Medusahead

Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.

Taeniatherum caput-medusae

Colorado noxious weed · List A — Eradicate. CO-rules-2025

Uncommon in Colorado. All populations are designated for eradication statewide. This is a management category, separate from danger ratings. Category source · What the lists mean.

Barbed awns; persistent fire-promoting thatch. Exposure help.

Identification caveat: Similar-looking native grasses exist. Awn and spike structure must be examined before identification or removal.

Still researching this plant

This is a sourced working profile. Evidence is incomplete for Other animals. Identification and source-photo limits are explained below. Independent botanical and veterinary review is pending. Uncertainty is not a finding that the plant is safe.

Three views of this plant

Source-identified reference photographs; these are not a complete identification key. A source location outside Colorado does not establish local occurrence.

Taeniatherum caput-medusae: Dense grass growth with numerous pale, spreading, long-awned heads. — **maturing heads** — Dense grass growth with numerous pale, spreading, long-awned heads.
Matt Lavin from Bozeman, Montana, USA · CC BY-SA 2.0
Photo source and identification
Original record · Original image
Source scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination.
Wikimedia server-resized derivative; no local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Taeniatherum caput-medusae: A broad straw-coloured stand beside a fence and building. — **infestation** — A broad straw-coloured stand beside a fence and building.
Matt Lavin from Bozeman, Montana, USA · CC BY-SA 2.0
Photo source and identification
Original record · Original image
Source scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination.
Wikimedia server-resized derivative; no local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Taeniatherum caput-medusae: Close view of green spikes with numerous long, slender awns. — **green heads** — Close view of green spikes with numerous long, slender awns.
Matt Lavin from Bozeman, Montana, USA · CC BY-SA 2.0
Photo source and identification
Original record · Original image
Source scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination.
Wikimedia server-resized derivative; no local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Recognize

A winter annual grass with dense seed spikes and long, twisting, barbed awns. WA-medusahead

Plants & habitat

Competes strongly with native vegetation. Slowly decomposing, silica-rich thatch accumulates and can increase fire frequency. WA-medusahead

People

Barbed awns catch on clothing and can scratch; avoid bare-handed handling of mature seedheads. WA-medusahead

Dogs & cats

Awns pose a plausible physical injury concern, but this source is not a species-specific pet case series. Keep pets out of mature seedheads. WA-medusahead

Other animals

Poor forage quality and loss of desirable pasture are documented concerns. An unrestricted feeding-safety threshold is not established. WA-medusahead

Before taking action

Confirm identification and the requirements of your county weed program. For chemical treatment, follow the current product label, including restrictions around animals and water. S27

This is a statewide eradication priority. Contact your county weed program promptly for identification and an approved management and disposal plan. CO-rules-2025

References

CO-rules-2025 — Colorado Noxious Weed Act rules, 8 CCR 1206-2, Colorado Secretary of State / Department of Agriculture. Accessed 2026-09-07T01:07:48+00:00. Locator: Parts 3.1, 4.1, 5.1; management provisions; effective May 15, 2025.
WA-medusahead — Medusahead, Washington State Noxious Weed Control Board. Accessed 2026-09-07T01:09:00+00:00. Locator: Identification, ecological impacts, management; Washington legal class not applied to Colorado.
S27 — 2103 – Colorado Noxious Weeds, PlantTalk Colorado · CSU Extension. Accessed 2026-09-07T00:23:57+00:00. Locator: List A, B and C management categories.

Content revised 2026-09-07 03:50:00Z · Source checks dated separately in the references.