Drought leaves mark on fall colors

COLUMBIA, Mo. - This summer’s drought in central and southwest Missouri is leaving its mark on the fall landscape. Don’t expect the usual showy display of red, purple and yellow foliage, says a forestry professor at the University of Missouri-Columbia.

"Trees that have been affected by the drought won’t color as much," said Steve Pallardy, MU Forestry Department chairman. "We will still get color, but it won’t be as vibrant."

Leaf color in Missouri generally peaks around the second week of October, when shorter days trigger the change in pigmentation. Bright, sunny days with highs in the 50s and 60s followed by cool nights with lows in the 40s favor the development of brilliant colors.

"You get color every year. It’s just a matter of the weather cooperating during that peak time," Pallardy said. "Cloudy days with high temperatures or even sunny days with high temperatures will make the colors less intense."

But dry weather this summer in some areas of the state will affect the coloration of some trees such as sugar maples, which won’t be as colorful this year, Pallardy said.

"I’ve also seen leaves on some hickories browning and curling rather than turning their typical yellow color," he said.

Even areas hit hard by the drought should experience a colorful display along creeks and river bottoms where trees were less affected by dry weather, said Justine Gartner, forestry field programs supervisor for the Missouri Department of Conservation.

"But if you look up into the hillsides where there is very thin and shallow soil, you will see oak trees that have already turned brown," she said.

At the end of the growing season, the trees recover these nutrients by breaking down their chlorophyll. In the process, yellow pigments that had already been present but were masked by the chlorophyll are revealed, and the leaves turn yellow. Trees whose leaves turn red or purple, such as sugar maples, sumacs and sassafras, undergo a different process. The color is the result of new pigment, called anthocyanins, that forms during the fall from sugars in the leaves. Until recently, little was know about their function.

According to Pallardy, trees whose leaves turn red and purple may do so as the result of a nutrient-recovery process. Trees invest nutrients, such as nitrogen, in the green chlorophyll in their leaves and some research indicates that anthocyanins might help serve as a protection from destructive bright light as nitrogen is moved out of leaves back into the stem and roots. That’s why the most intense red and purple fall colors often form in leaves in full sunlight.

Gartner said the most beautiful fall foliage this year in Missouri will be in the northeastern and southeastern parts of the state where there were reasonable amounts of moisture this summer.

However, folks in Central Missouri can still enjoy the colorful display of Virginia creeper, poison ivy and smooth sumac, a common roadside shrub, which are in the process of turning red, Gartner said. Small trees such as sassafras and dogwoods also are changing color; so are larger trees such as white ash, hackberry and elm. Most black walnuts and cottonwoods have dropped or are in the process of dropping their leaves.

Gartner said unseasonably warm days and nights this week could push back the peak of fall foliage to Oct. 18, but shouldn’t ruin the show.

"What we really want is cool nights, sunny days and no hard rain," she said. "The hard rain will bring down the leaves before they have a chance to do their thing."

According to the state Department of Conservation, good routes for fall colors in Central Missouri include Interstate 70 from Montgomery County to Saline County, Highway 54 from New Bloomfield to Camdenton, Highway 63 from Ashland to Rolla, Highway 50 from Rosebud to Centertown, Highway 87 north of Boonville, Highway 179 south of Wooldridge, Route C west of Jefferson City, Highway 94 east of Jefferson City, Highway 19 south of New Florence and almost any road in Camden, Miller, Maries, Osage and Gasconade counties.

Missouri Department of Conservation

For fall color updates as the season progresses, visit http://www.missouriconservation.org/nathis/seasons/fall/. Source: Steve Pallardy, 573-882-3548

Sara Agnew
Senior Information Specialist
573-882-6843