Invasive Medushead in Western States

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Medusahead ( Taeniatherum caput-meduse) is native to the Mediterranean region and is an important member of a group of grasses that includes wheat, barley, and ceral rye. Medusahead was first recorded in the United States near Roseburg, Oregon, in 1887 (Howell 1903). Herbarium records indicate that the plant spread concentrically – north into Washington, south into California, and east into the Great Basin, Idaho, and other western states. It is not known how medusahead was introduced to the United States, however, it has been suggested that medusahead arrived as a contaminant in cereal grain seed, while others (George 1992; Hilken and Miller 1980) suggest it may have arrived clinging to the fur of imported livestock. Once introduced to the western US, medusahead spread rapidly in low-elevation annual grasslands, woodlands, and chaparral communities. These west coast plant communities have a similar climate to the Mediterranean region: hot and dry summers, and cool, moist falls. In both lowland rangelands and in high-elevation semiarid systems, medusahead is considered to be an ecosystem transformer species (Richardson et al. 2000; Wells et al. 1986). This places it among the worst weeds: not only does medusahead compete for resources with more desirable species, but it changes ecosystem function to favor its own survival at the expense of the entire ecosystem. Displacement of natural vegetation by medusahead has substantial impacts on the structure, organization and functioning of western ecosystems.

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It's no secret that extensive stands of pinyon juniper and sagebrusg steppe exist across the American West. In semiarid big sagebrush steppe and woodlands, medusahead acts as a fire promoter. Like other annual grasses, medusahead fills in between the native vegetation, creating a continuous fuel corridor that accelerates the fire cycle,  posing a risk of fire during any season. Because of these the mean fire return interval on disturbed sites is greatly reduced.

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It can be difficult to selectively remove an invasive grass such as medusahead from a grassland, steppe, or woodland community. For this reason, medusa is often burned during late spring at high temperatures when the seeds are still present on the plant to promote mortality.Following a burn, other control techniques such as grazing, revegetation, and preemergence herbicides are often used as appropriate land managment tools for medusahead in areas with high annual grass biomass production.






George MR (1992) Ecology and Management of Medusahead. Davis, CA: University of California Range Science Report 31:1-3

Hilken TO, Miller RF (1980) Medusahead (Taeniatherum asperum Nevski): A review and annotated bibliography. Oregon State University Agricultural Experiment Station Bulletin 644, Corvallis, Oregon, USA

Howell TJ (1903) A Flora of Northwest America. Self-published. Portland, Oregon.

Richardson DM, Pysek P, Rejmanek M, Barbour MG, Panetta FD, West CJ (2000) Naturalization and invasion of alien plants: concepts and definitions. Divers Distrib 6:93-107