Seeing red: Science of fall color in the Carolinas

Howard Neufeld is known as the Fall Color Guy. It’s his Facebook page – – his twitter handle (@fallcolorguy) and it’s the role he’s adopted. This biology professor at Appalachian State is one of the few scientists worldwide to study the hows and why of fall color. His color forecasts are as accurate as they get, and he’s worked with everyone from the N.C. Division of Tourism to Explore Asheville to get the word out about Western North Carolina’s fall leaves. Why? Because he loves fall, has a passion for the science behind the beauty, and because he wants you to get out and enjoy nature in all its glory.

Q. What gave you the passion for leaves and the science behind why they change colors?

A. I grew in Fredrick, Md., right at the base of the first chain of the Blue Ridge. In the fall, my family would take hikes. We’d go to Washington Monument State Park and watch the maples and oaks turn beautiful colors. Little kids like to slosh their feet through the leaves so since I was a kid, I’ve always liked the season.

After I got a job with Appalachian State in 1987, I was introduced to this little plant that grows in the woods here called galax. It was obvious that this was an interesting plant because in the fall, the leaves would turn a bright red if they were in the sun. I realized no one had studied it much, so I kept an eye on it, looking for a research opportunity. A student was interested, so I asked her, “Why does galax turn red in the winter? And does it turn back green?”

She took it and ran with it, and we published a major article in the International Botanical Journal that showed that the red seemed to act as a light screen, protecting those leaves in the winter because they are susceptible to high light when they’re cold. Right about that time, two independent sets of researchers came out with the same hypothesis – that the red color may protect those leaves from getting too much light in the fall and help the plants retranslocate nutrients from the leaves back into the twigs so they can store them and use them for next year’s leaves. That made me start to look more closely at fall color.

Q. So, in essence, the color change is slowing the flow of energy so the tree can redirect it later?

A. Well, sort of. All trees tend to withdraw nutrients back into their twigs. They spend all summer taking those nutrients up and storing them in the twigs for the new leaves that come out in the spring. The hypothesis with galax was that the red color filters out some of the light so the leaves can continue to take their nutrients in.

Word of my research got out, and people started calling me saying, “What do you think the color’s going to do this fall?” And I started telling them what I thought. It wasn’t based on much beyond experience, but as it turns out, there wasn’t a lot of science out there on what makes for a good fall color season.

Q. What makes North Carolina’s color season so popular?

A. In New England, which is known for its fall color, they have relatively fewer trees that turn color. Down here in the southern Appalachians, we have up to 120 different tree species, maybe 125 in Great Smoky Mountains National Park, that’s the highest tree diversity in the United States. We have a lot more potential for a diversity of color down here.

The other thing in North Carolina is the incredible elevation gradient. We’ve got the highest point in the Eastern U.S. at Mount Mitchell and the second tallest in Clingman’s Dome; then you go all the way down to Charlotte where you’re only 750 feet above sea level. The fall colors start earlier at the higher elevation – it gets colder sooner there – and you can watch this wave of color move down the mountains at about 1,000 feet every week to 10 days. That means our fall colors can be spread out over a month and a half whereas in New England it’s about a two-week period; then it’s gone.

For visitors, this means you could see fall color on five or six consecutive weekends.

Q. Why do leaves change? I always heard it had to do with sugars

A. In trees that just turn yellow or orange, generally those are compounds called carotenoids. These compounds are in the leaf all summer, and they assist with the photosynthetic process. But they’re dominated and covered up by the green chlorophyll. When the chlorophyll begins to break down, it becomes colorless, allowing the other pigments to show up; that’s how you get the yellows and the oranges. Trees that turn red actually synthesize this pigment called anthocyanin in the autumn just before the leaves fall.

Q. It sounds a lot like harvesting grapes. Sunny days, cool nights, the sugars concentrate and you get better wine.

A. Exactly. And the colors in grapes are anthocyanins. Same pigment. A lot of what we know about anthocyanins has come from people studying grapes.

When you have sunny days in the fall, the trees can do photosynthesis and make those sugars. The cool temperatures tend to slow down the movement of the sugars out of the leaf, so the sugars build up, which triggers a lot of anthocyanin production. That’s why if it’s rainy or cloudy or warm in the fall, the colors look a little duller.

That’s what makes August and September important for good fall color: That’s when the trees are determining how much anthocyanins they make. If it’s rainy in August and September, you get fewer anthocyanins and dull color. If it’s sunny and cool, as it was this year, that’s the perfect set of conditions to make this pigment. August and September were ideal this year.

Q. Do you have a favorite tree?

A. The red maple is my favorite because it turns such bright colors. And it does it in an interesting way. The leaves start to change at the top of the tree and on the side facing the sun. You’ll have a tree with a whole red top and the bottom is green.