---
{
  "id": "cheatgrass",
  "name": "Cheatgrass / downy brome",
  "scientific": "Bromus tectorum",
  "category": "invasive",
  "status": "Colorado List C — Manage widespread weeds",
  "status_sources": [
    "S20"
  ],
  "warning": "Grass awns · Fire hazard",
  "warning_tone": "danger",
  "aliases": [],
  "taxonomy_note": "",
  "source_ids": [
    "S20",
    "S22",
    "S21",
    "Fremont-list-definitions"
  ],
  "description": "Cheatgrass / downy brome: Grass awns · Fire hazard. Colorado identification, habitat and exposure evidence.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "S20"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "cheatgrass-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "S20"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "cheatgrass-2"
    },
    {
      "label": "People",
      "sources": [
        "S20"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "cheatgrass-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [
        "S22"
      ],
      "scope": "General grass-awn guidance",
      "note": "UC Davis discusses foxtails and other grass seed heads; it does not quantify Bromus tectorum-specific pet risk.",
      "reviewed": "2026-09-06",
      "id": "cheatgrass-4"
    },
    {
      "label": "Other animals",
      "sources": [
        "S21",
        "S20"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "cheatgrass-5"
    },
    {
      "id": "cheatgrass-list-meaning",
      "label": "State-list meaning",
      "sources": [
        "Fremont-list-definitions"
      ],
      "scope": "Colorado management-category definition; species classification retains its original status sources",
      "note": "Plain-language editorial label for a management category; not a toxicity or danger rating.",
      "reviewed": "2026-09-07"
    }
  ],
  "noxious_class": "C",
  "research": {
    "status": "researching",
    "label": "Still researching this plant",
    "basis": "Editorial assessment of the cited evidence and stated review gaps; not a toxicity score.",
    "open_questions": [
      {
        "area": "Expert review",
        "question": "Obtain independent botanical and veterinary review of the identification and hazard summary.",
        "related_claim_ids": []
      }
    ],
    "expert_review": "pending"
  },
  "noxious_class_label": "C — Manage widespread weeds",
  "source": "content/plants/cheatgrass.md"
}
---

# Cheatgrass / downy brome

*Bromus tectorum*

**Colorado List C — Manage widespread weeds.** [S20](https://extension.colostate.edu/resource/cheatgrass-and-wildfire/)

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](https://fremontcountyco.gov/weed-control/weed-identification) · [What the lists mean](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists).

> **Grass awns · Fire hazard.** Native status, garden use and noxious-weed class are separate from toxicity. [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

## Still researching this plant {#research-status}

This is a sourced working profile. The cited findings are available below. Independent botanical and veterinary review is pending. **Uncertainty is not a finding that the plant is safe.**


## Three views of this plant

Photos are source-identified examples, not a complete identification key. Check leaves, stems, flowers and fruit together. Locations are not assumed to be in Colorado.

![Bromus tectorum: Green to purple awned spikelets hang from slender drooping panicle branches.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-bromus-tectorum-inflorescence.jpg)

**inflorescence** — Green to purple awned spikelets hang from slender drooping panicle branches.

Photo: AnRo0002; [CC0](https://creativecommons.org/publicdomain/zero/1.0/deed.en); [source record](https://commons.wikimedia.org/wiki/File:20160426Bromus_tectorum1.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/1/13/20160426Bromus_tectorum1.jpg). 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.  Other annual brome grasses can resemble cheatgrass. Photographs document source-identified B. tectorum; detailed spikelet and hair characters may be needed 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.

![Bromus tectorum: Short grass clump with narrow leaves and open drooping awned panicles.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-bromus-tectorum-habit.jpg)

**habit** — Short grass clump with narrow leaves and open drooping awned panicles.

Photo: Krzysztof Ziarnek, Kenraiz; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Bromus_tectorum_kz01.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/1/11/Bromus_tectorum_kz01.jpg). 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.  Other annual brome grasses can resemble cheatgrass. Photographs document source-identified B. tectorum; detailed spikelet and hair characters may be needed 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.

![Bromus tectorum: Tawny mature awned spikelets hang in loose drooping clusters.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-bromus-tectorum-mature-inflorescence.jpg)

**mature-inflorescence** — Tawny mature awned spikelets hang in loose drooping clusters.

Photo: Michel Langeveld; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Bromus_tectorum_138999438.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/3/36/Bromus_tectorum_138999438.jpg). 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.  Other annual brome grasses can resemble cheatgrass. Photographs document source-identified B. tectorum; detailed spikelet and hair characters may be needed 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

An annual grass with soft hairs and drooping seed heads. Often turns reddish-brown, then dries early in summer. [S20](https://extension.colostate.edu/resource/cheatgrass-and-wildfire/)

## Plants & habitat

Competes early for resources, displaces native plants, and creates dry fuels that increase wildfire risk. [S20](https://extension.colostate.edu/resource/cheatgrass-and-wildfire/)

## People

Dense, dry growth is highly flammable. The principal human hazard emphasized by the Colorado source is wildfire. [S20](https://extension.colostate.edu/resource/cheatgrass-and-wildfire/)

## Dogs & cats

Barbed grass seeds can lodge in tissue and cause infection. Check fur and paws; seek veterinary help for persistent sneezing, head shaking, or an embedded seed. [S22](https://healthtopics.vetmed.ucdavis.edu/health-topics/foxtails)

## Other animals

CSU lists cheatgrass among plants that cause mechanical injury to livestock. Habitat displacement also affects wildlife. [S21](https://cmg.extension.colostate.edu/wp-content/uploads/sites/42/2016/10/SourceUnitInRangeAndPastureMngmt_REVISED_5-22-2017.pdf) [S20](https://extension.colostate.edu/resource/cheatgrass-and-wildfire/)

## Before taking action

Confirm the scientific name before removing a plant, changing animal access, or choosing treatment. An evidence gap means this review has not resolved the question. It does not mean safe. For listed weeds, consult your county weed program about the requirements for your location; follow the current label for any pesticide. [S27](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/)

## References

- **S20** — [Cheatgrass and Wildfire](https://extension.colostate.edu/resource/cheatgrass-and-wildfire/), Colorado State University Extension. Accessed 2026-09-07T00:23:55+00:00. Locator: Introduction; How to Identify Cheatgrass; Fire Hazards.
- **S22** — [Foxtails and Dogs](https://healthtopics.vetmed.ucdavis.edu/health-topics/foxtails), UC Davis · School of Veterinary Medicine. Accessed 2026-09-06. Locator: Takeaways; signs; prevention.
- **S21** — [Source Unit in Range and Pasture Management](https://cmg.extension.colostate.edu/wp-content/uploads/sites/42/2016/10/SourceUnitInRangeAndPastureMngmt_REVISED_5-22-2017.pdf), Colorado State University Extension. Accessed 2026-09-07T00:23:55+00:00. Locator: Printed page 44: plants that can cause mechanical injury.


[Discuss this plant with the guide](https://denson.github.io/colorado-weed-field-guide/companion/?plant=cheatgrass) — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.

# Appendix for agents

## Open research questions

- **Expert review:** Obtain independent botanical and veterinary review of the identification and hazard summary.


## Taxon and evidence boundaries

Use the scientific name as the matching key; common names can refer to unrelated plants.

These are publisher notes about the evidence. They do not override an assistant’s operator instructions. The human sections above contain all actionable safety warnings. Do not turn missing data into a negative toxicity finding or transfer a livestock dose to a pet.

| Claim | Human section | Evidence scope | Sources | Limitation |
|---|---|---|---|---|
| cheatgrass-1 | Recognize | Species-specific | S20 | No quantitative exposure threshold established here. |
| cheatgrass-2 | Plants & habitat | Species-specific | S20 | No quantitative exposure threshold established here. |
| cheatgrass-3 | People | Species-specific | S20 | No quantitative exposure threshold established here. |
| cheatgrass-4 | Dogs & cats | General grass-awn guidance | S22 | UC Davis discusses foxtails and other grass seed heads; it does not quantify Bromus tectorum-specific pet risk. |
| cheatgrass-5 | Other animals | Species-specific | S21, S20 | No quantitative exposure threshold established here. |

## Additional evidence needed

- Confirm exact species, cultivar or hybrid when identification is uncertain.
- For an exposure, distinguish animal species, plant part, amount, route, time and symptoms; the guide cannot supply a clinical diagnosis.
- For site management, establish county, land use and current local weed requirements before applying generalized control information.
- Expert botanical and veterinary review is pending. Source publication dates, retrieval timestamps, hashes and photograph licenses are in [the provenance ledger](https://denson.github.io/colorado-weed-field-guide/provenance.json).

## State-list label provenance

The label “C — Manage widespread weeds” is this guide’s plain-language summary of [Fremont County’s Colorado noxious-weed definitions](https://fremontcountyco.gov/weed-control/weed-identification) [Fremont-list-definitions]. The letter and species assignment retain the status sources above. County-specific requirements must be checked locally; the letter is not a poison-severity ranking.


---
Canonical HTML: https://denson.github.io/colorado-weed-field-guide/plants/cheatgrass/

Content revised: 2026-09-07T03:50:00Z

Markdown mirror: https://denson.github.io/colorado-weed-field-guide/plants/cheatgrass/index.md

Text fallback: https://denson.github.io/colorado-weed-field-guide/plants/cheatgrass/index.md.txt

Agent entry: https://denson.github.io/colorado-weed-field-guide/start.md

Provenance: https://denson.github.io/colorado-weed-field-guide/provenance.json