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Home>Plant Species>Weed Species>Medusahead rye

Drawing of medusahead rye Medusahead rye
Taeniatherum caput-medusae (Taeniatherum asperum, Elymus caput-medusae)

question markDid you know?

Medusahead is rich in silica, causing its litter to decompose very slowly!

How did medusahead get here?
Medusahead made its début in the United States in the 1880s near Roseburg, Oregon. It is speculated that it first arrived from Europe with imported animals, either in bedding or attached to their fur. Medusahead has yet to complete its destructive journey.

Medusahead rye seed headWhat are its characteristics?
Like cheatgrass, this is a winter annual grass. Height ranges from 6 to 24 inches tall and it has a seed head with long awns that are stiff and slightly barbed. The name medusahead is due to these wiry awns. The mature plant has a slender stem with narrow leaves. Roots can grow at cold temperatures and seeds mature quickly. Medusahead plants are rich in silica, and its litter breaks down more slowly than most other grass species.

The growth habit, life cycle, and adaptations of medusahead and cheatgrass are similar, and they often grow together. In some areas, medusahead out-competes cheatgrass to become the dominant vegetation. This has occurred on disturbed sites with clay soils that have high moisture-holding capacities.

Image of cows along a trail with medusahead plants starting

Why is medusahead a problem in the Great Basin? Medusahead thatch with a pen for scale
Medusahead has several weapons in its invasive arsenal. These include rapid fall germination and root growth throughout the winter, prolific seed production, and accumulation of litter that decomposes slowly. The dense litter cover is important in its competitive relationship with other annuals because most competitors fail to grow under the accumulated thatch. Essentially useless as forage, medusahead has been estimated to reduce the carrying capacity of infested rangeland by 75 percent for domestic livestock.

How can we fight this weed?
Fire, herbicides, disking, and intensive early grazing can all reduce medusahead infestations, but revegetation with desirable species is vital to prevent medusahead from regaining dominance after control treatments. A slow hot fire after medusahead seeds ripen, but before they drop, can reduce medusahead up to 90 percent the following year.

-Drawing: USDA-NRCS PLANTS Database / Hitchcock, A.S. (rev. A. Chase). 1950. Manual of the grasses of the United States. USDA Misc. Publ. No. 200. Washington, DC.
-Seed head: Carol W. Witham, CalPhotos database.
-Thatch: USDA Forest Service.

Text references:
-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). Available: (, 26 September 2006).
-USDA, NRCS. 2006. The PLANTS Database (, 26 September 2006). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
-Whitson, T. D., 2000. Weeds of the West., 9th ed. Western Society of Weed Science, Newark, CA.