The combination of a wet spring and forecasts for above-average temperatures this fall could produce a long-lasting leaf display in the mountains of Western North Carolina, but with spotty color development.
That’s the word from Western Carolina University’s autumnal season soothsayer Kathy Mathews in her annual prediction of how foliage around the region will perform as the sunlight of summer wanes and days become crispy.
Mathews, an associate professor of biology at WCU, specializes in plant systematics and bases her color forecast in part on weather conditions. She believes that the formation of higher levels of pigments in the leaves correlates with dry weather throughout the year, especially in the spring and September.
Predicting the quality of the fall leaf color is a combination of a science and an art, Mathews says. “Forecasters combine knowledge of environmental effects on pigment formation, climate history and forecast, and a healthy dose of observation and experience of past autumns in the region to make their best prediction,” she said.
Rainfall measurements for the Asheville area indicate that April was a very wet month, with about two inches above normal precipitation, and rainfall amounts slightly above normal fell in May and June, Mathews said.
“The rainy spring months this year portend somewhat muted pigments on the leaves in the fall,” said the fearless foliage forecaster. “On the bright side, our abundant tulip poplars, which are typically among the first trees to change color in the fall, perform well in wetter conditions, developing a golden hue that persists longer before browning. Overall, however, trees that produce red leaves, including sourwood, red maple and dogwood, perform best in dry conditions. Therefore, we may see fewer brilliant reds during the peak of fall color change.”
Still, the development of dry conditions in late August and September could improve the overall outlook and produce the best bursts of color, she said.
On the other side of the weather coin, the seasonal forecast from the National Oceanic and Atmospheric Administration calls for slightly above-average temperatures this fall in the Southeast, and if that prediction pans out, the color season could be longer than normal, extending well into November, Mathews said.
Fall foliage fans always want to know when the “peak color” will happen, but the timing of the color change is highly dependent on the decreasing amount of sunlight that comes with the passing days, plus the elevation of a particular location, she said. “The peak of fall color often arrives during the first and second week of October in the highest elevations, above 4,000 feet, and during the third week of October in the mid-elevations, 2,500 to 3,500 feet,” Mathews said. “However, the timing of the first frost is important, as well. Because freezing temperatures quickly degrade the green chlorophyll, leaves peak in color intensity four to five days after a frost.”
Several periods of unusually chilly mid-summer weather in WNC, which included some of the highest peaks of the Smokies dipping into the 30’s, already may have had an effect on some trees in the mountains, Mathews said. “We’ve been seeing very early color change already in individual trees, mainly red maples, around the western part of the state,” she said.
Regardless of all the factors that affect leaf color, visitors to Western North Carolina always will find a pleasing leaf display somewhere in the mountains from September into November, with a smorgasbord of color made possible by the region’s more than 100 tree species, Mathews said.