A controversial herbicide project at Red Hill has now been paused, resumed and paused again by Boulder County commissioners.
Opponents say the back-and-forth over the past two months has deepened concerns about public trust around a high-profile issue they believe still warrants open public debate. County officials, however, say the project was already approved under an existing weed management plan.
That tension has played out over a series of decisions since early December. On Dec. 9, county commissioners paused plans for aerial drone spraying of herbicide across open space at Red Hill to control invasive cheatgrass. The decision followed strong backlash from residents over health concerns, ecological impacts and the pace of the project.
Six weeks later, on Jan. 21, commissioners appeared to direct staff to move forward with the herbicide project during an administrative meeting that drew little public attention. The decision caught many critics off guard and created confusion about what, exactly, had been decided, renewing concerns about transparency.
The December pause was supported by Commissioners Marta Loachamin and Ashley Stolzmann, with Commissioner Claire Levy opposed. That decision came during a public business meeting with advance notice and a recorded livestream, following a public comment session on Dec. 4.
By contrast, the Jan. 21 direction to staff took place during an unrecorded administrative meeting without advance public comment. Loachamin appeared to reverse her earlier position and joined Levy in moving the project forward. Opponents quickly criticized the process, though commissioners said the decision followed county procedures.
Stolzmann questioned the commissioners’ approach. “I think it’s poor judgment of the board to enact a moratorium in a public forum and then repeal it in a less obvious forum,” she told Boulder Reporting Lab at the time.
Commissioners revisited the issue again at a Feb. 3 business meeting and paused the project again while they await the county’s annual weed management update later this month. No final decision has been made.
While Ryan Madson, managing director of Drylands Agroecology Research, or DAR, opposes the project, he said he is unsure what another pause would accomplish. “We know that Boulder County management is essentially just trying to make the case for the spray,” he said. “So without further community input, it’s unclear if that’ll be a positive change or not.” DAR sits downwind of the proposed spray area.
County officials argue the herbicide indaziflam is the most effective tool available to control invasive cheatgrass at Red Hill, which they say reduces water resources for local ecosystems and increases wildfire risk. Residents and researchers who oppose the project question both the need for chemical treatment and the evidence supporting large-scale aerial spraying.
What is Red Hill, and why cheatgrass matters
The Red Hill open space area, located just west of U.S. 36 between Boulder and Lyons, includes parts of Heil Valley Ranch and other properties. Where the plains meet the foothills, the area has been identified as a biodiversity hotspot, with about 350 documented species, making it a priority for county conservation efforts.
The county wants to spray the herbicide indaziflam on about 800 acres of land near U.S. 36. Drones would fly low over the area to apply the chemical. County officials say buffers and timing restrictions were added to reduce runoff and unintended exposure.
The optimal window to apply indaziflam ends in late February, according to county spokesperson Gloria Handyside, and spraying cannot occur when snow is on the ground.
Cheatgrass, a winter annual invasive grass native to Eurasia, has spread widely across the western United States. In Colorado, it does not dominate landscapes as aggressively as it does in the Great Basin, according to Colorado Parks and Wildlife grasslands habitat coordinator Trent Verquer. Still, cheatgrass draws up water early in the growing season, depriving native plants of moisture and nutrients.
“Regardless of the amount of precipitation that we get,” Verquer said, “in an area with cheatgrass there’s less nutrients and moisture available for other plant species.”
County officials cite those impacts as justification for chemical intervention. “We’re just trying to meet our land stewardship goals for these sites,” said Boulder County weed coordinator Joe Swanson, adding that the goal is to prevent long-term ecological degradation and support native plant communities.
Some researchers, however, question whether herbicide use is necessary or effective under Colorado’s conditions.
Tim Seastedt, director of CU Boulder’s Spruce Gulch Wildlife and Research Preserve in the foothills, says his research shows that cheatgrass, left alone without herbicide or grazing, will naturally decrease over time. Seastedt believes the plant is better adapted for the Great Basin’s water cycle than Colorado’s.
“It still can exploit disturbances, but it can’t persist as a dominant, threatening species,” he said.
Fraying public trust
Distrust of the county’s herbicide practices predates Red Hill. The advocacy group Save Our St. Vrain Valley has accused the county of applying herbicide without proper documentation or public engagement since 2014 and has filed a complaint with the Colorado Department of Agriculture, which remains under investigation.
Local land restoration advocate Christel Markevich said county residents were previously successful in banning the herbicide glyphosate. In recent years, advocacy efforts shifted toward opposing aerial spraying and, more recently, indaziflam, which she said has produced inconsistent results.
“The concern is that spraying this chemical can bring a lot of damage,” Markevich said. “There’s a lot of uncertainty.”
Concerns about the public process intensified after the Jan. 21 administrative meeting, which critics said lacked adequate notice and public visibility. Commissioners Ashley Stolzmann and Claire Levy said the action was administrative rather than legislative and therefore did not require a public hearing.
County officials have said the Red Hill spraying was already approved under the county’s Integrated Weed Management Plan, adopted in November 2024 after public review, and will remain in effect until its next scheduled update in 2027.
“Red Hill was exactly in accordance with what we adopted,” Levy said last month. At the Feb. 3 meeting, she said she was concerned about missing the narrow February spray window.
Stolzmann said she supports addressing invasive species but remains frustrated that alternatives have not been more fully explored.
Why herbicide, why now?
Indaziflam entered the market in 2020 and has become Colorado Parks and Wildlife’s most effective tool for combating cheatgrass, according to Verquer. He said that even a single low dose can suppress cheatgrass growth for years.
“It’s the only tool in my career that I’ve got faith in that we can use to actually get ahead of the cheatgrass,” Verquer said.
Other management options exist, each with tradeoffs. Grazing has been ruled out at Red Hill to protect vulnerable bighorn sheep populations, while manual removal was deemed impractical due to steep terrain and safety concerns. Those constraints led the county to select drone-based application.
Opponents point out that indaziflam remains in soil and can prevent plants from taking hold, raising concerns about harm to native species and soil health. Seastedt of CU Boulder said its effects on soil invertebrates have not been fully studied. (Swanson, with the county, said that when applied at the right time, many native seeds are deep enough in the soil to be unaffected, and county research suggests native plants rebound faster after application.)
Markevich also questioned the scale of the proposed spraying, citing studies that suggest indaziflam could damage human DNA and raising concerns about risks tied to drone malfunctions, including fire ignition. Other residents said earlier, smaller-scale trials may not reliably predict outcomes at Red Hill.
County officials counter that, beyond ecological impacts, the project is also intended to reduce wildfire risk. They describe wildfire mitigation as an additional benefit of the spraying, noting that cheatgrass ignites easily because of its fine structure and low moisture content.
“If it’s 95 to 100 mile-per-hour wind, that’s not going to slow much of anything down,” Swanson said. “But in normal conditions, that would have a fairly dramatic impact.”
Seastedt disputes the framing of cheatgrass as uniquely dangerous, as it can be matted down by snow, limiting its ability to spread fires.
“To argue as a generality that this plant is more problematic than perennial grasses is simply false,” he said.
Correction, February 4, 2026 11:27 am: An earlier version of this story misstated the public comment process leading up to the Boulder County commissioners' Dec. 9, 2025 decision. There was no public comment during the Dec. 9 business meeting itself. Public comment occurred at a Dec. 4 meeting, and that input informed the Dec. 9 vote.
Take note: indaziflam comes from Bayer Environmental Sciences (now spun off to another company in one of those dizzying corporate catch-me-if-you-can games.) Bayer bought the chemical company Monsanto in 2018, along with all its products – Roundup being one of the most familiar – but retired the name Monsanto. In the long and complex history of chemicals used in agriculture, Monsanto emerged as the most notorious company for introducing products that harm the environment. At one point many activists referred to Monsanto as “MonSatan” because the company appeared to be pure evil driven by greed. Though Bayer bought the company and erased the name, its dark shadow lives on. The promises made by chemical agriculture are lies.
Spraying herbicide is the laziest and least effect means of weed control, so I’d love to hear the reasoning for this application from an credentialed scientist. Because although not well credited here, Tim Seastedt is distinguished and universally-respected senior researcher in grassland ecology among holding PhD. Furthermore, there are three proven biocontrol methods for using bacteria
(Pseudomonas fluorescens D7, Pyrenophora semeniperda, Ustilago bullata) that have not even been discussed or explored either.
Let’s not frame the question as “to spray or not to spray?”
But rather:
What is the role of vegetation and disturbance regimes in this landscape, and how might we shape land stewardship with humility toward complex ecological rhythms?
This shift moves the focus from control to co-learning with system dynamics, including seasonal water flows, fire regimes, native plant succession, soil life, wildlife patterns, and human use.
________________________________________
Let’s Center multi-temporal perspectives
This project has a narrow February spray window. But what about 10- and 50-year horizons? How will plant communities, soil organisms, pollinators, and human communities experience the outcomes? What does “success” look like then?
Rather than acting on the fear of fire or invasive dominance alone, a planetary limits frame invites us to stay with gradients of uncertainty as a source of insight.
How about Redistributing epistemic authority?
Instead of privileging (only) government land-stewardship plans or (only) scientific publications, relational inquiry would:
• weave in narratives of farmers closest to the land; DAR, etc
• integrate Indigenous land-care practices appropriate to these lands;
• hold experimental and place-based knowledge as legible alongside institutional knowledge.
Lets design space for co-inquiry — shared field observations, multi-species monitoring, and collaborative decision mechanisms — before deploying interventions that echo for years.
“What does responsible effectiveness look like when we consider not only what works now, but what we are asking the land—and future communities—to live with?”