Perhaps you've noticed that in some years that the red fall colors seem brighter and more spectacular than in other years. And every year people can't seem to remember if it's a cool fall, a warm fall, or late summer rains that make the most brilliant fall colors says Jeff West, County Director, University of Illinois Extension Henry-Stark Unit.

When a number of warm, sunny autumn days and cool, but not freezing, nights come one after the other, it's going to be a good year for reds. In the daytime, the leaves can produce lots of sugar, but the cool night temperatures prevent the sugar sap from flowing through the leaf veins and down into the branches and trunk. Anthocyanins to the rescue! Researchers have found out that anthocyanins are produced as a form of protection. They allow the plant to recover nutrients in the leaves before they fall off. This helps make sure that the tree will be ready for the next growing season. Anthocyanins give leaves the bright, brilliant shades of red, purple, and crimson.

The yellow, gold, and orange colors created by carotenoid remain fairly constant from year to year. That's because carotenoid are always present in leaves and the amount does not change in response to weather.

The amount of rain in a year also affects autumn leaf color. A severe drought can delay the arrival of fall colors by a few weeks. A warm, wet period during fall will lower the intensity, or brightness, of autumn colors. A severe frost will kill the leaves, turning them brown and causing them to drop early. The best autumn colors come when there's been:

• a warm, wet spring,

• a summer that's not too hot or dry, and

• a fall with plenty of warm, sunny days and cool nights.

This information would indicate that fall colors might be a little more muted than normal depending on the weather in the next two weeks or so.

Source: Jeff West, County Extension Director, jwest@uiuc.edu