Clemson ecologist predicts fall colors may peak early

Full announcement from Clemson University:

CLEMSON — Leaf lookers hoping to observe the symphony of fall colors at its most vibrant might want to get a head start.

Victor Shelburne, professor emeritus of forestry and natural resources at Clemson University’s School of Agricultural, Forest and Environmental Sciences, sees signs that peak color may arrive a bit early to the Carolinas this year.

Shelburne has been teaching and performing research in forest ecology, tree physiology and landscape ecology for 24 years. During a recent transect with students, he observed that harbinger trees such as blackgum (Nyssa sylvatica), flowering dogwood (Cornus florida), sourwood (Oxydendrum arboreum) and sweetgum (Liquidambar styraciflua) are already beginning to turn and some even are dropping their leaves.

“There are good sourwood, blackgum and dogwood reds appearing in the Piedmont,” he said. “The Jocassee Gorges area in North and South Carolina is about one week ahead of Clemson with strong reds developing on sourwoods and dogwoods.

“Up near Balsam Grove, North Carolina, at around 3,000 feet, there are some brilliant reds in sourwoods and some yellows. Farther up above 5,000 feet near the Blue Ridge Parkway, there are some beautiful individual trees. It looks to me like we’re about 10 days ahead of schedule and it could be a very good year,” said Shelburne.

This means colors would be most brilliant around mid-October in the higher elevations, late October in the lower elevations and early November in the Piedmont.

The timing and quality of color is based on a complex interaction of environmental factors, such as rainfall, temperature and duration of daylight, which trigger a series of chemical processes in the leaves.

As days become shorter and nights cooler, the green chlorophyll in leaves begins to be replaced by naturally occurring pigments. Different pigments create different colors.

Pigments called carotenoids produce the brilliant yellows and browns in trees such as hickories. Aging tannins cause bronze tones in species such as beech. The leaves of dogwoods and sweetgums are flush with anthocyanin, giving them colors ranging from red through maroon to purple. A cocktail of two or more pigments brings orange tones.

The most vibrant colors come when a dryer summer is followed by crisp autumn nights. Too much cold too early can shorten the season, and a soggy, cloudy fall can reduce red-producing anthocyanin, which needs bright sunlight. Drought can cause leaves to fall before they fully turn.

“The limited summer rains came just in time,” said Shelburne. “While we’re still in a drought, we received enough rain to keep most of the leaves on the trees.”

Shelburne says the best thing dedicated leaf lookers can do is keep an eye on the weather report.

“Look for an approaching cold front. When a cold front moves through, it will wash away the haze and make for bright sunlight and ideal viewing.”