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(Taeniatherum caput-medusae)

Photo of medusahead
Photo credit: Steve Dewey

Invasive annual grass that is severely destructive of rangelands across western and central United States.

 Overview map of prohibited classification in WI
Prohibited (red) counties

Other names for this plant include:

  • Common names: medusahead rye
  • Scientific names: Taeniatherum caput-medusae ssp. asperum, Taeniatherum asperum, Taeniatherum crinitum var. caput-medusae, Elymus caput-medusae

Classification in Wisconsin: Prohibited

Ecological Threat
  • It invades grasslands, forests, prairies, and disturbed areas such as grazed lands and fields.
  • In the western United States, it decreases shrub/perennial grass ecosystems and native vegetation, shifting it to an annual grass ecosystem.
  • Reduces the value of grazing lands by more than 80%.
  • Produces extremely large amounts of viable seed, with up to 6,000 seeds per square foot.
  • Documented to reach densities of 1,000 to 2,000 plants per square meter.
  • Allelopathy has been demonstrated on wild oats.
  • Disrupts nutrient cycling and availability, alters soil chemistry and changes fire frequency.

Leaves & stems: This slender grass grows 6-20 inches tall. One or more stems arise from the base of the plant. Leaf-blades somewhat rolled.

Flowers, fruits & seeds: Each stem produces a single seed head. Nodding spikes are dense bristly seed heads with long awns reaching 1-4 inches in length. Seed heads have 2 sets of bristles; shorter ones extend at an angle, longer ones are erect. Each spikelet contains one seed. Each seed head produces 20 or more seeds.

Roots: Shallow root systems.

Similar species: Medusahead resembles foxtail barley (Hordeum jubatum; non-native) because of their similar long, numerous awns. Medusahead can be distinguished because inflorescence does not break apart upon maturity.


Currently, there have been no reports of medusahead in Wisconsin. Have you seen it? Send us a report.


Treatment varies depending on surrounding plant communities and site ecological characteristics. See the resources tab for more information.

  • Tillage is extremely effective. Till prior to flowering to prevent seed production. Multiple tillings may be needed because plants can flower multiple times.
  • Mowing prior to seed-set may also reduce medusahead coverage the following year.
  • Glyphosate can be effective when applied in early spring to young plants.
  • Imazapic applications following prescribed burns are reported as more effective than herbicide alone.
Prescribed Fire:
  • Burning just prior to seed-drop is the most effective control technique. Depending on the timing, burning may produce inconsistent results.
Sources for content:
  • Archer, Amy J. 2001. Taeniatherum caput-medusae. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). [Accessed 2007, Sept. 26].
  • Johnson, Dustin D. and Davies, Kirk W. 2012. Medusahead Management in Sagebrush–Steppe Rangelands: Prevention, Control, and Revegetation. Society for Range Management, Rangelands 34(1):32-38. 2012.
  • Eastern Forest Environmental Threat Assessment Center
  • Center for Invasive Species and Ecosystem Health;
Links for more information: