Mid-October should, technically, be the peak of colorful fall foliage in the Kansas City area. But compared to previous autumn, the metro area has looked a little muted this year.
After especially warm conditions this summer and fall, a lot of trees have been changing out their summer green to dull yellows and browns, rather than the vibrant reds, oranges and maroons we’ve come to expect.
Hank Stelzer, a professor of forestry at the University of Missouri School of Natural Resources, says that harsh, dry conditions like Missouri and Kansas have been experiencing can change trees’ metabolic processes on a molecular level.
“September was our driest on record, at least here in mid-Missouri,” Stelzer said. “So the food wasn't produced, the sugars, the pigments weren't produced. And then we had a hot September and, really until just recently, relatively warm days and warm nights. So the pigments maybe aren't gonna be as spectacular as they have in years past.”
Strained by drought, some trees began to change colors as early as August — but not in a particularly attractive way.
“You'll tend to see what we call scorch,” said Stelzer. “You might have a green leaf, but around the margins of the, of the edges there, of the leaves, they just look like somebody took a torch to 'em… that's usually a really good indication that the trees are really stressed.”
As for the sporadic but hard rainfall that Kansas City is seeing this week? The water won’t help much, and could possibly hurt the trees even more.
“Not only are you first flooding them, but then [that’s] followed by a dry period that’s too long for them, followed by maybe another flooding period,” said Mike Fiaoni, a forester at the Missouri Department of Conservation.
A forest of many colors
According to Stelzer, the forests of Missouri have more than 150 different types of hardwoods. Kansas has 166 types of trees, shrubs and woody vines, many of which it shares with its neighboring state.
Each species has its own innate underlying leaf color. White oaks tend to turn a deep wine color while dogwoods turn purple. Red maples and sugar maples turn a deep red, along with black gums and northern red oaks. Meanwhile, hickories and ironwoods turn yellow.
The tree species in our region that often “pops” the most, Stelzer says, is probably the Freeman maple, a natural hybrid of a red maple and a silver maple. Its jagged, five-lobed leaves turn a bright crimson.
Different species of trees also tend to change colors at different times during the fall, and their peaks stagger out over six to eight weeks, according to the Missouri Department of Conservation’s website.
Sumac and sassafras are some of the first to change in mid-September, with black gum and dogwood following at the end of the month. Maples, oaks and hickories peak in mid-October, and by November, trees should be dropping their leaves and fading color.
Shortening days and dropping temperatures help cue trees to stop producing chlorophyll in their leaves. Chlorophyll, the compound that produces sugars from sunlight and gives the leaves their green color, breaks down, revealing colorful compounds beneath.
“The yellows and the oranges, the carotenoids, like in your carrots… start showing through,” said Stelzer.
Carotenoids are present in green leaves, but are just obscured by the chlorophyll. However, anthocyanins, the compounds that make leaves a red or purple color, are produced in the fall.
Clear sunny days cause leaves to produce more anthocyanins, and cold nights slow the movement of pigments, sugars and other nutrients out of the leaves and into the rest of the tree. But cloudy days and warm nights — which Kansas City experienced a lot of in September — mean that leaves produce fewer anthocyanins and can't hold onto them as well.
That means less color left behind for the leaf to show off.
Stressed out trees
Anne Wildeboor, a horticulturist at the Overland Park Arboretum, said that their trees are holding onto their leaves better and showing brighter colors than she had expected, given the circumstances.
Stelzer added that the red maples and sugar maples have proven surprisingly bright this autumn.
Wildeboor did note, however, that even some mature evergreens are struggling in ways that she had never seen before. She noted that evergreen needles began turning yellow, which she called “a big concern.”
A long drought puts stress on trees, but they’re resilient enough to survive in the short term. It’s when dry seasons stack up year after year that the problem becomes apparent.
“Periods of drought are becoming longer and more frequent,” Wildeboor says.
Even mature, established trees that she wouldn’t have worried about before are becoming weaker and more vulnerable.
“We saw a lot of issues with trees this year where the stress of last summer did not present itself until it went through the winter… because the winter was pretty dry as well,” she said.
As climatologists have warned, over and over again, climate change is only making this situation worse. And we’ll see the effects reflected in our trees.
Stelzer, at the University of Missouri, says he waters the trees on his property when there’s less than an inch of rainfall per week, because prolonged drought and heat can seriously harm their root systems and make it harder for them to survive the winter.
“My neighbors thought I was crazy, watering my trees this year,” Stelzer commented. “I said, ‘Well, I was making sure that I wasn't gonna lose those trees who have been stressed out.’”
After all, it’s relatively easy to replace grass -- and a whole lot harder to replace a tree that’s been living for 20 years.
Where to see the best fall colors in Kansas City
Despite the weather conditions, Kansas City still has plenty of trees to admire. You can find some of the region’s best places to take in the fall foliage in this story from KCUR’s Adventure! Newsletter — especially Cliff Drive within Kessler Park.
Other great tree-peeping places in the city include Loose Park, Swope Park, Gillham Park, Maple Woods Natural Area and the lawn of the Nelson-Atkins Museum of Art.
Kansas leaf-lovers can get their fill at Black Hoof Park, Mill Creek Streamway Park, Indian Creek Trail, and the Overland Park Arboretum & Botanical Gardens.
