---
{
  "id": "common-yarrow",
  "name": "Common yarrow",
  "scientific": "Achillea millefolium",
  "category": "xeriscape",
  "status": "Low-water garden plant",
  "status_sources": [
    "S03",
    "S07"
  ],
  "warning": "Toxic to pets · Skin irritation",
  "warning_tone": "danger",
  "aliases": [],
  "taxonomy_note": "",
  "source_ids": [
    "S03",
    "S07",
    "S08"
  ],
  "description": "Common yarrow: Toxic to pets · Skin irritation. Colorado identification, habitat and exposure evidence.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "S07"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "common-yarrow-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "S07"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "common-yarrow-2"
    },
    {
      "label": "People",
      "sources": [
        "S07"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "common-yarrow-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [
        "S08"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "common-yarrow-4"
    },
    {
      "label": "Other animals",
      "sources": [
        "S08"
      ],
      "scope": "Species-specific",
      "note": "",
      "reviewed": "2026-09-06",
      "id": "common-yarrow-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": "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-yarrow.md"
}
---

# Common yarrow

*Achillea millefolium*

**Low-water garden plant.** [S03](https://www.extension.colostate.edu/docs/pubs/native/FrontRangeSm.pdf) [S07](https://plants.ces.ncsu.edu/plants/achillea-millefolium/)

> **Toxic to pets · 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. The cited findings are available 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.

![White flower-head cluster viewed from above, with individual ray and disk florets visible.](https://denson.github.io/colorado-weed-field-guide/assets/photos/xeriscape-achillea-millefolium-02.jpg)

**flower** — White flower-head cluster viewed from above, with individual ray and disk florets visible.

Photo: Petar Milošević; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Yarrow_(Achillea_millefolium).jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/1/17/Yarrow_%28Achillea_millefolium%29.jpg). Source-supported identification with visual consistency check Photo selection verifies source labeling and visible consistency; it is not an independent specimen determination.  Downloaded source thumbnail; no further pixel edits. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Upright flowering yarrow stems with white flat-topped clusters growing among grasses.](https://denson.github.io/colorado-weed-field-guide/assets/photos/xeriscape-achillea-millefolium-12.jpg)

**habit** — Upright flowering yarrow stems with white flat-topped clusters growing among grasses.

Photo: Daniel VILLAFRUELA .; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Achillea_millefolium-Achill%C3%A9e_millefeuille-20190726.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/2/2e/Achillea_millefolium-Achill%C3%A9e_millefeuille-20190726.jpg). Source-supported identification with visual consistency check Photo selection verifies source labeling and visible consistency; it is not an independent specimen determination.  Downloaded source thumbnail; no further pixel edits. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Finely divided, featherlike yarrow leaves along a hairy stem.](https://denson.github.io/colorado-weed-field-guide/assets/photos/xeriscape-achillea-millefolium-13.jpg)

**leaf** — Finely divided, featherlike yarrow leaves along a hairy stem.

Photo: Alpsdake; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Achillea_millefolium_(leaf).jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/5/5b/Achillea_millefolium_%28leaf%29.jpg). Source-supported identification with visual consistency check Photo selection verifies source labeling and visible consistency; it is not an independent specimen determination.  Downloaded source thumbnail; no further pixel edits. Gallery display preserves the full image; the catalog preview uses a CSS crop.


## Recognize

Finely divided, fernlike leaves and flat-topped clusters of small flowers. Native range includes North America, Europe, and Asia; cultivated forms vary. [S07](https://plants.ces.ncsu.edu/plants/achillea-millefolium/)

## Plants & habitat

Tolerates drought and feeds pollinators, but can spread aggressively through underground stems and seed. [S07](https://plants.ces.ncsu.edu/plants/achillea-millefolium/)

## People

Contact can cause dermatitis. Gloves reduce skin contact during garden work. [S07](https://plants.ces.ncsu.edu/plants/achillea-millefolium/)

## Dogs & cats

Toxic to dogs and cats. Reported signs include vomiting, diarrhea, drooling, and dermatitis. [S08](https://www.aspca.org/pet-care/aspca-poison-control/toxic-and-non-toxic-plants/yarrow)

## Other animals

Also toxic to horses. ASPCA includes colic among reported signs; do not infer safety for other livestock. [S08](https://www.aspca.org/pet-care/aspca-poison-control/toxic-and-non-toxic-plants/yarrow)

## 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

- **S03** — [Low-Water Native Plants for Colorado Gardens: Front Range & Foothills](https://www.extension.colostate.edu/docs/pubs/native/FrontRangeSm.pdf), Colorado Native Plant Society / CSU Extension. Accessed 2026-09-07T00:23:53+00:00. Locator: Plant table: Asclepias speciosa and Achillea millefolium.
- **S07** — [Achillea millefolium](https://plants.ces.ncsu.edu/plants/achillea-millefolium/), NC State Extension · Plant Toolbox. Accessed 2026-09-07T00:23:53+00:00. Locator: Description; Problems; Wildlife Value.
- **S08** — [Yarrow](https://www.aspca.org/pet-care/aspca-poison-control/toxic-and-non-toxic-plants/yarrow), ASPCA Poison Control. Accessed 2026-09-07T00:23:53+00:00. Locator: Scientific Name; Toxicity; Clinical Signs.


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

# Appendix for agents

## Open research questions

- **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-yarrow-1 | Recognize | Species-specific | S07 | No quantitative exposure threshold established here. |
| common-yarrow-2 | Plants & habitat | Species-specific | S07 | No quantitative exposure threshold established here. |
| common-yarrow-3 | People | Species-specific | S07 | No quantitative exposure threshold established here. |
| common-yarrow-4 | Dogs & cats | Species-specific | S08 | No quantitative exposure threshold established here. |
| common-yarrow-5 | Other animals | Species-specific | S08 | No quantitative exposure threshold established here. |

## 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-yarrow/

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

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

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