By Sandi Martin
University of Georgia

The professor of tree biology at the University of Georgia Warnell School of Forestry and Natural Resources has come close just once to finding it. That close call was a tree that had been damaged by chemicals. Even then, it wasn’t the real color he was looking for.

Rarest of all trees, he said, is the “Holy Grail for fall color – the tree that is true blue.”

Instead, he sees what everyone else does at this time each year – a vibrant array of yellows, oranges and greens, as leaves take on their autumn colors, signaling the onset of colder weather and making way for spring flowers to bloom.

Coder predicts that this year’s leaf changing season will be a great one, despite some less than ideal conditions that will likely affect the vibrancy. Barring any major storms that cause the premature falling of leaves, the peak leaf color change will be around Nov. 6. This is the time the color orange will be most dominate throughout the landscape.

The peak, however, has been coming later in recent years.

It’s now 10 days later than it was 18 years ago, Coder said, likely because of regional climate change. Warmer temperatures at night and during the day have affected when the leaves start the process of changing colors before falling.

That means the leaves are in danger of being killed by frost before they fully color because “we still haven’t changed our first heavy frost date by much,” Coder said. “We’re going to run up against a heavy frost date that may kill leaves by mid-November.”

This fall, the color season will run later and longer, with landscape colors spread over more days.

Essentially a biochemical process called senescence, color changes indicate trees going into a resting phase. It happens because trees are recovering valuable resources from the leaves and discarding what they don’t need.

Spring flowers count on those recycled leaves so they can bloom, Coder said. Leaf colors can range from green-yellow through orange and red to purple-blue. The majority of trees end up with yellow and orange leaves with red and dark purple leaves occurring late into fall.

“So many things go into making fall colors,” he said, “and few years have perfect combinations.”

The ideal conditions for vibrant autumn colors, Coder said, are:

* Cool nights.

* No freezes or frosts.

* Warm, bright and sunny days.

* No drenching rains or wind storms.

* Slight drought conditions.

* Healthy trees.

The species of tree determines what color its leaves might turn during this process. For instance, dogwoods typically turn red or reddish-purple.

The further south one moves, even to just Macon or Cordele, Coder said, the colors become less vibrant.

Leaf color also indicates the tree health. A sickly looking tree is in poor condition and will look pale and yellow.

“A bright color is a sign of a healthy one,” Coder said.