by Jeanne

We noticed this year that the foliage on the understory trees on our 17-acre timber farm in southern Virginia seems to have begun changing color a little earlier than usual.  Now we are noticing more brilliant color than normal. The snowball Viburnum in the flower garden turned a rich bronze-plum color. The dogwoods are turning soft shades of red and orange. The tulip trees scattered through the timber tracts are also turning golden yellow.

What makes leaves change color in the fall? Why do they turn later some years than others? Why are some years more memorable for fall color?

The USDA Forest Service website provides an excellent explanation, which I’ll do my best to summarize here.  Although the leaves of deciduous trees and shrubs appear green from spring to the fall, throughout the leaf there are pigments called carotenoids and anthocyanins. The changing daylight hours signal the vessels inside the trees’ leaves to shut down, which shuts off the production of chlorophyll. As chlorophyll levels decrease, the green colors fade, and leaves “turn” colors.  It’s more like a window shade is pulled up to reveal the interior of the room; the green chlorophyll masked the true color of the leaves throughout the growing season.

Why are the colors more brilliant this year than in past years on our farm? That’s thanks to two factors which can influence the colors and timing of when leaves turn colors in the fall: weather and water. First, warm days and cool nights tend to produce more brilliant color, and we’ve already had one cool spell in September, and this weekend temperatures are expected to plunge into the 40s and night and the 70s during the day, which should produce optimal leaf color.  Droughts in spring and summer can make colors more dull, while adequate rainfall encourages higher production of the pigments that produce color. Given the abundant summer rains we’ve had, that should also add to a brilliant autumnal display as the leaves turn color in the fall.

Although the timing and color of the leaves is set by genetics – oak trees turn colors at the end of the fall, and some trees always turn shades of yellow, for example – there is variation from year to year.  It’s not just your imagination. It’s science!

Whatever you call it, it’s beautiful, and it’s also my signal to increase my efforts to preserve the harvest before the true frosts arrive.  So I’m off now to can some garden carrots and peppers.  But I will definitely take time to enjoy the colorful display this weekend and enjoy a taste of fall.