---
{
  "id": "tansy-ragwort",
  "name": "Tansy ragwort",
  "scientific": "Jacobaea vulgaris",
  "category": "invasive",
  "status": "Colorado noxious weed · List A — Eradicate",
  "status_sources": [
    "CO-rules-2025"
  ],
  "warning": "Poisonous to livestock; harmful alkaloids",
  "warning_tone": "danger",
  "aliases": [
    "Senecio jacobaea"
  ],
  "taxonomy_note": "This is not common tansy or common groundsel. The attempted NC State Jacobaea URL returned a common-groundsel account and was excluded as mismatched evidence.",
  "source_ids": [
    "CO-rules-2025",
    "WA-tansy-ragwort",
    "S27",
    "A-ragwort",
    "Fremont-list-definitions"
  ],
  "description": "Tansy ragwort: Poisonous to livestock; harmful alkaloids. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "WA-tansy-ragwort"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "tansy-ragwort-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "WA-tansy-ragwort"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "tansy-ragwort-2"
    },
    {
      "label": "People",
      "sources": [
        "WA-tansy-ragwort"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "tansy-ragwort-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [
        "A-ragwort",
        "WA-tansy-ragwort"
      ],
      "scope": "Historical genus-group warning; species-specific alkaloid evidence",
      "note": "",
      "id": "tansy-ragwort-4"
    },
    {
      "label": "Other animals",
      "sources": [
        "WA-tansy-ragwort"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "tansy-ragwort-5"
    },
    {
      "id": "tansy-ragwort-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": [
          "tansy-ragwort-3"
        ]
      },
      {
        "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/tansy-ragwort.md"
}
---

# Tansy ragwort

*Jacobaea vulgaris*

**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).

> **Poisonous to livestock; harmful alkaloids.** [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

**Identification caveat:** This is not common tansy or common groundsel. The attempted NC State Jacobaea URL returned a common-groundsel account and was excluded as mismatched evidence.

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

This is a sourced working profile. Evidence is incomplete for **People**. 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.

![Jacobaea vulgaris: An upright flowering plant with yellow heads and deeply divided leaves.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-a-photos-jacobaea-vulgaris-1.jpg)

**flowering habit** — An upright flowering plant with yellow heads and deeply divided leaves.

Photo: jamie-aa; [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/); [source record](https://www.inaturalist.org/observations/126244220); [original image](https://inaturalist-open-data.s3.amazonaws.com/photos/214180355/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. 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.

![Jacobaea vulgaris: Close view of yellow ray florets and central disks on several heads.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-a-photos-jacobaea-vulgaris-2.jpg)

**flower heads** — Close view of yellow ray florets and central disks on several heads.

Photo: jamie-aa; [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/); [source record](https://www.inaturalist.org/observations/126244220); [original image](https://inaturalist-open-data.s3.amazonaws.com/photos/214200970/original.jpeg). Source scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. 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.

![Jacobaea vulgaris: The green undersides and bracts of flower heads viewed from below.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-a-photos-jacobaea-vulgaris-3.jpg)

**head underside** — The green undersides and bracts of flower heads viewed from below.

Photo: jamie-aa; [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/); [source record](https://www.inaturalist.org/observations/126244220); [original image](https://inaturalist-open-data.s3.amazonaws.com/photos/214200978/original.jpeg). Source scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. 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

Ruffled, divided leaves and clusters of yellow daisy-like flowerheads, typically with about thirteen ray flowers. [WA-tansy-ragwort](https://www.nwcb.wa.gov/weeds/tansy-ragwort)

## Plants & habitat

Seed and regrowth spread plants in disturbed fields and pastures. Mowing alone can produce repeated regrowth. [WA-tansy-ragwort](https://www.nwcb.wa.gov/weeds/tansy-ragwort)

## People

All parts contain toxic alkaloids. Do not use the plant in food or home remedies; direct human exposure thresholds are not established here. [WA-tansy-ragwort](https://www.nwcb.wa.gov/weeds/tansy-ragwort)

## Dogs & cats

ASPCA lists Senecio species as toxic to dogs and cats, with liver injury from pyrrolizidine alkaloids. Tansy ragwort was formerly Senecio jacobaea; the ASPCA warning is broader than this species and gives no pet-specific dose. [A-ragwort](https://www.aspca.org/pet-care/aspca-poison-control/toxic-and-non-toxic-plants/ragwort) [WA-tansy-ragwort](https://www.nwcb.wa.gov/weeds/tansy-ragwort)

*Evidence scope: Historical genus-group warning; species-specific alkaloid evidence.*

## Other animals

All parts are poisonous to livestock. Removed or wilted plants can be more palatable; keep cut material and contaminated forage away from animals. [WA-tansy-ragwort](https://www.nwcb.wa.gov/weeds/tansy-ragwort)

## 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-tansy-ragwort** — [Tansy Ragwort](https://www.nwcb.wa.gov/weeds/tansy-ragwort), Washington State Noxious Weed Control Board. Accessed 2026-09-07T01:09:01+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.

- **A-ragwort** — [Ragwort](https://www.aspca.org/pet-care/aspca-poison-control/toxic-and-non-toxic-plants/ragwort), ASPCA Poison Control. Accessed 2026-09-07T01:16:20+00:00. Locator: Species identity, description, ecological and exposure evidence; verify group scope.


[Discuss this plant with the guide](https://denson.github.io/colorado-weed-field-guide/companion/?plant=tansy-ragwort) — 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.
- **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

This is not common tansy or common groundsel. The attempted NC State Jacobaea URL returned a common-groundsel account and was excluded as mismatched evidence.

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 |
|---|---|---|---|---|
| tansy-ragwort-1 | Recognize | Species-specific | WA-tansy-ragwort | No quantitative safe exposure established here. |
| tansy-ragwort-2 | Plants & habitat | Species-specific | WA-tansy-ragwort | No quantitative safe exposure established here. |
| tansy-ragwort-3 | People | Species-specific | WA-tansy-ragwort | No quantitative safe exposure established here. |
| tansy-ragwort-4 | Dogs & cats | Historical genus-group warning; species-specific alkaloid evidence | A-ragwort, WA-tansy-ragwort | No quantitative safe exposure established here. |
| tansy-ragwort-5 | Other animals | Species-specific | WA-tansy-ragwort | 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/tansy-ragwort/

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

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

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