Eastern Forest Threat Center - Medusahead

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Steve Dewey, Utah State University, Bugwood.org

Taeniatherum caput-medusae

Medusahead is an annual grass native to Eurasia. A low-value forage species for livestock and wildlife, it has been estimated that the carrying capacity of rangeland for domestic livestock has been reduced by 75% after medusahead invasion.

Keywords: Poaceae, winter annual, grass, spike, twisted awns, wiry stems, high silica content, fibrous root system, rapid germination, dense stands

Distribution Map Distribution Source Image

Threat Description

Medusahead is a winter annual grass. It can be singled out by its spike and seed head that does not break apart as seeds mature. Individual awned florets fall away, leaving twisted awns that will hold all winter. The yellowish-green sheen of dense stands is highly visible after other annual grasses turn brown. Slender wiry stems contain a few short narrow leaves. Medusahead tissues have a high silica content and low palatability except during the early growth stages. The high silica content also makes the litter of dead stems slow to decompose. Medusahead quickly develops a fibrous root system allowing it to extract available soil moisture deep in the soil profile. It reproduces by seeds that disperse locally with wind, water, and by clinging to the feet and fur of animals. Germination is typically rapid and occurs under a broad temperature range. Most seeds germinate in fall after the first rain, but some remain dormant or germinate in winter or spring. Medusahead inhabits disturbed sites, grassland, openings in chaparral, oak woodlands, and rangelands. It tends to grow best on clay soils where deep soil moisture is available late in the growing season.