---
{
  "id": "spotted-knapweed",
  "name": "Spotted knapweed",
  "scientific": "Centaurea stoebe",
  "category": "invasive",
  "status": "Colorado noxious weed · List B — Stop the spread",
  "status_sources": [
    "J-spotted-knapweed"
  ],
  "warning": "Competes with native vegetation",
  "warning_tone": "caution",
  "aliases": [
    "Centaurea maculosa"
  ],
  "taxonomy_note": "Some Colorado references use Centaurea maculosa for spotted knapweed. We retain their name in the citation record and use C. stoebe as the catalog label.",
  "source_ids": [
    "J-spotted-knapweed",
    "C-descriptions",
    "Fremont-list-definitions"
  ],
  "description": "Spotted knapweed: Competes with native vegetation. Colorado identification, habitat and exposure evidence.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "C-descriptions"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "spotted-knapweed-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "J-spotted-knapweed"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "spotted-knapweed-2"
    },
    {
      "label": "People",
      "sources": [],
      "scope": "Review limitation",
      "note": "This review did not establish a species-specific human toxicity profile.",
      "id": "spotted-knapweed-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources.",
      "id": "spotted-knapweed-4"
    },
    {
      "label": "Other animals",
      "sources": [],
      "scope": "Review limitation",
      "note": "Do not transfer Russian-knapweed horse toxicity to spotted knapweed without species-specific evidence.",
      "id": "spotted-knapweed-5"
    },
    {
      "id": "spotted-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": "B",
  "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": [
          "spotted-knapweed-3"
        ]
      },
      {
        "area": "Dogs & cats",
        "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.",
        "related_claim_ids": [
          "spotted-knapweed-4"
        ]
      },
      {
        "area": "Other animals",
        "question": "Clarify feeding and exposure risks for each animal group; do not transfer findings between species.",
        "related_claim_ids": [
          "spotted-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": "B — Stop the spread",
  "source": "content/plants/spotted-knapweed.md"
}
---

# Spotted knapweed

*Centaurea stoebe*

**Colorado noxious weed · List B — Stop the spread.** [J-spotted-knapweed](https://www.jeffco.us/2181/Spotted-Knapweed)

Established in some areas. Requirements vary by location: eradication, containment or suppression to stop further spread. 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).

> **Competes with native vegetation.** Native status, garden use and noxious-weed class are separate from toxicity. [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

**Identification caveat:** Some Colorado references use Centaurea maculosa for spotted knapweed. We retain their name in the citation record and use C. stoebe as the catalog label.

## 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

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.

![Centaurea stoebe: Close view of the purple tubular florets forming a knapweed flower head.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-centaurea-stoebe-flower.jpg)

**flower** — Close view of the purple tubular florets forming a knapweed flower head.

Photo: Alan Vernon; [CC BY 2.0](https://creativecommons.org/licenses/by/2.0); [source record](https://commons.wikimedia.org/wiki/File:Spotted_Knapweed_(Centaurea_maculosa).jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/4/45/Spotted_Knapweed_%28Centaurea_maculosa%29.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.  Spotted knapweed is a species complex; North American invasive plants are often treated as C. stoebe subsp. micranthos. Some source photos retain the historically applied name Centaurea maculosa. Photographs do not establish subspecies or ploidy. Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Centaurea stoebe: Branched slender stems with divided narrow leaves and scattered purple flower heads.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-centaurea-stoebe-habit.jpg)

**habit** — Branched slender stems with divided narrow leaves and scattered purple flower heads.

Photo: Agnieszka Kwiecień, Nova; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Centaurea_stoebe_Chaber_nadre%C5%84ski_2020-07-12_02.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/b/b5/Centaurea_stoebe_Chaber_nadre%C5%84ski_2020-07-12_02.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.  Spotted knapweed is a species complex; North American invasive plants are often treated as C. stoebe subsp. micranthos. Some source photos retain the historically applied name Centaurea maculosa. Photographs do not establish subspecies or ploidy. Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Centaurea stoebe: Flower-head base showing overlapping bracts with dark fringed tips, beside an unopened head.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-centaurea-stoebe-involucral-bracts.jpeg)

**involucral-bracts** — Flower-head base showing overlapping bracts with dark fringed tips, beside an unopened head.

Photo: Kristian Peters -- Fabelfroh 08:50, 2 November 2006 (UTC); [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0/); [source record](https://commons.wikimedia.org/wiki/File:Centaurea_stoebe_huellblaetter.jpeg); [original image](https://upload.wikimedia.org/wikipedia/commons/2/21/Centaurea_stoebe_huellblaetter.jpeg). 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.  Spotted knapweed is a species complex; North American invasive plants are often treated as C. stoebe subsp. micranthos. Some source photos retain the historically applied name Centaurea maculosa. Photographs do not establish subspecies or ploidy. 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

Purple flowerheads with dark-tipped, fringed bracts; a short-lived perennial spreading mainly by seed. [C-descriptions](https://extension.colostate.edu/resource/weed-descriptions/)

## Plants & habitat

An introduced noxious weed. Preventing seed production and maintaining desirable vegetation are parts of long-term control. [J-spotted-knapweed](https://www.jeffco.us/2181/Spotted-Knapweed)

## People

This review did not establish a species-specific human toxicity profile. This is an evidence gap, not proof of safety.

## Dogs & cats

Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources. This is an evidence gap, not proof of safety.

## Other animals

Do not transfer Russian-knapweed horse toxicity to spotted knapweed without species-specific evidence. This is an evidence gap, not proof of safety.

## 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

- **J-spotted-knapweed** — [Spotted Knapweed](https://www.jeffco.us/2181/Spotted-Knapweed), Jefferson County, Colorado. Accessed 2026-09-07T00:27:26+00:00. Locator: Description, impacts, Colorado list designation, management.
- **C-descriptions** — [Weed descriptions](https://extension.colostate.edu/resource/weed-descriptions/), Colorado State University Extension. Accessed 2026-09-07T00:24:02+00:00. Locator: Species entries.


[Discuss this plant with the guide](https://denson.github.io/colorado-weed-field-guide/companion/?plant=spotted-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.


## Taxon and evidence boundaries

Some Colorado references use Centaurea maculosa for spotted knapweed. We retain their name in the citation record and use C. stoebe as the catalog label.

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 |
|---|---|---|---|---|
| spotted-knapweed-1 | Recognize | Species-specific | C-descriptions | No quantitative exposure threshold established here. |
| spotted-knapweed-2 | Plants & habitat | Species-specific | J-spotted-knapweed | No quantitative exposure threshold established here. |
| spotted-knapweed-3 | People | Review limitation | Review limitation | This review did not establish a species-specific human toxicity profile. |
| spotted-knapweed-4 | Dogs & cats | Review limitation | Review limitation | Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources. |
| spotted-knapweed-5 | Other animals | Review limitation | Review limitation | Do not transfer Russian-knapweed horse toxicity to spotted knapweed without species-specific evidence. |

## 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 “B — Stop the spread” 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/spotted-knapweed/

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

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

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