Montana Field Guide

PLANTS: An annual bunchgrass. Stems are erect, slender, and grow from 20–50 cm tall, depending upon soil moisture and plant density. Plants are green, but upon maturity turn red-brown. Stems are sparsely hairy (puberulent) below the inflorescence. Sources: Barkworth in Flora of North America (FNA) 2007; Lesica et al. 2012.

LEAVES: Blades are 2–4 mm wide, up to 16cm long, and are softly hair on both sides. Sheaths are often densely and softly retrorsely pubescent to pilose, though sometimes the upper sheaths are glabrous. Ligules are membranous. Sources: Barkworth in FNA 2007; Lesica et al. 2012.

INFLORESCENCE: An open, often nodding panicle of 2–15 cm long. Spikelets are 10–17 mm long with 3 to 6 florets. At maturity spikelets are red-brown to purple. Lemmas are 9–12 mm long, gradually tapered into two narrow teeth. The awn is straight or twisted, 12–20 mm long, and attached to the lemma. Sources: Barkworth in FNA 2007; Lesica et al. 2012.

The common name “Downy Brome” refers to the numerous, fine hairs on its leaves.
The common name “Cheatgrass” comes from pioneering farmers who noticed it reduced their wheat yields, and in feeling cheated named it “cheatgrass”.

See video on Identifying Invasive Annual Grasses in Montana.

Cheatgrass is a winter annual (see REPRODUCTIVE CHARACTERISTICS section).

Montana has 7 species of annual Bromes (Bromus), and only 3 are described below. A technical manual is recommended, such as Manual of Montana Vascular Plants (Lesica et al. 2012).

Cheatgrass – Bromus tectorum, exotic, undesirable, and State-Regulated
* Seedlings have very hairy blades and sheaths.
* Awns are reddish-purple at maturity and easily stick to clothing and fur, and can get into the nostrils and eyes of animals.
* Glumes and lemmas are usually hairy. 1st Glume is 1-veined.
* Lemmas taper into 2 narrow teeth: bodies are 9-12 mm long and awns are greater than 10 mm.

Ripgut Brome - Bromus diandrus, exotic and undesirable
* Lemmas taper into 2 narrow teeth: bodies are 20-35 mm long and awns are greater than 10 mm.
* 1st Glume is 1-veined.

Japanese Brome – Bromus japonica, exotic and undesirable
* Plants tend to grow in more moist sites than does Cheatgrass (but can co-occur).
* Awns are straight or curved outward, less than 10 mm long.
* Glumes and awns not usually hairy
* 1st Glume is 3-to 5-veined.
* Spikelets often several from branch ends.

Cheatgrass grows on overgrazed rangelands, fields, roadsides, waste places, sagebrush steppe, and open, dry understory (Lesica et al. 2012).

DISPERSAL [Adapted from Mosley et al. in Sheley and Petroff 1999]
Cheatgrass has rapidly expanded into native plant communities throughout the intermountain west. This is partially because it was already pre-adapted to this climate. Following its introduction, the west experienced a period of excessive livestock grazing in the late 1800’s, which has reduced the competitiveness of native plants. Following World War I an agricultural depression occurred and many abandoned their dryland homesteads in the Great Basin (Piemeisel 1951). These abandoned cropland fields eventually colonized with Cheatgrass (Piemeisel 1951).

Cheatgrass can thrive in areas that have not been cultivated or grazed by domestic livestock. This is due to its reproductive strategies. Cheatgrass seeds are dispersed short-distances by the wind; its seeds being relatively large and heavy. Meanwhile, animals disperse its seeds long distances because they get caught in hair, feathers, clothing, vehicles and other mechanical equipment, mud attached to hooves and boots, and other vectors. If ingested seeds get transported in feces. Seeds lodged in hay and straw bales that remain dry in storage will remain viable for several years.

VULNERABLE HABITATS [Adapted from Mosley et al. in Sheley and Petroff 1999]
Cheatgrass is found from salt desert shrub communities that receive 15 cm of annual precipitation to high-elevation coniferous forests that receive at least 64 cm of annual precipitation. The most susceptible habitats have deep, loamy soils, south-facing slopes, and 12-22 inches of precipitation that predominantly falls in late winter to early spring.

Cheatgrass grows better in drier environments. It is usually a significant species in early-successional stages. It can be replaced in later-successional stages with perennial grasses. Cheatgrass is less competitive on well-managed foothill sites with perennial grasses. It usually is a minor species in later successional stages on moist sites.

In the drier prairie and steppe habitats, cheatgrass is very competitive and rapidly increases where perennial plants are stressed by drought, fire, or excessive grazing. Large seeded, annual grasses like Cheatgrass also colonize better where biological soils crusts are broken, partially disturbed or absent (Weber, Budel, and Belnap (editors) 2016). Cheatgrass tends to be inhibited where biological soils crusts are intact and healthy (Weber, Budel, and Belnap (editors) 2016; Serpe et al. 2006; Serpe et al. 2008). Colonization occurs in pulses. Cheatgrass populations can surge when growing conditions are favorable, then be unchanged for several years, until another pulse occurs. The critical point of expansion in Cheatgrass populations occurs when they influence the frequency of wildfires.

By changing the fire regime, Cheatgrass changes the composition of plant communities. This has become most noticeable in the sagebrush steppe. Prior to European settlement, intervals without fire lasted 20 to 25 years in the higher elevations of Mountain Big Sagebrush (Artemisia tridentata subspecies vaseyana) and 50 to 100 years in the drier Wyoming Big Sagebrush (Artemisia tridentata subspecies wyomingensis) in the Snake River Plain. However, current fire frequencies burn every 5 years or less in these cheatgrass-invaded habitats. The increased frequency in fire is due to their lifecycle that creates fuel for fires. Relative to perennial grasses, Cheatgrass plants remain green for 6-8 weeks or less. Upon maturity they become brown, dry, and their annual habit results in a higher accumulation of plant litter. Cheatgrass invaded habitats also burn more uniformly, leaving fewer unburned or lower severity burned areas.

The Cheatgrass-fire cycle is self-promoting (Pellant 1990; Peters and Bunting 1994). The native woody shrubs that occupy these habitats do not have reproductive strategies compatible to short-fire frequencies. Thus, winterfat (Krascheninnikovia lanata, Shadscale (Atriplex confertifolia), and Wyoming Big Sagebrush are removed from the system because they cannot survive and reproduce where fire is frequent. Even the more fire-tolerant, sprouting shrubs will eventually be lost because fires occur too frequently. Eventually, all perennial shrubs, grasses, and forbs are removed from the landscape. Cheatgrass establishment thrives because the shallow-rooted grasses more quickly absorb available moisture and nutrients, making it difficult for perennial native vegetation to establish or compete. In such areas where perennial plants area mostly absent and 5-year fire frequencies occur, the Cheatgrass community likely represents a stable community, self-perpetuating.

The annual life cycle of Cheatgrass adds organic matter to the soil surface, which acts as a mulch. This mulch favors the establishment of Cheatgrass seedlings while inhibiting the perennial bunchgrasses. Persistent and heavy mulch covers ground layer organisms, particularly biological soil crusts, eventually killing them (Weber, Budel, and Belnap (editors) 2016).

NUTRIONAL VALUE [Adapted from Mosley et al. in Sheley and Petroff 1999]
Cheatgrass plants are nutritive in the spring. The soft green leaves are palatable and nutritious with crude protein levels ranging from 15-18%. Livestock, including yearling ewes and steers, can gain weight on cheatgrass-dominated rangeland in the spring. Once Cheatgrass plant matures, weight gains drop to zero and plants become unpalatable because of the dry foliage and sharply-awned seeds. Livestock feeding on dry cheatgrass can get lumpy-jaw infections and severe eye injuries.

Cheatgrass florets are susceptible to Ergot, a fungus that is toxic to livestock.

COMPETITION [Adapted from Mosley et al. in Sheley and Petroff 1999]
Cheatgrass can out-compete other plants that are presumed to be competitive. Plants include: Halogeton (Halogeton glomeratus), Tall Tumble-mustard (Sisymbrium altissimum), and Russian Thistle (Salsola tragus). Cheatgrass outcompetes seedlings of many perennial plants because its shallow roots quickly capture available soil moisture. Competition from Cheatgrass can lead to failed seeding applications.

Cheatgrass reproduces by seeds. Cheatgrass populations are genetically similar (Pyke and Novak 1994) but exhibit plasticity that allows it to survive under a variety of site conditions.

LIFE CYCLE [Adapted from Mosley et al. in Sheley and Petroff 1999]
Cheatgrass is an annual, completing its life cycle within one growing season. Typically, it grows, flowers, develops seeds, and becomes fully dry and dies within 2-3 months.

Specifically, Cheatgrass is usually a winter annual. Seeds typically germinate in the early fall when moisture becomes sufficient. They over-winter as small seedlings. However, if the climate is warm and rainy plants continue to grow. Sometimes when the above-growth is minimal the below-growth is more substantial. Cheatgrass roots can grow at cooler temperatures then many other plants can. In the spring plants resume growth when ambient temperatures warm. A single plant can consist of 1-20 tillers and its fibrous root system occurs within the upper 12 inches of the soil profile.

Plants are wind-pollinated. As soon as the fruits start to turn purple, but are largely still green, the seed is viable. Each Cheatgrass plant can produce a lot of seed. During unfavorable conditions, Cheatgrass may remain short, but will produce enough seed to perpetuate itself. Individual plants that grow in high densities can each produce 25 seeds. Individual plants that grow in lower densities with enough moisture and sunlight and that exhibit abundant tillers can produce 5,000 seeds.

Seeds on soil surface can germinate in mesic environments but need to be covered with soil or plant litter in drier climates. Upon sufficient moisture, up to 95% of Cheatgrass seeds will germinate and grow quickly.

Cheatgrass seeds can germinate in the spring, but plants are often fewer, less vigorous, and produce fewer seeds. Where spring is long and wet and there is abundant nitrification, many Cheatgrass seeds will lose their dormancy and germinate.

Wherever Cheatgrass establishes it will be persistent, and eradication is not a reasonable goal in most situations. The strategy chosen to suppress Cheatgrass will determine its level of abundance and role in the community. Sites need to be evaluated to determine how much of the community still has perennial shrubs, forbs, and grasses. In sites devoid of perennial plants, the Cheatgrass community is likely stable and self-perpetuating and control techniques do not need to consider impacts to perennial plants. In sites with seral plant communities that have Cheatgrass, but also have perennial shrubs, forbs, and/or grasses, control techniques that do not harm the perennial vegetation should be implemented.

An integrated vegetative management approach provides the best long-term control, and requires that land-use objectives and a desired plant community be identified (Shelly et al.in Sheley and Petroff 1999). Once identified an integrated weed management strategy to promote a weed-resistant plant community and serve other land-use objectives such as livestock forage, wildlife habitat, or recreation, can be developed.

PREVENTION [Adapted from Sheley and Petroff 1999]
Preventing the establishment of Cheatgrass can be accomplished by many practices:
* Learn how to accurately identify Cheatgrass in order to detect occurrences and know where to implement control methods.
* Implement measures to reduce soil disturbance and improve conditions for perennial plant reproduction.
* Prevent vehicles from driving through and animals from grazing within infested areas.
* Thoroughly wash the undercarriage of vehicles and wheels in a designated area before moving to uninfested areas.
* Frequently monitor for new plants, and when found implement effective control methods.
* Maintain proper grazing management that creates resilience to noxious weed invasion.

PHYSICAL and CULTURAL CONTROLS [Adapted from Mosley in Sheley and Petroff 1999]
Hand-pulling is effective and easy in small areas, gardens, alleys, and other places, particularly when soils are moist. The shallow, fibrous roots system makes it easier for the entire plant to be pulled and bagged. If plants are in the fruit/seed stage then plants should be allowed to desiccate within sealed bags before depositing in the landfill. Hand-pulling should be done at intervals until the seed source is depleted.

Disking creates favorable soil conditions, stimulates seed germination, and is usually not effective. To be effective, tillage must be 10-15 cm deep in order to bury seeds and prevent their germination and be repeated during the season. Increasing the soil bulk density of the soil will inhibit Cheatgrass, but should not be done if it will impact desirable plants.

Revegetating land with competitive, locally adapted, and competitive grasses, forbs, and shrubs will develop a plant community that is more resilient to Cheatgrass. However, establishing the community can be difficult because cheatgrass plants quickly absorb available soil moisture and nutrients. It is necessary to use revegetation in combination with disking, herbicides, or prescribed fire on rangeland to be more effective in reducing Cheatgrass. Details at combining techniques can be found in Mosley in Sheley and Petroff 1999 and with your local County Weed or Farm agents.
NOTE: Cultivars of native grasses do not break down and degrade like true native plants, and will contribute to fuel loads and harming biological soil crusts.

Prescribed Burning is not an effective control method. Burning will decrease above ground biomass, but stimulates seed germination, and decreases competition from desirable plants. Cheatgrass plants that establish after a fire produce more seed per plant.

Mowing is not an effective control method because it distributes seeds, decreases competition from adjacent plants, and maintains conditions that are favorable to Cheatgrass.

CHEMICAL CONTROLS [Adapted from Mosley in Sheley and Petroff 1999]
Herbicides can be effective, when desired perennial plants are still abundant in the community. A single year of herbicide application will temporarily reduce the population, but increase seed production. Chemical control must be repeated for 2 to 5 consecutive years. Combining revegetation with herbicide control can be more effective if done properly. Details at combining techniques can be found in Mosley in Sheley and Petroff 1999.

The herbicide type and concentration, application time and method, environmental constraints, land use practices, local regulations, and other factors will determine its effectiveness and impact to non-target species. Strict adherence to application requirements defined on the herbicide label will reduce risks to human and environmental health. Consult your County Extension Agent and/or Weed District for information on herbicidal control. Chemical information is also available at Greenbook.

Paraquat (0.5 pounds active ingredient (ai) per acre) applied in the spring to the vegetative stage or early dough stage of seed development will provide control if repeated for 2 consecutive years. A surfactant will increase the effectiveness of paraquat.

Glyphosate (0.6 pounds ai per acre) applied in the spring will kill desirable perennial grasses. For Cheatgrass glyphosate (0.5 pounds ai per acre) applied in the spring to the vegetative stage or early dough stage of seed development will provide control if repeated for 3 consecutive years. For Cheatgrass glyphosate (0.4 pounds ai per acre) applied in the spring to the early dough stage of seed development will provide control if repeated for 3 consecutive years.

BIOLOGICAL CONTROLS [Adapted from Mosley in Sheley and Petroff 1999]
No biological control agents are available. Cheatgrass seedheads are susceptible to Ergot, a fungus which will kill seeds.

GRAZING CONTROLS [Adapted from Mosley in Sheley and Petroff 1999]
Livestock grazing can be purposely designed to control Cheatgrass (Megee 1938; Daubenmire 1940; Valentine and Stevens 1994; and Mosely 1996). As a tool it works best when targeted to local areas for the purpose of protecting existing perennial plants from fire or aiding seeding restoration in severely depleted sites.

To control Cheatgrass targeted grazing must be done at least twice per season for at least two consecutive years. The grazing intensity should be light enough to maintain a minimum 8 cm (3 inches) stubble height on desirable grasses. The first grazing should be done in the spring when plants are tall enough to become accessible and palatable, but before plants turn purplish (before they reach the soft dough stage of seed development). This will prevent most seed development. The second grazing should occur in late spring during the boot stage, then allowed to re-grow for 3-4 weeks before re-grazing.

Grazing intensities in winter can be moderate to heavy without damaging perennial plants, as long as soils are dry and firm.

Prescribed grazing can also reduce litter build-up, disrupting the fire cycle, reducing the fuel loads, and enhance the competitiveness from perennial plants. Grazed firelines should be at least 75 meters (250 feet) wide.

Useful Links:
Montana Invasive Species website
Montana Biological Weed Control Coordination Project
Montana Department of Agriculture - Noxious Weeds
Montana Weed Control Association
Montana Weed Control Association Contacts Webpage.
Montana Fish, Wildlife, and Parks - Noxious Weeds
Montana State University Integrated Pest Management Extension
Weed Publications at Montana State University Extension - MontGuides

Cheatgrass can significantly alter the composition of native rangeland vegetation because it is a strong colonizer and competitor and facilitates wildfires (Mosley et al. in Sheley and Petroff 1999). In drier prairies and sagebrush steppe habitats it has colonized ground that naturally had low frequencies of forbs and grasses and higher coverage of intact biological soils crusts. Where the soil surface becomes disturbed, cheatgrass plants easily colonize and develop dense populations. Their foliage dries out sooner than perennial grasses and their litter builds up creating more frequent fire intervals and more uniform fires (Mosley et al. in Sheley and Petroff 1999) See ECOLOGY / VULNERABLE HABITATS section.

Cheatgrass adds organic matter to the soil surface, which acts as a mulch. This mulch favors the establishment of Cheatgrass seedlings while inhibiting the perennial bunchgrasses. Persistent and heavy mulch covers ground layer organisms, particularly biological soil crusts, eventually killing them (Weber, Budel, and Belnap (editors) 2016).

Cheatgrass-infested rangelands have less plant production than native rangelands (Mosley et al. in Sheley and Petroff 1999). Cheatgrass plants are only nutritious when green and young, which lasts for about 6-8 weeks. Mostly perennial grasses remain green and nutritious for longer periods. The short ‘green’ period of Cheatgrass reduces the length of forage production that a site could support for livestock and native ungulates if occupied by perennial grasses.