“The mellowing year marks its periods of decline with a pageantry of hues so varied that it is, as Walt Whitman said, `enough to make the colorist go delirious.’ Here in the forests of the Blue Ridge, where well over a hundred kinds of native deciduous trees are to be found, the spectacle challenges description; the writer feels humbled and gropes for words.” – Arthur Art Stupka in Roderick Peattie’s “The Great Smokies and the Blue Ridge” (1943).
The forests of the Smokies region contain an array of deciduous trees, shrubs and vines that put on a show each fall that lead leaf-pilgrims to flock into the region from all over the world. Their motivation is admirably aesthetic. Some that show up this year will have been coming every year for half a century or more. It’s also an economic bonanza. Pilgrims require food, lodging, T-shirts and a lot of other things.
The fall color cycle upon which both aspects (spiritual and economic) are based is relatively simple. Spring and summer leaves are green because of chlorophyll, the pigment that enables leaves to manufacture food via photosynthesis. Leaves also contain other pigments at this time, but the dominant green of the more abundant chlorophyll masks them.
There are two basic factors involved in fall color.
The first is constant from year to year. With late summer and fall’s shorter days, the leaves stop producing as much chlorophyll. Other colors (especially yellow) emerge as pure pigments. Carotin and other yellow pigments cause pawpaw, spicebush, witch-hazel, mulberry, hickory, black locust and other species to glow softly in the woodlands like candles.
The second varies from year to year. A cool snap of about 35- to 37-degrees F. in late September or early in October (usually before Oct. 10, our average true frost date) activates the formation of a corky layer at the point where the leaf stems connect to their twigs.
The connection is indicated by a swollen nodule that botanists call the “abscission layer.” As the nodule hardens the flow of water and minerals to the leaf is cut off so that it can no longer produce any chlorophyll at all.
At this point the previously masked colors really start to appear. Compounds called anthocyanins brighten the landscape with reds and oranges. If the leaves contain significant amounts of tannin – as is the instance with the various oak species – brown and maroon are dominant.
Those leaves that contain significant amounts of sugar – as does sugar maple – undergo a chemical reaction that results in the brightest red colors.
I like best that portion of the color cycle in late October and very early November, when all of the muted colors swirl and intermingle as if in a kaleidoscope or an abstract painting.
George Ellison is an award-winning naturalist and writer. His wife, Elizabeth Ellison, is a painter and illustrator who has a gallery studio at 155 Main St., Bryson City. Contact them at [email protected] or [email protected] or write to 3880 Balltown Road, Bryson City, NC 28713.