COLUMBIA — Ash trees have started to tout their yellow and purple pigments. The yellow leaves of the black walnuts have filtered in and the red maples are starting to blush.
As we near the end of a week with ideal fall color weather, leaves on mid-Missouri trees have already begun to change colors and local foresters are optimistic that Mother Nature's fall color palette will be exceptional.
"This natural phenomenon is not necessarily quantifiable, and it's really weather-dependent more than anything," said Tim French, the Missouri Department of Conservation's forestry regional supervisor. French said this season's display promises to be "above-average."
Fall foliage is primarily tied to temperature, with precipitation as a supplementary factor. For best color, the weather needs to be cool and sunny.
"Predicting fall color requires that you predict the weather," Steve Pallardy, an MU forestry professor, said. Ideal weather would be sunny with temperature lows near 40 degrees at night and highs in the upper 50s and lower 60s during the day, Pallardy said.
The National Weather Service forecasts a week matching perfectly with the prescribed climate for fall foliage. Today and Friday should have highs in the upper 60s and lows in the high 40s.
“If we get those kinds of conditions right then, then we tend to have really good fall color,” Pallardy said. “It has the potential to be good. The long-range forecast is for temperatures that are probably reasonably good for fall color especially for reds and purples.”
But, the overall weather pattern has been shaping the fall foliage outlook since spring. Adequate rainfall is crucial to good foliage.
"We've had higher than normal moisture so the trees are in pretty good shape," French said.
According to the National Weather Service, Columbia had received 51.55 inches of precipitation this year as of Wednesday. This is 20.28 inches above the normal total and almost 30 inches more than last year.
Following cooler temperatures, fall foliage starts north and moves south through the country. In mid-Missouri, the peak of fall foliage is typically during the second or third week of October. However, sometimes this period can stretch to the end of October.
Pallardy described the cycle where the leaves of certain tree species change at different rates. But once leaves begin to lose their green, the new color will peak in a few days.
“For any one species it’s going to be a matter of days,” Pallardy said. "But since there are a variety of species turning, and they don’t all turn at the same time, there’s sort of a wave that comes" during the second, third and sometimes the last week of October.
However, Pallardy cautions that sometimes the first trees to show color are distressed. He cited a particular tree on West Broadway: a sugar maple in a cemetery near the southwest corner of Broadway and Providence is already well into its color change and has lost most of its leaves. Pallardy speculates that the particular tree is prematurely losing its color as a result of low-oxygen soil.
The peak for foliage in some plants has already come and gone. According to the Department of Conservation, sassafras, sumac and Virginia creeper typically begin to change by mid-September. By the end of September, black gum, bittersweet and dogwood start to show to their color, too.
As the weather begins to get cooler and days become shorter, leaves begin to slow down making chlorophyll — the source of food for the plant. Chlorophyll gives leaves their green pigment. As the remaining chlorophyll begins to break down, the green color starts to fade.
As the green pigments fade out, other color pigments phase in. Whether a leaf becomes orange, red or purple depends on the tree and the plant's chemical pigments, Pallardy said.
For Pallardy, memorable fall foliage usually consists of high levels of purple and red pigment.
Pallardy explained that most trees have high amounts of carotenoids, the yellow pigment, but anthocynins, the red/purple pigments, synthesize better with abundant rain.
With its ability to be red, orange, yellow and even a mixture of all three, the sugar maple is a popular leaf to catch before it falls. "They usually have the most striking colors," French said.
Pallardy, who favors the sugar maple for fall foliage above all the other trees, suggests checking out the bluffs along the Missouri River — especially on Route 94 — as a prime spot to see the fall color.
But stay tuned: Mother Nature will have the final say in this year’s fall foliage. “The weather has to stay clear and cool, but not freezing,” said Pallardy, dispelling an old myth. “So the old tale about Jack Frost and his paint pots is not accurate.”