Weather Holds Promise of Colorful Autumn (190)

KNOXVILLE, Tenn.– Tennessee woodlands should be filled with autumn color this fall if the weather continues to cooperate, a University of Tennessee forester said Monday.

 Dr. Wayne Clatterbuck of the UT Agricultural Extension Service said shorter days, cooler temperatures and drier air help produce the color show by slowing photosynthesis.

 “A popular misconception is that frost enhances foliage coloration,” Clatterbuck said. “A sudden frost is more likely to kill leaves, making them turn brown and fall to the ground sooner.”

 As photosynthesis slows, green-colored chlorophyll begins to disappear and unmasks other colors that have been hidden all summer long, Clatterbuck said.

 Xanthophyll gives leaves their yellow color and carotene creates an orange hue.

Clatterbuck said red pigments, called anthocyanin, don’t begin to appear until the flow of nutrients to and from the leaves stops. Sugar trapped in the leaves helps create the red pigments.

 Tree type has a lot to do with leaf color, Clatterbuck said.

Yellows dominate in hickory, birch, poplar, boxelder, sugar maple, elm and ash trees. Reds are common in the oak, red maple, sourwood, dogwood and sumac.

Various in-between shades occur in sweetgum, cherry, osage orange and beech trees.

 —

 Contact: Dr. Wayne Clatterbuck (423-974-7126)