---
{
  "id": "meadow-knapweed",
  "name": "Meadow knapweed",
  "scientific": "Centaurea × moncktonii",
  "category": "invasive",
  "status": "Colorado noxious weed · List A — Eradicate",
  "status_sources": [
    "CO-rules-2025"
  ],
  "warning": "Outcompetes pasture and meadow plants",
  "warning_tone": "caution",
  "aliases": [
    "Centaurea x moncktonii",
    "Centaurea x gerstlaueri"
  ],
  "taxonomy_note": "A hybrid complex associated with C. jacea and C. nigra. Older meadow-knapweed names can represent different taxonomic concepts; records require checking.",
  "source_ids": [
    "CO-rules-2025",
    "WA-meadow-knapweed",
    "S27",
    "Fremont-list-definitions"
  ],
  "description": "Meadow knapweed: Outcompetes pasture and meadow plants. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "WA-meadow-knapweed"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "meadow-knapweed-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "WA-meadow-knapweed"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "meadow-knapweed-2"
    },
    {
      "label": "People",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "meadow-knapweed-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "meadow-knapweed-4"
    },
    {
      "label": "Other animals",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "meadow-knapweed-5"
    },
    {
      "id": "meadow-knapweed-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": "A",
  "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": [
          "meadow-knapweed-3"
        ]
      },
      {
        "area": "Dogs & cats",
        "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.",
        "related_claim_ids": [
          "meadow-knapweed-4"
        ]
      },
      {
        "area": "Other animals",
        "question": "Clarify feeding and exposure risks for each animal group; do not transfer findings between species.",
        "related_claim_ids": [
          "meadow-knapweed-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": "A — Eradicate",
  "source": "content/plants/meadow-knapweed.md"
}
---

# Meadow knapweed

*Centaurea × moncktonii*

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

Uncommon in Colorado. All populations are designated for eradication statewide. 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).

> **Outcompetes pasture and meadow plants.** [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

**Identification caveat:** A hybrid complex associated with C. jacea and C. nigra. Older meadow-knapweed names can represent different taxonomic concepts; records require checking.

## 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.

![Centaurea × moncktonii: A purple flower head among additional buds and spent heads.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-a-photos-centaurea-x-moncktonii-1.jpg)

**flowers** — A purple flower head among additional buds and spent heads.

Photo: Eric Coombs, Oregon Department of Agriculture, Bugwood.org; [CC BY 3.0 us](https://creativecommons.org/licenses/by/3.0/us/deed.en); [source record](https://commons.wikimedia.org/wiki/File:Centaurea_%C3%97_moncktonii_5435714.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/1/11/Centaurea_%C3%97_moncktonii_5435714.jpg). Source scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. This is the source-identified hybrid meadow knapweed (C. jacea × C. nigra). The complex overlaps morphologically; the photographs do not independently establish hybrid ancestry. 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.

![Centaurea × moncktonii: A flowering head and a spent head held to show the dark involucral bracts.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-a-photos-centaurea-x-moncktonii-2.jpg)

**head and bracts** — A flowering head and a spent head held to show the dark involucral bracts.

Photo: Zihao Wang; [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/); [source record](https://www.inaturalist.org/observations/14803189); [original image](https://inaturalist-open-data.s3.amazonaws.com/photos/22096242/original.jpg). Source scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. This is the source-identified hybrid meadow knapweed (C. jacea × C. nigra). The complex overlaps morphologically; the photographs do not independently establish hybrid ancestry. iNaturalist large server-resized image; no local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Centaurea × moncktonii: A slender upright stem with narrow, alternate leaves.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-a-photos-centaurea-x-moncktonii-3.jpg)

**stem leaves** — A slender upright stem with narrow, alternate leaves.

Photo: Zihao Wang; [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/); [source record](https://www.inaturalist.org/observations/14803189); [original image](https://inaturalist-open-data.s3.amazonaws.com/photos/22096211/original.jpg). Source scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. This is the source-identified hybrid meadow knapweed (C. jacea × C. nigra). The complex overlaps morphologically; the photographs do not independently establish hybrid ancestry. iNaturalist large server-resized image; no local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.


## Recognize

A variable perennial hybrid with mostly undivided leaves and purple to white flowerheads. Brown, papery, fringed flowerhead bracts help distinguish it. [WA-meadow-knapweed](https://www.nwcb.wa.gov/weeds/meadow-knapweed)

## Plants & habitat

Spreads through seed and regrowth from root crowns, replacing desirable forage and native meadow vegetation. [WA-meadow-knapweed](https://www.nwcb.wa.gov/weeds/meadow-knapweed)

## 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/)

This is a statewide eradication priority. Contact your county weed program promptly for identification and an approved management and disposal plan. [CO-rules-2025](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2)

## 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.
- **WA-meadow-knapweed** — [Meadow Knapweed](https://www.nwcb.wa.gov/weeds/meadow-knapweed), 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](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=meadow-knapweed) — 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

A hybrid complex associated with C. jacea and C. nigra. Older meadow-knapweed names can represent different taxonomic concepts; records require checking.

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 |
|---|---|---|---|---|
| meadow-knapweed-1 | Recognize | Species-specific | WA-meadow-knapweed | No quantitative safe exposure established here. |
| meadow-knapweed-2 | Plants & habitat | Species-specific | WA-meadow-knapweed | No quantitative safe exposure established here. |
| meadow-knapweed-3 | People | Review limitation | Review limitation | No quantitative safe exposure established here. |
| meadow-knapweed-4 | Dogs & cats | Review limitation | Review limitation | No quantitative safe exposure established here. |
| meadow-knapweed-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 “A — Eradicate” 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/meadow-knapweed/

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

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

Text fallback: https://denson.github.io/colorado-weed-field-guide/plants/meadow-knapweed/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