Quackgrass

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

Elymus repens

Colorado noxious weed · List C — Manage widespread weeds. CO-rules-2025

Widespread and well established. Control is recommended by the state; local governments may require management. This is a management category, separate from danger ratings. Category source · What the lists mean.

Rhizome fragments regrow in lawns and gardens. Exposure help.

Still researching this plant

This is a sourced working profile. Evidence is incomplete for People, Dogs & cats, Other animals. 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.

Elymus repens: Dense upright grass clump with long green blades and slender flower spikes. — **habit** — Dense upright grass clump with long green blades and slender flower spikes.
Rasbak · CC BY-SA 3.0
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Source names Elytrigia repens and Elymus repens are treated as synonyms. Similar grasses require spikelet orientation and leaf-collar characters for an unknown specimen.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Elymus repens: Flattened spikelets arranged along a narrow spike, with pale anthers protruding. — **flower** — Flattened spikelets arranged along a narrow spike, with pale anthers protruding.
James K. Lindsey · CC BY-SA 2.5
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Source names Elytrigia repens and Elymus repens are treated as synonyms. Similar grasses require spikelet orientation and leaf-collar characters for an unknown specimen.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Elymus repens: Close view of a leaf base and collar clasping a green culm, with a scale. — **leaf-node** — Close view of a leaf base and collar clasping a green culm, with a scale.
Stefan.lefnaer · CC BY-SA 4.0
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Source names Elytrigia repens and Elymus repens are treated as synonyms. Similar grasses require spikelet orientation and leaf-collar characters for an unknown specimen.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Recognize

A perennial grass with clasping auricles at the leaf collar and pale underground rhizomes with sharp tips. M-quackgrass

Plants & habitat

Rhizomes compete with desired vegetation and regrow from pieces. Repeated disturbance without removing or exhausting them can spread the patch. M-quackgrass

People

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for people. Missing evidence does not establish safety.

Dogs & cats

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for dogs or cats. Missing evidence does not establish safety.

Other animals

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for livestock. Missing evidence does not establish safety.

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

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.
M-quackgrass — Quackgrass, University of Minnesota Extension. Accessed 2026-09-07T01:16:17+00:00. Locator: Species identity, description, ecological and exposure evidence; verify group scope.
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.