Source: California Invasive Plant Council

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Invasive Plants of California's Wildland

Taeniatherum caput-medusae
Scientific name   Taeniatherum caput-medusae
Additional name information: (L.) Nevski
Common name medusahead
Synonymous scientific names Elymus caput-medusae
Closely related California natives Elymus arizonacus, E. canadensis
Closely related California non-natives: 2
Listed CalEPPC List A-1,CDFA nl
By: Oren Pollack,Tamara Kan

Distinctive features:

Medusahead (Taeniatherum caput-medusae) is a slender annual grass. The one- to three-inch awns are straight and compressed when green, but, upon drying, the awns twist and spread erratically in a manner reminiscent of the snake-covered head of the mythic Medusa. Medusahead can often be recognized by its color, which stands out against surrounding grasses. It matures from two to four weeks later than most other annual grasses, displaying distinctive patches of green in an otherwise brown grassland. After seed production, the dead medusahead plants bleach to light gray or tan. Medusahead is sometimes confused with foxtail (Alopecurus sp.) or with squirreltail (Elymus elymoides); however, medusahead’s spike head does not break apart as seeds mature.


Poaceae. Stems: 8-24 in (2-6 dm) long, slender, decumbent to ascending. Leaves: sheath glabrous, appendages <0.1 in (3 mm); ligule <0.2 in (0.5 mm), truncate; blade 1-3 mm wide, +/- inrolled, glabrous to puberulent, long-ciliate near collar.
Inflorescence: 0.6-2 in (1.5-5 cm) excluding awns. Awns 1-3 in (2.5-7.5 cm), straight and compressed when green, twisting when dry. Spikelet: glumes 0.6-1.6 in (1.5-4 cm), fused at base, awn-like, stiff, generally glabrous; lemma narrowly lanceolate; awn 0.6-2 in (1.5-7.5 cm), flat, straight to curving outward (Hickman 1993).


As recently as 1950 medusahead was reported from only six counties in northwestern California. It has since spread rapidly throughout California, and currently is known to occur in over twenty counties (Pollak pers. observation). It has been reported from almost every county in northern California and in many areas of central California, extending as far south as Riverside County. It also infests rangeland, grassland, and sagebrush communities in Oregon, Washington, Idaho, Nevada, and Utah.

Medusahead invades grasslands, oak savannah, oak woodland, and chaparral communities. It grows in a wide range of climatic conditions. Clay or clay-loam soils with at least ten inches of rainfall annually are most susceptible to invasion (Dahl and Tisdale 1975). However, medusahead has been found on coarse-textured soils as well (Young 1992).



Medusahead is native to Spain, Portugal, southern France, Morocco, and Algeria. It was introduced to the United States in the late 1800s. The grass reproduces by seed, which is dispersed locally by wind and water. The long-awned seeds cling to the coats of grazing animals, such as sheep or cattle, and in this way are transported to more distant sites. Seeds can also disperse by attaching to machinery, vehicles, and clothing.



Medusahead outcompetes native grasses and forbs, and, once established, can reach densities of 1,000 to 2,000 plants per square meter. After seed set, the silica-rich plants persist as a dense litter layer that prevents germination and survival of native species, ties up nutrients, and contributes to fire danger in summer. Because of its high silica content, medusahead is unpalatable to livestock and native wildlife except early in the growing season. The sharp awns can injure the eyes and mouths of livestock.



Medusahead is predominantly self-pollinating and reproduces by seed. Flowering usually occurs in May. An average of eight to fifteen seeds are produced per spike in late

(click on photos to view larger image)


spring or early summer. Seeds usually disperse by mid-summer. Seed dormancy varies from a few weeks to over six months, depending on location. Germination normally occurs with the first rains in fall, and the germination rate is high. The seeds are well adapted to germinating and growing in the dense litter layer. Under these conditions, seeds can germinate even if they are not touching the soil. If they dry out, the primary root dies; but if they are moistened again, a new adventitious root develops (Young et al. 1971).

In California medusahead seeds usually germinate in October or November. The shoot system remains small, while the root system develops throughout the cold winter months. Early germination and rapid root growth consumes available water and nutrients, outcompeting slower-growing native species. Medusahead continues to grow, extract soil moisture, and produce seeds after most other annual grasses have turned brown.



Physical control:

Mechanical methods: Mowing alone, or in combination with grazing, was found to be effective in reducing infestations. Plowing or discing are also effective means for controlling medusahead (Hilken and Miller 1980).

Prescribed burning: Several studies have shown that burning stands of medusahead prior to seed dispersal is an effective control measure (Furbush 1953, Hilken and Miller 1980, McKell et al. 1962, Murphy and Lusk 1961, Pollak and Kan 1996). Burns should be scheduled for late spring, after seed set but before seed heads have shattered (known as the “soft dough” stage of seed development). Seeds still on the plants are destroyed by the burn, while dispersed seeds lying on or buried below the soil surface are protected from the intense heat of the burn. With few seed reserves in the soil, medusahead abundance can be dramatically reduced if the seed input for even one year is eliminated.

This method takes advantage of the fact that medusahead matures later than most of the surrounding vegetation, so most other species have already dispersed their seeds and are dry enough to carry a burn. At the Jepson Prairie Preserve in Solano County effective control burns were conducted in late May and early June. Proper timing may vary depending on local conditions and weather. Some studies have found medusahead to increase after burning, but most of these studies conducted burns in August, presumably after seed dispersal.


Biological control:

Insect and fungi: No insect or fungal control agents are known. However, some preliminary research has been done on the effect of dry soil conditions on infestations of crown rot (Fusarium culmoron), a soil-borne pathogen, on medusahead (Grey et al. 1995).

Grazing: Heavy grazing by sheep in early spring (when medusahead is still palatable) can assist in controlling medusahead, but animals should be removed before seed heads form to limit seed dispersal. Early spring grazing is especially effective in areas where dried medusahead litter has been previously burned or grazed. Fertilizing with nitrogen improves the palatability of medusahead (Lusk et al. 1961). Properly timed grazing may reduce, but not eliminate, medusahead infestations.


Chemical control:

Small-scale infestations can be controlled by chemical herbicides. Atrazine applied in fall at 2 lbs/acre, was effective in controlling medusahead (Hilken and Miller, 1980). Check with a certified herbicide applicator or the herbicide label for current registration information.