Leaves turning color early this autumn

It was a relatively cool and damp summer in much of the Midwest, and leaves have started turning color. Some forecasters say leaf color change is earlier this year.

Forecasting just when leaves will turn color and reach their maximum brilliance isn’t easy to predict. However, some forecasters expect much of the Midwest to be ahead of the average this year.

According to the Farmer’s Almanac, the primary time for full color in the northern half of Indiana is Oct. 5 to Oct. 21, and the dates for southern Indiana are Oct. 12 to Oct. 28.

The leaf color depends on many factors from the type of tree to weather conditions and more, and while muck is known about the color of leaves and when they will fall, there also are unknowns and predicting the color peak is really tough.

In several recent years when summers were hot and dry, it was thought color would be dulled. However, pretty leaves still seemed to prevail in many areas.

Most autumn seasons, I enjoy the turning of leaves and also respond to questions about them. with information provided by people with much more knowledge of botany than this old scribe.

       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."

The prognosticators predicting less color last year may have been partially right, but there is was color in areas, than many anticipated. 

Drought some years causes trees to switch to survival mode. When dry conditions exist, some trees lose their leaves before they change to the familiar red, yellow or orange, according to nature experts.

 However, this spring and summer there was plenty of rain, and trees were loaded with healthy, green leaves. They are green because they contain chlorophyll. 

According to one agriculture department website, there is so much chlorophyll in an active leaf that the green masks or overpowers other pigment colors. Light regulates chlorophyll production, so as autumn days grow shorter, less chlorophyll is produced. 

The decomposition rate of chlorophyll remains constant, so the green color starts to fade from leaves.

While that is happening, increasing sugar concentrations cause increased production of anthocyanin pigments. Leaves containing primarily anthocyanins will appear red. 

Another type of pigment, carotenoids are found in some leaves. Carotenoid production is not dependent on light, so levels aren't diminished by shorter days. Carotenoids can be orange, yellow, or red, but most of these pigments found in leaves are yellow. Leaves with good amounts of both anthocyanins and carotenoids will appear orange.

Temperature affects the rate of chemical reactions, including those in leaves, so it plays a part in leaf color. However, it's mainly light levels that are responsible for fall foliage colors. Sunny autumn days are needed for the brightest color displays. Overcast days will lead to more yellows and browns.

Whether or not you care about anthocyanins or carotenoids, there should be plenty of beauty to be found this autumn.

A live leaf camera at several Indiana sites can be found on the internet at:www.chiff.com/travel/indiana-foliage.htm