Medusahead Rye (Taeniatherum caput-medusa)
Medusahead rye is a winter annual grass that flowers from May through June. It germinates in late fall or early spring and completes its life cycle by early summer.
Plants produce slender stems ranging from 6 to 24 inches tall, often with several stems arising from the base. While the plant produces tillers (new shoots), it generally does not produce many leaves. Leaves are narrow (about ⅛ inch wide), rolled, and may have short, soft hairs. Auricles are usually present but very small (about 0.5 mm long).
The inflorescence is a dense spike with very long awns, making the seedhead nearly as wide as it is long. Each spikelet contains stiff awns 1 to 3 inches long, tipped with minute barbs. At maturity, awns twist and may reach up to 4 inches long, giving the plant its characteristic “Medusa-like” appearance. Seedheads are bristly and often persist through winter.
Seeds are narrow, ⅛ to ¼ inch long, and remain viable for approximately two years. Medusahead rye has a shallow, fibrous root system.
Like other invasive annual grasses, medusahead contains high levels of silica, which slows decomposition and leads to dense accumulations of thatch or duff. This buildup can alter fire regimes and suppress desirable vegetation.
Quick ID Guide
Life Cycle:
• Winter annual
• Germinates in fall or early spring
Height:
• 6–24 inches
Stems:
• Slender
• Several from base
• Produces tillers
Leaves:
• Narrow (⅛ inch)
• Rolled
• Slightly hairy
• Small auricles present
Flowers (Late Spring–Mid Summer):
• Spike inflorescence
• Long, stiff awns (1–4 inches)
• Minute barbs
• Twist at maturity
Seeds:
• Narrow• ⅛–¼ inch long
• Viable ~2 years
Roots:
• Shallow, fibrous
Management Options
Prevention and cultural control strategies should be prioritized. Use certified weed-free forage and gravel, clean construction equipment before moving between sites, and clean recreational gear, clothing, and pets after recreating to prevent the spread.
There are currently no approved biological control agents for medusahead rye.
Hand pulling small infestations before seed maturation is highly effective. Shallow cultivation, including hoeing or tilling immediately after germination and before flower production, can also provide good control. Mowing is only recommended before inflorescences develop. Grazing is generally not effective and should be avoided once seedheads form, as stiff awns can injure livestock.
Large infestations typically require herbicide treatment. Most herbicides (except glyphosate) are applied preemergence to prevent germination. Glyphosate is effective only before seed production. Preemergent applications are commonly made in late summer (often August), depending on moisture requirements. Always read and follow herbicide label directions before application. Contact Sublette County Weed & Pest for assistance with product selection, rates, and timing.
