Cheatgrass (Bromus tectorum) is a highly invasive annual grass that dominates millions of acres across North America, especially in the western United States. Originally introduced from Eurasia, this species aggressively outcompetes native vegetation by taking advantage of early-season moisture and nutrients. The most damaging consequence of a cheatgrass invasion is the drastic increase in wildfire risk, as the plant dries out early in the season, providing a continuous, fine fuel layer that promotes frequent and intense fires. Successful control requires an integrated, multi-year management plan that specifically targets the plant’s unique life cycle.
Understanding the Cheatgrass Life Cycle
Timing is the most important factor for any cheatgrass control strategy due to its compressed and opportunistic life cycle. As a winter annual, cheatgrass seeds typically germinate in the late fall or early winter once moisture is available, though they can also germinate in the spring. After germination, the plant develops a robust root system throughout the cold winter months, giving it a significant head start over native perennial grasses.
The plant resumes rapid above-ground growth very early in the spring, accessing soil moisture and nutrients before most native species have broken dormancy. Heading and flowering occur quickly in the late spring, often by late April or early May, and viable seeds are produced by mid to late June. Once the seeds mature, the plant quickly dies, turning a characteristic reddish-purple and then tan, creating a highly flammable landscape. The critical window for control is when the plant is small, green, and actively growing, but has not yet produced viable seeds.
Non-Chemical Control Methods
For controlling smaller infestations or in areas where chemical use is restricted, physical and biological methods can be effective if executed precisely. Mowing can prevent seed production, but a single pass is often ineffective because the plant regrows and produces new seed heads below the cutting height. Mowing must be repeated every two to three weeks until the flowering stage is complete to ensure no seeds mature.
Tillage or plowing is a viable option in agricultural settings, but it can cause soil disturbance that cheatgrass thrives in. To prevent germination, existing seeds must be buried at least three inches deep, and this process often requires repetition to eliminate newly emerged seedlings. For very small, localized patches, hand pulling is practical, provided it is done before the soft seed heads form. Any pulled plants that have already formed seeds must be immediately bagged and removed from the site to avoid scattering them.
Targeted livestock grazing, often using sheep or goats, can deplete the plant’s energy reserves. Grazing must be scheduled in the early spring while the cheatgrass is still green and palatable, and before the awns and seeds develop. For effective control, the area should be grazed intensely twice in the spring, with the second pass occurring about three weeks after the first. Prescribed burning is a high-risk method that can reduce the current year’s biomass if timed just before seed maturity. However, burning often stimulates a massive flush of new cheatgrass seedlings and should only be conducted as a preparatory step immediately followed by reseeding and aggressive follow-up treatments.
Herbicide Application Strategies
Chemical control is highly effective but requires distinguishing between the two main types of herbicides and correctly timing their application. Pre-emergent herbicides create a chemical barrier in the topsoil, preventing seeds from germinating and establishing roots. Since cheatgrass germinates in the fall, these herbicides must be applied in the late summer or early fall, before seasonal precipitation triggers germination.
Common active ingredients used in pre-emergent control include imazapic and indaziflam. Imazapic is often used at low rates because it provides selectivity, sparing desirable perennial grasses while targeting annual weeds. Indaziflam provides longer-lasting control of cheatgrass. Both can provide control lasting beyond a single season.
Post-emergent herbicides are absorbed by the plant foliage and are effective against cheatgrass that has already emerged. Systemic treatments, such as glyphosate, are best applied in the fall, winter, or very early spring when young plants are actively growing. Glyphosate is non-selective, meaning it will kill any green plant it contacts, and is typically reserved for sites with few desirable native plants or as a pre-seeding treatment. Labels provide instructions on proper application rates, environmental restrictions, and the need for a surfactant, which improves effectiveness.
Long-Term Prevention and Land Restoration
Eradicating existing cheatgrass is only the first step; long-term success depends on restoring the land to prevent re-invasion. Cheatgrass thrives in disturbed, open ground, so the most durable defense is establishing a dense, competitive cover of perennial vegetation. Seeding the treated area with aggressive, locally adapted perennial grasses, such as native wheatgrasses or other cool-season species, is necessary to occupy the space cheatgrass would otherwise exploit.
Perennial grasses possess deep, fibrous root systems that utilize soil moisture and nutrients more efficiently than the shallow-rooted annual cheatgrass. In areas using selective pre-emergent herbicides like imazapic, specific warm-season grasses such as buffalograss or blue grama can be seeded simultaneously due to their higher chemical tolerance. Minimizing soil disturbance is also an ongoing management practice, which involves reducing unnecessary vehicle traffic and limiting tillage.
A single season of control will not eliminate the problem, as cheatgrass seeds can remain viable in the soil seed bank for two to three years. Therefore, a successful plan requires a multi-year commitment involving consistent monitoring of the treated areas. Follow-up spot treatments, using hand pulling or targeted herbicide application, are essential for eliminating new outbreaks and preventing the re-establishment of a large seed-producing population.