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In recent decades, ecologists and land managers across the American West have treated cheatgrass as a threat.��

On lands where the scraggly plant, which produces seeds that burrow into socks and shoelaces, thrives, native plants seem to suffer. When the organism wilts and dries up in summer, it can become ready fuel for wildfires in parts of the country already struggling with destructive blazes.

But a new�� published in Restoration Ecology by researchers at the ��ñ���� suggests that on Colorado’s Front Range, cheatgrass may not be invasive after all. The authors contend that large-scale herbicide spraying is unnecessary and could cause more harm than the weed itself.

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Tim Seastedt at Spruce Gulch. (Credit: Gabe Allen/����)

The study comes as Boulder County land managers

“We found that managing cheatgrass is more complex than we once thought,” said��Tim Seastedt, an emeritus professor in the Department of Ecology and Evolutionary Biology, as he pointed to the small patches of cheatgrass at the��Spruce Gulch Wildlife and Research Reserve just outside of Boulder. “The traits that make the plant successful in some climates aren't nearly as effective in places like ours. Our data suggests that the Front Range can cure itself with regard to cheatgrass.”��

Seastedt is the director of the Spruce Gulch reserve, a 476-acre natural area managed by ��ñ����’s Institute of Arctic and Alpine Research (INSTAAR). Before 2006, ranching and grazing activity on the land removed a substaintial percentage of its native plants. Cheatgrass, a fast-growing species introduced from Europe in the 1800s, seized the opportunity and spread rapidly. ��

Scientists have estimated that cheatgrass accounted for 60% of the vegetation cover at Spruce Gulch in 2011.����

Front Range vs. the Great Basin

Unlike most native plants in the western United States, which can live for many years, cheatgrass is an annual plant. It germinates in late fall to early spring, and by summer has��dried up, dropping new seeds onto the ground. This rapid lifecycle allows the organism to outcompete native grasses for resources, especially in disturbed ecosystems.��

In the Great Basin, a 200,000-square-mile region spanning much of Nevada and the surrounding states to the west of Colorado, research has shown that invasive annual grasses, particularly cheatgrass, have significantly displaced native plants, and their extent has reportedly�� since the 1990s.��

In recent years, land managers across the West have been using an herbicide known as�� to control cheatgrass. The chemical works by preventing grass seeds from germinating and can remain active in soil for up to four years.��

On May 21, officials in Boulder County approved a plan to spray the herbicide across roughly 800 acres of open space in the county west of U.S. 36 this fall or winter using drones. County authorities had paused the plan last December following strong public backlash over concerns about the herbicide’s environmental effects, but are now moving forward after adjusting the treatment area to avoid endangered wildlife habitats and water basins. Jefferson County has also�� indaziflam on its open space lands.��

Seastedt and the review’s co-author,��Robert Brakenridge, a senior research associate at INSTAAR, argue that cheatgrass does not appear to behave like an invasive species on the Front Range.

“Much of what we understand about cheatgrass and the decisions we make to control it is based on studies in the Great Basin region,” Seastedt said. “In their story, cheatgrass is the villain. But that may not be the case here.”��

Brakenridge and Seastedt reviewed all available research, roughly 30 studies in total, on Front Range cheatgrass ecology, as well as on indaziflam’s ecological and safety impacts,��

They found that while cheatgrass can dominate overgrazed land in Colorado temporarily, much as it did in the Great Basin, it fails to outcompete native plants and spread uncontrollably in healthy grassland here.��

For instance, at Spruce Gulch, the team estimated that cheatgrass cover has fallen from 60% to about 10% over the past 15 years without any chemical treatment. They simply let the land recover from overgrazing and ranching.��

The literature also suggested that cheatgrass might not increase fire risk on the Front Range in the same way it did in the Great Basin.��

For instance, while the grass is highly flammable after it dries up in the summer, the Front Range receives about half of its precipitation in spring and summer, meaning much of the surrounding vegetation remains green. These live plants limit cheatgrass’ ability to carry fires across the landscape, unlike more arid regions in the west. ��

“Cheatgrass doesn’t behave like an invasive species here in Colorado in the same way it does in the Great Basin,” Seastedt said. “I’d call it an obnoxious species rather than a noxious one.”

Left: Cheatgrass (in red) accounted for over half of the vegetation cover at Spruce Gulch around 2012. Middle: Cheatgrass cover has fallen to 20% in 2025. Right:��While much of the cheatgrass has not yet dried up and turned red, researchers estimated that its cover has declined to less than 10% this year.(Credit: Tim Seastedt/����)

The risks of herbicide��

On the other hand, past studies the team reviewed have found that indaziflam can kill seeds broadly,��, especially when applied aerially by drone.��

Studies have also reported that the herbicide contains PFAS, perfluoroalkyl and polyfluoroalkyl substances, often called “forever chemicals” for being able to stick around in the environment for a long time. While it remains unclear if PFAS from indaziflam can accumulate in and harm animals and humans, scientists have linked some PFAS to�� like cancers and hormone disruption.��

“We found that here on the Front Range, letting the land restore itself is a better way to control cheatgrass,” Seastedt said. He added that using herbicides to remove the remaining patches of cheatgrass could leave lifeless “brown holes” on the ground, effectively releasing carbon captured by these plants back into the atmosphere and contributing further to climate change.

“It’s exactly the wrong management for climate mitigation,” said Seastedt. “For Colorado, doing nothing is the right approach to cheatgrass management, ecologically and economically.”