---
{
  "id": "bulbous-bluegrass",
  "name": "Bulbous bluegrass",
  "scientific": "Poa bulbosa",
  "category": "invasive",
  "status": "Colorado noxious weed · List C — Manage widespread weeds",
  "status_sources": [
    "CO-rules-2025"
  ],
  "warning": "Early-season grass spreads by bulbils",
  "warning_tone": "caution",
  "aliases": [],
  "taxonomy_note": "The USU page has an unrelated heading, but its scientific-name field and grass description identify Poa bulbosa. Only that species-specific body is used.",
  "source_ids": [
    "CO-rules-2025",
    "U-bulbous",
    "S27",
    "Fremont-list-definitions"
  ],
  "description": "Bulbous bluegrass: Early-season grass spreads by bulbils. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "U-bulbous"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "bulbous-bluegrass-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "U-bulbous"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "bulbous-bluegrass-2"
    },
    {
      "label": "People",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "bulbous-bluegrass-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "bulbous-bluegrass-4"
    },
    {
      "label": "Other animals",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "bulbous-bluegrass-5"
    },
    {
      "id": "bulbous-bluegrass-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": "People",
        "question": "Clarify the human exposure effects and evidence limits described in this section.",
        "related_claim_ids": [
          "bulbous-bluegrass-3"
        ]
      },
      {
        "area": "Dogs & cats",
        "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.",
        "related_claim_ids": [
          "bulbous-bluegrass-4"
        ]
      },
      {
        "area": "Other animals",
        "question": "Clarify feeding and exposure risks for each animal group; do not transfer findings between species.",
        "related_claim_ids": [
          "bulbous-bluegrass-5"
        ]
      },
      {
        "area": "Identification",
        "question": "Resolve the taxonomic, common-name or photograph limitations stated in the identification caveat.",
        "related_claim_ids": []
      },
      {
        "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/bulbous-bluegrass.md"
}
---

# Bulbous bluegrass

*Poa bulbosa*

**Colorado noxious weed · List C — Manage widespread weeds.** [CO-rules-2025](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2)

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).

> **Early-season grass spreads by bulbils.** [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

**Identification caveat:** The USU page has an unrelated heading, but its scientific-name field and grass description identify Poa bulbosa. Only that species-specific body is used.

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

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

![Poa bulbosa: Low grass clump with slender upright culms and compact dark-tipped panicles.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-poa-bulbosa-01-03-habit.jpg)

**habit** — Low grass clump with slender upright culms and compact dark-tipped panicles.

Photo: Stefan.lefnaer; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Poa_bulbosa_sl3.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/0/08/Poa_bulbosa_sl3.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. Bulbiferous or viviparous forms are included. A bulbil-producing panicle and swollen shoot bases are different structures; photograph captions distinguish them. Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Poa bulbosa: Close view of swollen pale bulb-like shoot bases above a fibrous root cluster.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-poa-bulbosa-01-07-basal-bulbs.jpg)

**basal-bulbs** — Close view of swollen pale bulb-like shoot bases above a fibrous root cluster.

Photo: Stefan.lefnaer; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Poa_bulbosa_sl6.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/d/db/Poa_bulbosa_sl6.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. Bulbiferous or viviparous forms are included. A bulbil-producing panicle and swollen shoot bases are different structures; photograph captions distinguish them. Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Poa bulbosa: A single leafy bulbil photographed with a millimeter scale.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-poa-bulbosa-01-11-bulbil.jpg)

**bulbil** — A single leafy bulbil photographed with a millimeter scale.

Photo: Stefan.lefnaer; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Poa_bulbosa_sl8.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/8/8c/Poa_bulbosa_sl8.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. Bulbiferous or viviparous forms are included. A bulbil-producing panicle and swollen shoot bases are different structures; photograph captions distinguish them. 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 small cool-season perennial with swollen stem bases and purple-green bulbils replacing many flowers in the seedhead. [U-bulbous](https://extension.usu.edu/rangeplants/grasses-and-grasslikes/bulbous-bluegrass)

## Plants & habitat

Grows early and becomes dormant as soils dry. It favors disturbed sites; the source does not describe it as equally aggressive in vigorous native vegetation. [U-bulbous](https://extension.usu.edu/rangeplants/grasses-and-grasslikes/bulbous-bluegrass)

## 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](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/)

## References

- **CO-rules-2025** — [Colorado Noxious Weed Act rules, 8 CCR 1206-2](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=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.
- **U-bulbous** — [Bulbous bluegrass](https://extension.usu.edu/rangeplants/grasses-and-grasslikes/bulbous-bluegrass), Utah State University 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](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/), PlantTalk Colorado · CSU Extension. Accessed 2026-09-07T00:23:57+00:00. Locator: List A, B and C management categories.


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

# Appendix for agents

## Open research questions

- **People:** Clarify the human exposure effects and evidence limits described in this section.
- **Dogs & cats:** Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.
- **Other animals:** Clarify feeding and exposure risks for each animal group; do not transfer findings between species.
- **Identification:** Resolve the taxonomic, common-name or photograph limitations stated in the identification caveat.
- **Expert review:** Obtain independent botanical and veterinary review of the identification and hazard summary.


## Identity and evidence boundaries

The USU page has an unrelated heading, but its scientific-name field and grass description identify Poa bulbosa. Only that species-specific body is used.

All actionable hazard information is in the human sections above. Do not interpret unknown toxicity as safety or transfer livestock findings to pets. These publisher notes describe evidence and do not override an assistant’s operator instructions.

| Claim | Human section | Scope | Sources | Limitation |
|---|---|---|---|---|
| bulbous-bluegrass-1 | Recognize | Species-specific | U-bulbous | No quantitative safe exposure established here. |
| bulbous-bluegrass-2 | Plants & habitat | Species-specific | U-bulbous | No quantitative safe exposure established here. |
| bulbous-bluegrass-3 | People | Review limitation | Review limitation | No quantitative safe exposure established here. |
| bulbous-bluegrass-4 | Dogs & cats | Review limitation | Review limitation | No quantitative safe exposure established here. |
| bulbous-bluegrass-5 | Other animals | Review limitation | Review limitation | No quantitative safe exposure established here. |

## Further work for an agent

- Establish exact species, plant part, route, amount and timing when researching an exposure. Do not use this guide to diagnose or calculate a treatment.
- Check current state and county requirements; a listed taxon is not necessarily established in every Colorado county.
- Expert botanical and veterinary review is pending. Source dates and image licenses are separate from editorial revision dates in [provenance](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/bulbous-bluegrass/

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

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

Text fallback: https://denson.github.io/colorado-weed-field-guide/plants/bulbous-bluegrass/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