CLEMSON — Record-breaking summer rains that caused creeks and rivers across the Southeast to overflow likely will bring an extended leaf-looking season to the Southern Appalachians, predicts Clemson University forest ecologist Donald Hagan.

“The wet soil means that trees should hold their leaves longer and fall colors will unfold more slowly. We’re unlikely to have the short-lived blast of color that has followed the drought conditions of recent years,” said Hagan, of Clemson’s School of Agriculture, Forest and Environmental Sciences.

During scouting and laboratory trips into middle and higher elevations with Clemson forestry and natural resources students, Hagan observed that such tree species as blackgum, flowering dogwood and sourwood are beginning to turn and some even are dropping their leaves.

“These species are photoperiodic, meaning their dormancy and leaf color is dependent on day length,” Hagan said. “Species such as maples, oaks and birches that depend on a combination of sunlight and cold for their color are in the early stages of change.”

Hagan said that leaf-lookers should observe the weather closely for the next few weeks. Crisp nights followed by clear, mild days will cause color change to accelerate.

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 degrade and other naturally occurring pigments emerge. Different pigments create different colors.

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 Southern Appalachians are known for complex topography and a multitude of microclimates,” Hagan said. “This means that to see the most beautiful fall foliage, people should explore. Just because the color isn’t as vibrant in one location doesn’t mean you won’t stumble upon a spectacular south-facing vista around the bend.”