---
{
  "id": "common-cocklebur",
  "name": "Common cocklebur",
  "scientific": "Xanthium strumarium",
  "category": "invasive",
  "status": "Common weed; not an A/B/C listing in the reviewed state rule",
  "status_sources": [
    "CO-rules-2025"
  ],
  "warning": "Burs catch in fur; seedlings and seeds are hazardous",
  "warning_tone": "danger",
  "aliases": [],
  "taxonomy_note": "Xanthium strumarium is treated broadly by some sources and split into other taxa by others. Photographs retain their original source identifications. Native status and a local specimen’s exact taxon need separate review.",
  "source_ids": [
    "CO-rules-2025",
    "N-xanthium-strumarium",
    "S27"
  ],
  "description": "Common cocklebur: Burs catch in fur; seedlings and seeds are hazardous. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "N-xanthium-strumarium"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "common-cocklebur-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "N-xanthium-strumarium"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "common-cocklebur-2"
    },
    {
      "label": "People",
      "sources": [
        "N-xanthium-strumarium"
      ],
      "scope": "Source warning; human clinical detail limited",
      "note": "",
      "id": "common-cocklebur-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [
        "N-xanthium-strumarium"
      ],
      "scope": "Physical-risk inference and general animal warning",
      "note": "",
      "id": "common-cocklebur-4"
    },
    {
      "label": "Other animals",
      "sources": [
        "N-xanthium-strumarium"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "common-cocklebur-5"
    }
  ],
  "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-cocklebur-4"
        ]
      },
      {
        "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"
  },
  "source": "content/plants/common-cocklebur.md"
}
---

# Common cocklebur

*Xanthium strumarium*

**Common weed; not an A/B/C listing in the reviewed state rule.** [CO-rules-2025](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2)

> **Burs catch in fur; seedlings and seeds are hazardous.** [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

**Identification caveat:** Xanthium strumarium is treated broadly by some sources and split into other taxa by others. Photographs retain their original source identifications. Native status and a local specimen’s exact taxon need separate review.

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

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

![Xanthium strumarium: Broad triangular to shallowly lobed leaf with coarse teeth and prominent veins.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-xanthium-strumarium-16-01-leaf.jpg)

**leaf** — Broad triangular to shallowly lobed leaf with coarse teeth and prominent veins.

Photo: Franco Folini; [CC BY 2.5](https://creativecommons.org/licenses/by/2.5); [source record](https://commons.wikimedia.org/wiki/File:Xanthium_strumarium_001.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/5/5d/Xanthium_strumarium_001.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. Cocklebur taxonomy varies by flora and Xanthium strumarium is often used broadly. Related X. orientale-group plants have historically been included. These are source-identified X. strumarium references; one bur is explicitly labeled sensu stricto. General foliage or habit does not independently resolve the complex or establish the identity of Colorado plants. Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Xanthium strumarium: Branching plant with broad petioled leaves and inconspicuous axillary clusters.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-xanthium-strumarium-16-09-habit.jpg)

**habit** — Branching plant with broad petioled leaves and inconspicuous axillary clusters.

Photo: Stan Shebs; [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0); [source record](https://commons.wikimedia.org/wiki/File:Xanthium_strumarium_7.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/7/79/Xanthium_strumarium_7.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. Cocklebur taxonomy varies by flora and Xanthium strumarium is often used broadly. Related X. orientale-group plants have historically been included. These are source-identified X. strumarium references; one bur is explicitly labeled sensu stricto. General foliage or habit does not independently resolve the complex or establish the identity of Colorado plants. Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Xanthium strumarium: Dry oval cocklebur with hooked spines and terminal beaks, photographed with a scale.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-xanthium-strumarium-16-11-bur.jpg)

**bur** — Dry oval cocklebur with hooked spines and terminal beaks, photographed with a 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:Xanthium_strumarium_s._str._sl3.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/2/29/Xanthium_strumarium_s._str._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. Cocklebur taxonomy varies by flora and Xanthium strumarium is often used broadly. Related X. orientale-group plants have historically been included. These are source-identified X. strumarium references; one bur is explicitly labeled sensu stricto. General foliage or habit does not independently resolve the complex or establish the identity of Colorado plants. 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 summer annual with rough, broad leaves and hard burs covered in hooked prickles. [N-xanthium-strumarium](https://plants.ces.ncsu.edu/plants/xanthium-strumarium/)

## Plants & habitat

Can form colonies in fields and wet disturbed ground. Hooked burs move on animals and clothing. [N-xanthium-strumarium](https://plants.ces.ncsu.edu/plants/xanthium-strumarium/)

## People

NC State flags human poisoning but provides primarily animal clinical descriptions. Do not infer a human dose or identical symptoms. [N-xanthium-strumarium](https://plants.ces.ncsu.edu/plants/xanthium-strumarium/)

*Evidence scope: Source warning; human clinical detail limited.*

## Dogs & cats

Burs attach to fur and can cause contact problems. Animal ingestion warnings do not establish dog- or cat-specific thresholds; prevent chewing seedlings, seeds and burs. [N-xanthium-strumarium](https://plants.ces.ncsu.edu/plants/xanthium-strumarium/)

*Evidence scope: Physical-risk inference and general animal warning.*

## Other animals

Seedling cotyledons and seeds are the principal ingestion concern. The source describes low blood sugar, weakness, spasms and potentially fatal poisoning. [N-xanthium-strumarium](https://plants.ces.ncsu.edu/plants/xanthium-strumarium/)

## 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.
- **N-xanthium-strumarium** — [xanthium strumarium — Plant Toolbox](https://plants.ces.ncsu.edu/plants/xanthium-strumarium/), NC State Extension. Accessed 2026-09-07T01:04:56+00:00. Locator: Description; Attributes; Problems; Poisonous to Humans.
- **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=common-cocklebur) — 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.
- **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

Xanthium strumarium is treated broadly by some sources and split into other taxa by others. Photographs retain their original source identifications. Native status and a local specimen’s exact taxon need separate review.

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 |
|---|---|---|---|---|
| common-cocklebur-1 | Recognize | Species-specific | N-xanthium-strumarium | No quantitative safe exposure established here. |
| common-cocklebur-2 | Plants & habitat | Species-specific | N-xanthium-strumarium | No quantitative safe exposure established here. |
| common-cocklebur-3 | People | Source warning; human clinical detail limited | N-xanthium-strumarium | No quantitative safe exposure established here. |
| common-cocklebur-4 | Dogs & cats | Physical-risk inference and general animal warning | N-xanthium-strumarium | No quantitative safe exposure established here. |
| common-cocklebur-5 | Other animals | Species-specific | N-xanthium-strumarium | 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).


---
Canonical HTML: https://denson.github.io/colorado-weed-field-guide/plants/common-cocklebur/

Content revised: 2026-09-07T02:43:00Z

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

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