---
{
  "id": "prostrate-knotweed",
  "name": "Prostrate knotweed",
  "scientific": "Polygonum aviculare",
  "category": "invasive",
  "status": "Common introduced weed · not on state Lists A/B/C",
  "status_sources": [
    "C-floristic-2020",
    "CO-rules-2025"
  ],
  "warning": "A mat-forming weed of compacted ground",
  "warning_tone": "caution",
  "aliases": [
    "knotgrass",
    "wiregrass"
  ],
  "taxonomy_note": "This small lawn weed is not Japanese knotweed or another large invasive Reynoutria species. Polygonum aviculare is treated broadly here. The flower photo is source-labeled Polygonum aviculare subsp. depressum (s. lat.). Segregate-taxon boundaries remain under research; no subspecies determination is made for Colorado specimens.",
  "source_ids": [
    "C-floristic-2020",
    "CO-rules-2025",
    "N-polygonum-aviculare",
    "C-descriptions",
    "S27"
  ],
  "description": "Prostrate knotweed: A mat-forming weed of compacted ground. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Identification",
      "sources": [
        "N-polygonum-aviculare"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "prostrate-knotweed-1"
    },
    {
      "label": "People",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "prostrate-knotweed-2"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "prostrate-knotweed-3"
    },
    {
      "label": "Other animals",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "prostrate-knotweed-4"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "N-polygonum-aviculare"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "prostrate-knotweed-5"
    },
    {
      "label": "Management & timing",
      "sources": [
        "N-polygonum-aviculare",
        "C-descriptions"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "prostrate-knotweed-6"
    }
  ],
  "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": [
          "prostrate-knotweed-2"
        ]
      },
      {
        "area": "Dogs & cats",
        "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.",
        "related_claim_ids": [
          "prostrate-knotweed-3"
        ]
      },
      {
        "area": "Other animals",
        "question": "Clarify feeding and exposure risks for each animal group; do not transfer findings between species.",
        "related_claim_ids": [
          "prostrate-knotweed-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"
  },
  "colorado_relevance": {
    "source_id": "C-floristic-2020",
    "locator": "Appendix B; PDF page 73; Polygonum aviculare",
    "basis": "Included in the 2020 statewide flora assessment. This is not a current county abundance survey.",
    "source_taxon": "Polygonum aviculare"
  },
  "source": "content/plants/prostrate-knotweed.md"
}
---

# Prostrate knotweed

*Polygonum aviculare*

**Common introduced weed · not on state Lists A/B/C.** [C-floristic-2020](https://cnhp.colostate.edu/download/documents/2020/CO_FQA_2020_Final_Report.pdf) [CO-rules-2025](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2)

> **A mat-forming weed of compacted ground.** [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

**Identification caveat:** This small lawn weed is not Japanese knotweed or another large invasive Reynoutria species. Polygonum aviculare is treated broadly here. The flower photo is source-labeled Polygonum aviculare subsp. depressum (s. lat.). Segregate-taxon boundaries remain under research; no subspecies determination is made for Colorado specimens.

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

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

Source-identified reference photographs; these are not a complete identification key. A source location outside Colorado does not establish local occurrence.

![Prostrate knotweed: a flattened mat of branching stems and small leaves spreads across bare soil.](https://denson.github.io/colorado-weed-field-guide/assets/photos/coverage-garden-photos-polygonum-aviculare-04-04-habit.jpg)

**habit** — A flattened mat of branching stems and small leaves spreads across bare soil.

Photo: Rasbak; [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0); [source record](https://commons.wikimedia.org/wiki/File:Polygonum_aviculare,_Gewoon_varkensgras_plant.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/2/20/Polygonum_aviculare%2C_Gewoon_varkensgras_plant.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. Polygonum aviculare is used as a variable species aggregate. The selected flower macro is explicitly source-labeled P. aviculare subsp. depressum (s. lat.); it is retained with that source wording. These photographs do not resolve every segregate taxon or the subspecies of an unknown Colorado specimen. Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.

![Prostrate knotweed: narrow alternate leaves and pale papery sheaths encircle the joints of a slender stem.](https://denson.github.io/colorado-weed-field-guide/assets/photos/coverage-garden-photos-polygonum-aviculare-04-20-leaf-stem.jpg)

**leaf-stem** — Narrow alternate leaves and pale papery sheaths encircle the joints of a slender stem.

Photo: Matt Lavin; [CC BY-SA 2.0](https://creativecommons.org/licenses/by-sa/2.0); [source record](https://commons.wikimedia.org/wiki/File:Polygonum_aviculare_(5143717459).jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/c/cd/Polygonum_aviculare_%285143717459%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. Polygonum aviculare is used as a variable species aggregate. The selected flower macro is explicitly source-labeled P. aviculare subsp. depressum (s. lat.); it is retained with that source wording. These photographs do not resolve every segregate taxon or the subspecies of an unknown Colorado specimen. Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.

![Prostrate knotweed: tiny pale five-parted flowers and young leaves cluster at the stem joints, photographed with a 5 mm scale.](https://denson.github.io/colorado-weed-field-guide/assets/photos/coverage-garden-photos-polygonum-aviculare-04-24-flower.jpg)

**flower** — Tiny pale five-parted flowers and young leaves cluster at the stem joints, photographed with 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:Polygonum_aviculare_subsp._depressum_(s._lat.)_sl8.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/2/28/Polygonum_aviculare_subsp._depressum_%28s._lat.%29_sl8.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. Polygonum aviculare is used as a variable species aggregate. The selected flower macro is explicitly source-labeled P. aviculare subsp. depressum (s. lat.); it is retained with that source wording. These photographs do not resolve every segregate taxon or the subspecies of an unknown Colorado specimen. Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.


## Identification

Look for wiry, low stems, alternating small leaves and papery sheaths around the swollen joints. Tiny flowers appear where the leaves meet the stems. [N-polygonum-aviculare](https://plants.ces.ncsu.edu/plants/polygonum-aviculare/)

## People

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for people. Missing evidence does not establish safety.

## Dogs & cats

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for dogs or cats. Missing evidence does not establish safety.

## Other animals

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for livestock. Missing evidence does not establish safety.

## Plants & habitat

It tolerates trampling, poor soil and pavement cracks. A persistent seed supply helps it return where desirable vegetation struggles. [N-polygonum-aviculare](https://plants.ces.ncsu.edu/plants/polygonum-aviculare/)

## Management & timing

Mowing misses much of this low plant. Address compaction in affected turf and remove small plants before seed production. [N-polygonum-aviculare](https://plants.ces.ncsu.edu/plants/polygonum-aviculare/) [C-descriptions](https://extension.colostate.edu/resource/weed-descriptions/)

## 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

- **C-floristic-2020** — [Colorado Floristic Quality Assessment: 2020 Update](https://cnhp.colostate.edu/download/documents/2020/CO_FQA_2020_Final_Report.pdf), Colorado Natural Heritage Program, Colorado State University. Accessed 2026-09-07T02:27:33+00:00. Locator: Appendix B, Colorado species list: scientific name and native/non-native fields.
- **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-polygonum-aviculare** — [Polygonum aviculare](https://plants.ces.ncsu.edu/plants/polygonum-aviculare/), NC State Extension. Accessed 2026-09-07T02:23:11+00:00. Locator: Description, identification attributes and plant problems; toxicity section where present.
- **C-descriptions** — [Weed descriptions](https://extension.colostate.edu/resource/weed-descriptions/), Colorado State University Extension. Accessed 2026-09-07T00:24:02+00:00. Locator: Species entries.
- **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=prostrate-knotweed) — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.

# Appendix for agents

Colorado inclusion: [C-floristic-2020](https://cnhp.colostate.edu/download/documents/2020/CO_FQA_2020_Final_Report.pdf), Appendix B; PDF page 73; Polygonum aviculare. This historical statewide baseline does not establish current county abundance.

## Open research questions

- **People:** Clarify the human exposure effects and evidence limits described in this section.
- **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.


## Identity and evidence boundaries

This small lawn weed is not Japanese knotweed or another large invasive Reynoutria species. Polygonum aviculare is treated broadly here. The flower photo is source-labeled Polygonum aviculare subsp. depressum (s. lat.). Segregate-taxon boundaries remain under research; no subspecies determination is made for Colorado specimens.

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 |
|---|---|---|---|---|
| prostrate-knotweed-1 | Identification | Species-specific | N-polygonum-aviculare | No quantitative safe exposure established here. |
| prostrate-knotweed-2 | People | Review limitation | Review limitation | No quantitative safe exposure established here. |
| prostrate-knotweed-3 | Dogs & cats | Review limitation | Review limitation | No quantitative safe exposure established here. |
| prostrate-knotweed-4 | Other animals | Review limitation | Review limitation | No quantitative safe exposure established here. |
| prostrate-knotweed-5 | Plants & habitat | Species-specific | N-polygonum-aviculare | No quantitative safe exposure established here. |
| prostrate-knotweed-6 | Management & timing | Species-specific | N-polygonum-aviculare, C-descriptions | 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/prostrate-knotweed/

Content revised: 2026-09-07T02:46:00Z

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

Text fallback: https://denson.github.io/colorado-weed-field-guide/plants/prostrate-knotweed/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