---
{
  "id": "common-teasel",
  "name": "Common teasel",
  "scientific": "Dipsacus fullonum",
  "category": "invasive",
  "status": "Colorado noxious weed · List B — Stop the spread",
  "status_sources": [
    "J-teasel"
  ],
  "warning": "Prickly heads; prolific seed spread",
  "warning_tone": "caution",
  "aliases": [],
  "taxonomy_note": "The Colorado county designation is for Dipsacus spp. This page illustrates source-identified D. fullonum; cutleaf teasel, D. laciniatus, requires a separate identification.",
  "source_ids": [
    "J-teasel",
    "Fremont-list-definitions"
  ],
  "description": "Common teasel: Prickly heads; prolific seed spread. Colorado identification, habitat and exposure evidence.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "J-teasel"
      ],
      "scope": "Dipsacus group; source-identified photo examples",
      "note": "",
      "id": "common-teasel-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "J-teasel"
      ],
      "scope": "Dipsacus group",
      "note": "",
      "id": "common-teasel-2"
    },
    {
      "label": "People",
      "sources": [
        "J-teasel"
      ],
      "scope": "Physical-risk inference",
      "note": "",
      "id": "common-teasel-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [
        "J-teasel"
      ],
      "scope": "Physical-risk inference; toxicity gap",
      "note": "",
      "id": "common-teasel-4"
    },
    {
      "label": "Other animals",
      "sources": [],
      "scope": "Review limitation",
      "note": "Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources.",
      "id": "common-teasel-5"
    },
    {
      "id": "common-teasel-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": "Dogs & cats",
        "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.",
        "related_claim_ids": [
          "common-teasel-4"
        ]
      },
      {
        "area": "Other animals",
        "question": "Clarify feeding and exposure risks for each animal group; do not transfer findings between species.",
        "related_claim_ids": [
          "common-teasel-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/common-teasel.md"
}
---

# Common teasel

*Dipsacus fullonum*

**Colorado noxious weed · List B — Stop the spread.** [J-teasel](https://www.jeffco.us/2152/Teasel)

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).

> **Prickly heads; prolific seed spread.** 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:** The Colorado county designation is for Dipsacus spp. This page illustrates source-identified D. fullonum; cutleaf teasel, D. laciniatus, requires a separate identification.

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

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

![Dipsacus fullonum: Tall erect teasel stem with opposite leaves and branching upper flower-head stalks.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-dipsacus-fullonum-habit.jpg)

**habit** — Tall erect teasel stem with opposite leaves and branching upper flower-head stalks.

Photo: Isidre blanc; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:DIPSACUS_FULLONUM_-_LLANERA_-_IB-822_(Card%C3%B3).JPG); [original image](https://upload.wikimedia.org/wikipedia/commons/3/31/DIPSACUS_FULLONUM_-_LLANERA_-_IB-822_%28Card%C3%B3%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.  Common teasel is also recorded as Dipsacus sylvestris. Do not transfer the identification to cutleaf teasel (D. laciniatus) or cultivated fuller's teasel (D. sativus) without checking diagnostic features. Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Dipsacus fullonum: Egg-shaped prickly head with a horizontal band of lilac flowers and long curved basal bracts.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-dipsacus-fullonum-flower.jpg)

**flower** — Egg-shaped prickly head with a horizontal band of lilac flowers and long curved basal bracts.

Photo: Isidre blanc; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:DIPSACUS_FULLONUM_-_LLANERA_-_IB-083_(Card%C3%B3).JPG); [original image](https://upload.wikimedia.org/wikipedia/commons/6/6f/DIPSACUS_FULLONUM_-_LLANERA_-_IB-083_%28Card%C3%B3%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.  Common teasel is also recorded as Dipsacus sylvestris. Do not transfer the identification to cutleaf teasel (D. laciniatus) or cultivated fuller's teasel (D. sativus) without checking diagnostic features. Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Dipsacus fullonum: Opposite leaves join around a prickly stem to form a water-holding cup.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-dipsacus-fullonum-leaf-stem.jpg)

**leaf-stem** — Opposite leaves join around a prickly stem to form a water-holding cup.

Photo: Björn Appel; [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0/); [source record](https://commons.wikimedia.org/wiki/File:Dipsacus-fullonum-water-storage.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/7/78/Dipsacus-fullonum-water-storage.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.  Common teasel is also recorded as Dipsacus sylvestris. Do not transfer the identification to cutleaf teasel (D. laciniatus) or cultivated fuller's teasel (D. sativus) without checking diagnostic features. 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

Prickly oval heads above stems with paired leaves that form cups. The county’s teasel account describes purple or white flowers and curved bracts. [J-teasel](https://www.jeffco.us/2152/Teasel)

*Evidence scope: Dipsacus group; source-identified photo examples.*

## Plants & habitat

Introduced teasels spread by seed in disturbed areas and ditch banks. Remove rosettes or flowering heads before seed dispersal and monitor for new plants. [J-teasel](https://www.jeffco.us/2152/Teasel)

*Evidence scope: Dipsacus group.*

## People

Prickly heads and stems present a handling hazard; gloves are a practical precaution. [J-teasel](https://www.jeffco.us/2152/Teasel)

*Evidence scope: Physical-risk inference.*

## Dogs & cats

Prickly dried material may injure paws or mouths. Chemical toxicity has not been established here. [J-teasel](https://www.jeffco.us/2152/Teasel)

*Evidence scope: Physical-risk inference; toxicity gap.*

## Other animals

Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources. 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-teasel** — [Teasel](https://www.jeffco.us/2152/Teasel), Jefferson County, Colorado. Accessed 2026-09-07T00:27:26+00:00. Locator: Description, impacts, Colorado list designation, management.


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

# Appendix for agents

## Open research questions

- **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

The Colorado county designation is for Dipsacus spp. This page illustrates source-identified D. fullonum; cutleaf teasel, D. laciniatus, requires a separate identification.

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 |
|---|---|---|---|---|
| common-teasel-1 | Recognize | Dipsacus group; source-identified photo examples | J-teasel | No quantitative exposure threshold established here. |
| common-teasel-2 | Plants & habitat | Dipsacus group | J-teasel | No quantitative exposure threshold established here. |
| common-teasel-3 | People | Physical-risk inference | J-teasel | No quantitative exposure threshold established here. |
| common-teasel-4 | Dogs & cats | Physical-risk inference; toxicity gap | J-teasel | No quantitative exposure threshold established here. |
| common-teasel-5 | Other animals | Review limitation | Review limitation | Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources. |

## 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/common-teasel/

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

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

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