October 4, 2006 | By: Terri McLean

Viewing fall’s showcase of color is a favorite pastime of many in Kentucky. But pinpointing the best time to catch the vibrant reds, yellows and purples in the Kentucky landscape each year can be a challenging proposition.

“Predicting fall foliage is like trying to name the winner of a horse race as the horses are coming around the last turn,” said Doug McLaren, forestry specialist with the University of Kentucky College of Agriculture. “Anything can happen as leaves are changing color.”

Several factors, namely shorter days, weather and the genetic makeup of the plants, influence autumn leaf color. And because at least one of those factors – weather – varies from year to year, predicting the amount, duration and brilliance of fall foliage with any certainty can be difficult, McLaren said.

“Plus, these factors vary by plant and by geographic area,” he added.

One constant factor in determining leaf color is the shortening of days as fall approaches. As the amount and intensity of sunlight decreases, the production of chlorophyll – the green pigment in leaves – shuts down in preparation for winter. That allows other colors, which are always present in leaves, to show through.

“During this time, trees use chlorophyll faster than it is produced. This removes the green mask on leaves and the brilliant fall color show begins,” McLaren said.

On the other hand, the weather is anything but constant and affects not only the duration of the fall showcase but also its intensity.

“The amount and brilliance of the colors that develop in any particular autumn season are related to weather conditions that occur before and during the time the chlorophyll in the leaves is dwindling,” said UK agricultural meteorologist Tom Priddy. “Temperature and moisture are the main influences. …The countless combinations of these two highly variable factors assure that no two autumns can be exactly alike.”

Other weather conditions, including wind and precipitation, do not have a direct effect on the intensity of leaf color, but they can alter how long the leaves stay on display, Priddy said. Last year, the fall color show was cut short because the leaves changed colors later and, then, about the time they began to peak, rain knocked them to the ground.

The safest bet for trying to view the fall landscape in Kentucky is to aim for mid-October. That’s when the leaf colors typically peak, McLaren said. 

“Looking through our fall color change crystal ball, it looks like we will have a great fall foliage change due to the large variety of species of trees found throughout Kentucky and the near normal rainfall and temperatures that have been seen during the summer and early fall would seem to indicate that,” he said.


Doug McLaren, 859-257-2703, Tom Priddy, 859-275-3000, ext. 245