CEDAR CITY — As the temperatures cool and the nights grow longer, trees growing on Southern Utah’s mountain hills, meadows and lava flows begin to change – spotted with gold, yellow and burnt orange. Autumn is coming.
The “most numerous and common” species of deciduous tree seen at Southern Utah’s higher elevations is the quaking aspen, Dr. Jacqualine Grant, an associate professor in Southern Utah University’s Geosciences department said. Aspen leaves sometimes turn red or orange in the fall but are typically yellow.
“So when you go up in the hills and you see that beautiful gold, that is mostly the aspen trees,” she said.
The trees are clonal, which means multiple sprouts can grow from the same root system and a group of aspens could be a “single organism that shares the same genetics,” Grant said. Because of this, they tend to change color in patches.
“If you happen to notice as you’re driving through the mountains that there’s a patch of one kind of yellow and then another large patch of a slightly different kind of yellow, you might be looking at two different genetic clones of the same Aspen species,” Grant said.
While some aspens turn red, the trees that are more “known” to do so are maples and oaks, which are smaller than the aspens and typically seen at lower elevations, Grant said.
Sunlight, temperature and cloud cover are all factors that affect which chemicals are expressed by the trees. If temperatures remain above freezing, leaves are more likely to be red, but an early frost will weaken the color. If it’s been rainy or overcast, “like we’ve seen this fall,” Grant said the intensity of fall colors would increase.
Chlorophyll causes leaves to appear green, while carotenoids are responsible for orange, brown and yellow foliage; both are present in leaves during the growing season. According to the United States Forest Service, red leaves result from anthocyanins, which are typically produced in autumn “in response to bright light and excess plant sugars within leaf cells.”
However, whether a tree turns red this autumn will depend on the species and, in the case of aspens, a particular specimen’s genetics, Grant said.
As the nights lengthen, chlorophyll production slows, then stops and eventually all of the chemical present in the leaf is destroyed, leaving behind carotenoids and anthocyanin to express their hues, the Forest Service states.
And the forest bursts with color.
Southern Utah’s drought and how the drought interacts with the monsoon season also impacts fall color, Grant said. Extreme drought early in the season weakens trees, which often don’t recover even after storms.
Late-season droughts can also cause leaves to drop earlier than expected. Early leaf shedding is a response to the trees not having enough water to prepare for and survive the winter.
“We’ve had such a wet summer that I don’t expect the leaf-peeping season to be shortened by the early summer dryness,” Grant said. “Fall temperatures will probably be the biggest driver of the length of this season’s leaf-peeping time.”
Viewers interested in peeping leaves mid to late-Sept. can do so throughout higher-elevation Southern Utah. To immerse in golden-hued aspens, Grant suggests traveling down Second Left Hand Canyon Road and Right Hand Canyon Road to Kolob Reservoir.
“But all throughout the Dixie National Forest, there’s really good places to see the yellows of the Aspen’s up at high elevation,” she said.
Grant also recommends driving State Route 20 from Panguitch to Beaver to see “shrubby” maples and oaks, as well as fall flowers like purple beeplants, to “get nice contrast” between purple blooms and orange and red leaves.
To learn more about leaf-peeping in Iron, Garfield and Kane Counties this fall, view the Fall Color Report, shared on Visit Cedar City – Brian Head’s website.
The page is updated weekly with the percentage of leaf change based on elevation. Additionally, the site offers directions for fall viewing from Parowan Canyon, through Brian Head, Cedar Breaks and Duck Creek, with suggested sights and activities.
Photo Gallery
Yellow aspens, Webster Flat, Utah, Oct. 10, 2021 | Photo by Alysha Lundgren, Cedar City News A bench surrounded by fallen, yellow leaves, Brian Head, Utah, Sept 23, 2018 | Photo by Alysha Lundgren, Cedar City News A red maple leaf, Parowan Canyon, Utah, October 20, 2020 | Photo by Alysha Lundgren, Cedar City News Golden-hued aspens at Navajo Lake, Utah, Sept. 27, 2020 | Photo by Alysha Lundgren, Cedar City News Fall leaves in Second Left Hand Canyon, Oct. 6, 2021 | Photo by Alysha Lundgren, Cedar City News Red aspens at Aspen Mirror Lake, Duck Creek, Utah, Oct. 7, 2021 | Photo by Alysha Lundgren, Cedar City News Red maple leaves, Kolob Canyons, Utah, Oct. 25, 2020 | Photo by Alysha Lundgren, Cedar City News Single yellow leaf on a green tree, Duck Creek, Utah, Sept. 9, 2022 | Photo by Alysha Lundgren, Cedar City News Aspens changing color, State Route 143, Utah, Sept. 10, 2022 | Photo by Alysha Lundgren, Cedar City News
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