---
{
  "id": "common-ragweed",
  "name": "Common ragweed",
  "scientific": "Ambrosia artemisiifolia",
  "category": "native",
  "status": "Colorado native",
  "status_sources": [
    "N-ambrosia-artemisiifolia"
  ],
  "warning": "Pollen allergy; skin irritation",
  "warning_tone": "caution",
  "aliases": [
    "hay fever weed"
  ],
  "taxonomy_note": "",
  "source_ids": [
    "N-ambrosia-artemisiifolia"
  ],
  "description": "Common ragweed: Pollen allergy; skin irritation. Colorado identification, habitat and exposure evidence.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "N-ambrosia-artemisiifolia"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "common-ragweed-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "N-ambrosia-artemisiifolia"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "common-ragweed-2"
    },
    {
      "label": "People",
      "sources": [
        "N-ambrosia-artemisiifolia"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "common-ragweed-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources.",
      "id": "common-ragweed-4"
    },
    {
      "label": "Other animals",
      "sources": [],
      "scope": "Review limitation",
      "note": "This review did not establish species-specific livestock toxicity.",
      "id": "common-ragweed-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-ragweed-4"
        ]
      },
      {
        "area": "Other animals",
        "question": "Clarify feeding and exposure risks for each animal group; do not transfer findings between species.",
        "related_claim_ids": [
          "common-ragweed-5"
        ]
      },
      {
        "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-ragweed.md"
}
---

# Common ragweed

*Ambrosia artemisiifolia*

**Colorado native.** [N-ambrosia-artemisiifolia](https://plants.ces.ncsu.edu/plants/ambrosia-artemisiifolia/)

> **Pollen allergy; skin irritation.** Native status, garden use and noxious-weed class are separate from toxicity. [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

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

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

![Ambrosia artemisiifolia: A low stand of common ragweed flowering along the edge of a paved path, with other vegetation nearby.](https://denson.github.io/colorado-weed-field-guide/assets/photos/native-ambrosia-artemisiifolia-1.jpg)

**habit and habitat** — A low stand of common ragweed flowering along the edge of a paved path, with other vegetation nearby.

Photo: Ayotte, Gilles, 1948-; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Ambrosia_artemisiifolia_15-p.bot-ambro.arte-49.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/b/b3/Ambrosia_artemisiifolia_15-p.bot-ambro.arte-49.jpg). Wikimedia Commons source file title and species metadata identify the taxon. Visible morphology was checked for consistency, not treated as an independent botanical determination.   No edits to the downloaded image. Wikimedia may have supplied a scaled thumbnail; original and download URLs are recorded separately. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Ambrosia artemisiifolia: Several deeply divided green ragweed leaves viewed from above.](https://denson.github.io/colorado-weed-field-guide/assets/photos/native-ambrosia-artemisiifolia-2.jpg)

**leaves** — Several deeply divided green ragweed leaves viewed from above.

Photo: Meneerke bloem; [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0); [source record](https://commons.wikimedia.org/wiki/File:Ambrosia_artemisiifolia_leaf.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/c/c9/Ambrosia_artemisiifolia_leaf.jpg). Wikimedia Commons source file title and species metadata identify the taxon. Visible morphology was checked for consistency, not treated as an independent botanical determination.   No edits to the downloaded image. Wikimedia may have supplied a scaled thumbnail; original and download URLs are recorded separately. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Ambrosia artemisiifolia: Close view of a terminal raceme of small green male flower heads; the source photo includes a 5 mm scale.](https://denson.github.io/colorado-weed-field-guide/assets/photos/native-ambrosia-artemisiifolia-3.jpg)

**flower detail** — Close view of a terminal raceme of small green male flower heads; the source photo includes a 5 mm 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:Ambrosia_artemisiifolia_sl6.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/e/e7/Ambrosia_artemisiifolia_sl6.jpg). Wikimedia Commons source file title and species metadata identify the taxon. Visible morphology was checked for consistency, not treated as an independent botanical determination.   No edits to the downloaded image. Wikimedia may have supplied a scaled thumbnail; original and download URLs are recorded separately. Gallery display preserves the full image; the catalog preview uses a CSS crop.


## Recognize

An annual with deeply divided, fern-like leaves and inconspicuous green flower spikes. [N-ambrosia-artemisiifolia](https://plants.ces.ncsu.edu/plants/ambrosia-artemisiifolia/)

## Plants & habitat

A dry-site volunteer that produces many persistent seeds; birds eat its seeds. Remove unwanted plants before flowering and seed set. [N-ambrosia-artemisiifolia](https://plants.ces.ncsu.edu/plants/ambrosia-artemisiifolia/)

## People

Windborne pollen is a major cause of hay fever; contact dermatitis is also reported. [N-ambrosia-artemisiifolia](https://plants.ces.ncsu.edu/plants/ambrosia-artemisiifolia/)

## 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

This review did not establish species-specific livestock toxicity. 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

- **N-ambrosia-artemisiifolia** — [Ambrosia artemisiifolia — Plant Toolbox](https://plants.ces.ncsu.edu/plants/ambrosia-artemisiifolia/), NC State Extension. Accessed 2026-09-07T00:23:56+00:00. Locator: Description, Attributes, Poisonous to Humans, Problems.


[Discuss this plant with the guide](https://denson.github.io/colorado-weed-field-guide/companion/?plant=common-ragweed) — 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.
- **Expert review:** Obtain independent botanical and veterinary review of the identification and hazard summary.


## Taxon and evidence boundaries

Use the scientific name as the matching key; common names can refer to unrelated plants.

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-ragweed-1 | Recognize | Species-specific | N-ambrosia-artemisiifolia | No quantitative exposure threshold established here. |
| common-ragweed-2 | Plants & habitat | Species-specific | N-ambrosia-artemisiifolia | No quantitative exposure threshold established here. |
| common-ragweed-3 | People | Species-specific | N-ambrosia-artemisiifolia | No quantitative exposure threshold established here. |
| common-ragweed-4 | Dogs & cats | Review limitation | Review limitation | Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources. |
| common-ragweed-5 | Other animals | Review limitation | Review limitation | This review did not establish species-specific livestock toxicity. |

## 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).


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

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

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

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