The Morton Arboretum's Sharon Yiesla said while the later part of next month will see the peak of fall foliage vibrancy, the wide variety of specimens at the arboretum offers a longer viewing season from early changers to latecomers. (photo provided)
What can we expect for this fall's color?
Predicting how colorful the autumn's tree color display will be is not an exact science, according to the Morton Arboretum plant knowledge specialist Sharon Yiesla.
"The thing with fall color is it's usually multiple things that contribute to fall colors," she said. "I think there will be good fall color, We just can't say how brilliant or how dazzling it will be."
Specifically those factors are leaf pigments, length of the nights and weather. As many of us may remember from grade school science class, during the growing season for trees, chlorophyll is continually being produced and broken down, making leaves appear green. As night length increases this time of year, chlorophyll production slows down and is ultimately destroyed, allowing the carotenoids and anthocyanin pigments in the leaf to have their moment.
That process happens earlier in species like the shrub-like sumac and the honey locust tree, Yiesla said.
"The sumac starts to turn red, and the honey locust gives us bright gold. We're just at the very beginning of this right now," Yiesla said
But there are also varieties that have little to show.
"Some of the European trees may get a little yellow-green at best. They're not genetically able to get good fall color," she explained.
Dry conditions and cooler weather tends to accelerate the leaf-changing season. Yiesla acknowledged the recent dry spell could have a slight impact but pointed out the year overall has been relatively solid in terms of precipitation.
"Luckily we haven't been dry all year. It's better than if we had a year that was totally dry," she said.
Yiesla said a stretch of bright, sunny days and cool, crisp - but not freezing - nights seem to yield the most spectacular displays. She said setting expectations based on northern regions already seeing the colors change is not reliable because of different weather patterns.
"What's happening in Wisconsin may be very different from what's happening here," she said.
Yiesla does not expect to see much in the way of changing colors in these parts until next month for most tree varieties.
"I think we're not going to see the peak until October," she predicted.
Trees that are showing signs of browning due to the recent dryness should be given thorough soakings.
"A good watering should help a flagging tree bounce back," she said.
Yiesla noted the fact of very premature foliage change among some trees.
"We did see some trees that got color early this year," Yiesla revealed. "Some of the maples actually colored up a little bit in, like, early summer. They got a blush of color early in the summer and they've kind of stayed that way."
Rain will help forestall the leaves' eventual descent ground-ward, she said, advising a visit to the arboretum for comprehensive tour de foliage by way of a leisurely walk or drive through the grounds.
"I love fall. The colors are tremendous. It's a kaleidoscope of color," she said. "I enjoy autumn as much as everybody else does"
- by Ken Knutson
