Submitted to: CABI Crop Protection Compendium
Publication Type: Book / Chapter
Publication Acceptance Date: October 20, 2003
Publication Date: March 1, 2004
Citation: Young, J.A., Clements, C.D. 2004. Cheatgrass. CABI Crop Protection Compendium Datasheet: Invasive Plants, Text Section. p. 1-19 Interpretive Summary: Cheatgrass (Bromus tectorum L.) is a serious invasive weed of North America. Native to Central Asia, it was first discovered in the United States in 1861 in Pennsylvania. Cheatgrass is now found in all states including Alaska. Cheatgrass was widely distributed through grain crops infested with this weed through uncleaned threshing equipment that moved from farm to farm and through the railway systems. Once established cheatgrass truncates succession by out competing the native perennial species. Cheatgrass increases the chance of ignition, rate, spread and season of wildfires. This increased frequency of wildfires leads to its dominance on rangelands. In dense stands 8,500 to 11,000 plants per m² can be witnessed. In these dense stands cheatgrass may produce a single stem and a single diminutive panicle. In very sparse stands (10 per m²) such as the year following a wildfire, cheatgrass may have a multitude of robust panicles of florets. Cheatgrass has the ability to germinate in the fall as a winter annual in some environments, while in other environments germinate in the spring. Cheatgrass can germinate at very cold temperatures, a constant 0°C, at very warm temperatures at 40°C constant temperature as well as at wide variable temperatures that range from 0° to 40°C. In more recent times cheatgrass has invaded the salt desert shrub habitats of the Great Basin as well as the more xeric high elevational mountain brush communities. The aggressive nature of this invasive weed species continues to cross formerly believed barriers causing much concern among the scientific and common public.
Technical Abstract: Cheatgrass (Bromus tectorum L.), native to Central Asia, is widely known for its invasive nature throughout Western North America. First identified in the United States in 1861 in the state of Pennsylvania followed by Washington 1893, Utah 1894, Colorado 1895, Wyoming 1900, and Nevada 1901. Cheatgrass can now be found in all of the lower 48 states as well as Alaska. The spread of cheatgrass can most likely be attributed to contaminated grain through uncleaned threshing equipment that made its way from farm to farm and dispersal through the railway system. Once known to be a weed of roadsides, fence lines and ditch ways, now has spread throughout millions of hectares of crop and rangelands. Generally, the habitat of cheatgrass is referred to as disturbed plant communities, yet Daubenmire (1940) conclusively demonstrated that cheatgrass could invade native high ecological condition bluebunch wheatgrass (Pseudoroegneria spicatum) communities that had always been protected by grazing by large herbivores. Dense stands of cheatgrass can reach the neighborhood of 8,500 to 11,000 plants per m², as little as 12 plants per m² can severely limit the growth of perennial grass seedlings. Cheatgrass has more recently moved into the salt desert shrub environments of the Great Basin as cheatgrass is largely a self pollinated species that is conditioned to environmentally to occasional out-crossing. This allows it to establish to a site where it is genotypically a good fit to the environmental potential of the site. It then populates the site with off spring with stable duplicates of the desired genotype through self fertilization. Occasionally, environmental conditions would be adequate to allow these self pollinated species to cross breed and produce hybrid off spring. The noted plant ecologist, D. W. Billings, termed cheatgrass a biotic cause of ecosystem impovershment. The aggressive nature of cheatgrass continues to cross formerly believed barriers causing much concern among the scientific and public community.