Forage 2025 | Managing Invasive Grasses: Yellow Bluestem and Cheatgrass Control
returning. The area surrounding the plot is cheatgrass. Photo courtesy of Nevin Lawrence.
Invasive grasses can quickly take over rangeland and diminish forage quality. Keeping rangeland healthy by not overgrazing and keeping a tight canopy of native plants are ways to keep invasive weeds like yellow bluestem and cheatgrass out of rangelands.
According to Rodney Voss, a Rangeland Management Specialist with the Natural Resources Conservation Service in South Dakota, “prevention is key, so managing for healthy rangeland on the front end is really important.”
Being able to detect and manage existing stands is also important to reduce the spread of invasive grasses.
Yellow bluestem is a perennial bunch grass that is a prolific seed producer. It primarily disperses through seeds but can spread by rhizomes or stolons if mowed or cut for hay. It can be challenging to identify early on in the growing season; however, it will not be as dark green as the surrounding grasses. In late August, the grass develops a purplish-silver inflorescence. This grass has distinctive purplish brown colored nodes.
Brian Mealor, Director of the Institute for Managing Annual Grasses Invading Natural Ecosystems at the University of Wyoming, and Nevin Lawrence, Weed Scientist at the University of Nebraska-Lincoln Panhandle Research, Extension and Education Center, both described cheatgrass.
Cheatgrass is an invasive annual. It is a cool season grass, so it will germinate in the fall and go to seed earlier. The most common way to identify cheatgrass is by its seed head which turns bright red in late spring. The plant as a whole will turn brown while the surrounding grasses are still green.
For different reasons, yellow bluestem and cheatgrass will take over sites and negatively impact forage quality.
Yellow bluestem is a low-quality forage, and livestock do not prefer it. This can create an issue of overgrazing the other forage.
“The ironic part is one of the reasons it was brought to this country was for forage production and erosion control in the early 1900s in Texas,” Voss said.
This grass can form sod and chokes out native vegetation. It also puts out biochemicals that prevent seed growth and plant development of other species which leads to a monoculture of yellow bluestem.
While yellow bluestem will choke out native forage, cheatgrass will outcompete native forage with its early start.
Cheatgrass makes a good early forage until it seeds out. At that point, livestock will not graze it. It used to be marketed as a miracle 100-day forage.
Desirable plants are limited in productivity by cheatgrass as cheatgrass gets to important resources like water first. This out-competition can get progressively worse year after year if conditions are right.
“What is left is a shifting balance away from nutritious, diverse, native plant communities that hold their forage value later into the season toward dominance by cheatgrass or the other invasive annuals,” Mealor said. “Then forage quality dramatically reduces for most of the grazing season.”
Since cheatgrass is dead before late summer, it poses a significant fire hazard.
“It can contribute to having increased fire cycles and fire intensity,” Lawrence said. “When it happens those fires are not going to hurt the cheatgrass, but it is going to hurt the more desirable plants that we have.”
Every time there is a fire, the cheatgrass will come back more plentiful.
Managing these invasive species is not an easy or a one-and-done solution. Overall maintenance of healthy rangeland can help prevent these weeds from taking over. However, if conditions are right, these weeds will take over anyway. There are options to manage these invasive grasses.
Yellow bluestem is easier to manage while the stands are small.
“It does not take very long for it to establish itself,” Voss said.
Voss advises caution when driving from areas with Yellow Bluestem to areas without it as this creates the movement needed for the seeds to spread.
Chemicals alone or in combination with prescribed fire can help alleviate the problem, but it will require multiple treatments per year. It is important to always follow chemical labels.
The best time to use prescribed fire on yellow bluestem is when the plant is in the boot stage, which is when the seed head is beginning to develop. Prescribed fire should be followed up with a chemical treatment.
For cheatgrass, grazing and herbicides are the most effective ways to alleviate infestations.
“What management looks like is trying to keep it from spreading and getting it to not increase in abundance and guarding areas of rangeland that have little to no cheatgrass and areas that are most productive,” Lawrence said.
Putting grazing pressure on cheatgrass early before it seeds out can help reduce seed production and manage the cheatgrass population.
Rejuvra, or Indaziflam, is a pre-emergent herbicide that is very effective in managing cheatgrass as it does not affect perennial forage and has about two years of effectiveness if applied at the right time and rate.
“Rejuvra is a very effective tool, especially on sites that are impacted by annual grasses where there are still desirable perennial plants established,” Mealor said. “We can shift the balance from cheatgrass-dominated sites with a suppressed perennial community back to a perennial-dominated site.”
When applied in the spring, Rejuvra will not need to be paired with other herbicides, but if it is applied in the fall or late winter, a post-emergent herbicide would be beneficial. Some post-emergent herbicides that can be paired with Rejuvra are Rimsulfuron or Plateau.
Rejuvra targets more than just cheatgrass and is active in the soil for two to three years, so it is advisable to make sure desirable perennial plants are established before application to avoid having bare ground.
“Rejuvra is expensive,” Lawrence said, “but luckily there are a lot of programs with the Natural Resources Conservation Service and sometimes county and state organizations that help cost-share that herbicide.”
These programs can sometimes require grazing restrictions to reduce the risk of overgrazing the remaining perennials.
Ultimately, doing nothing about invasive grasses is only going to continue to degrade forage production and long-term quality.
“There has been this big shift of potentially millions of acres per year converting across the Western United States to sites dominated by annual grasses,” Mealor said.
Extension agencies, county weed and pest districts and invasivegrasses.com can provide information and resources to ranchers who want to help preserve quality, native forage.
