its leaves. And, for each species, the calculation is different.

“A tree makes an economic decision,” Worthley said. “It decides, ‘Well, it's costing more in energy to keep these leaves going than what they're producing for me and so it's time to shut them off.’”

Why do leaves fall anyway?

It’s when leaves are green that the most important work is happening, pulling carbon out of the atmosphere and giving us oxygen.

And for that green color, we can thank the pigment chlorophyll.

“The color that's in the leaves – is always there from the time the leaf is grown,” Worthley said.

“As the growing season fades, the chlorophyll disappears,” he said.

Then the other colors in the leaf can begin to show off.

Pigments like anthocyanins (reds and purples) and carotenoids (yellows and oranges) peek out, tiny threads in an autumnal blanket transforming New England’s green forests into a richly colored landscape.

The colors are out - but only for a limited time.  If you're a journalist looking to know more about this topic before all the leaves fall, then let us help.

Dr. Fahey is an Associate Professor in the Department of Natural Resources and the Environment and Center for Environmental Sciences and Engineering at the University of Connecticut.

He is also the George F. Cloutier Professor in Forestry, director of the UConn Forest, and associate director of the UConn Eversource Energy Center. Simply click on his icon now to arrange a time to talk today.