Good fall foliage viewing predicted, but then who really knows

Leaves should be colorful this fall in Kentuckiana.

According to the calendar, fall has officially arrived, and coming closely behind should be fall foliage. And, this year should be a colorful one.

Many of those who predict fall foliage say based on this year’s relatively mild temperatures and the amount of rainfall this summer, vivid leaf colors can be anticipated.

At the time of this writing, not a lot of color is showing, but change has started. What mostly is being seen now are dogwoods and sumac.

Predicting when the leaves will be most colorful as well as the amount of brilliance  isn’t easy. Moisture, temperature and light are primary factors. but even the best forecasters don’t always get it right and sometimes aren’t sure why.

Last summer and early fall were terribly dry and few people thought leaves would be colorful, but most people were fooled. The leaves were much more colorful than anticipated.

It seems there is a lot known about what causes color in the leaves, but predicting its intensity isn’t easy.

       Abby van den Berg, University of Vermont plant biologist, who has done research on leaf colors, said some data suggest a small amount of physiological stress can result in more brilliant colors.

"The real bottom line is that there's no great way to predict these things," she said. "It's pretty much impossible, especially over a large scale."

As to the timing, the Farmers Almanac says leaves in Southern Indiana usually reach their peak from Oct. 12-28. 

According to the Weather Channel, “Temperature, light, and water supply have an influence on the degree and the duration of fall color. Low temperatures above freezing will favor anthocyanin formation, producing bright reds in maples. However, early frost will weaken the brilliant red color. Rainy and/or overcast days tend to increase the intensity of fall colors. The best time to enjoy the autumn color would be on a clear, dry and cool (not freezing) day.

“Every autumn we revel in the beauty of the fall colors. The mixture of red, purple, orange and yellow is the result of chemical processes that take place in the tree as the seasons change from summer to winter.

“During the spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured. 

“This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch.

“Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange color to a carrot. Most of the year these colors are masked by great amounts of green coloring.

But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor.