---
{
  "id": "houndstongue",
  "name": "Houndstongue",
  "scientific": "Cynoglossum officinale",
  "category": "invasive",
  "status": "Colorado noxious weed · List B — Stop the spread",
  "status_sources": [
    "J-houndstongue"
  ],
  "warning": "Toxic to livestock",
  "warning_tone": "danger",
  "aliases": [],
  "taxonomy_note": "",
  "source_ids": [
    "J-houndstongue",
    "Fremont-list-definitions"
  ],
  "description": "Houndstongue: Toxic to livestock. Colorado identification, habitat and exposure evidence.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "J-houndstongue"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "houndstongue-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "J-houndstongue"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "houndstongue-2"
    },
    {
      "label": "People",
      "sources": [],
      "scope": "Review limitation",
      "note": "Species-specific human ingestion effects were not established in the reviewed county source.",
      "id": "houndstongue-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources.",
      "id": "houndstongue-4"
    },
    {
      "label": "Other animals",
      "sources": [
        "J-houndstongue"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "houndstongue-5"
    },
    {
      "id": "houndstongue-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": "People",
        "question": "Clarify the human exposure effects and evidence limits described in this section.",
        "related_claim_ids": [
          "houndstongue-3"
        ]
      },
      {
        "area": "Dogs & cats",
        "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.",
        "related_claim_ids": [
          "houndstongue-4"
        ]
      },
      {
        "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/houndstongue.md"
}
---

# Houndstongue

*Cynoglossum officinale*

**Colorado noxious weed · List B — Stop the spread.** [J-houndstongue](https://www.jeffco.us/2414/Houndstongue)

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).

> **Toxic to livestock.** 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 **People, Dogs & cats**. 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.

![Cynoglossum officinale: Upright leafy flowering plant with broad lance-shaped foliage and branched upper flower stems.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-cynoglossum-officinale-habit.jpg)

**habit** — Upright leafy flowering plant with broad lance-shaped foliage and branched upper flower stems.

Photo: Bernd Haynold; [CC BY 2.5](https://creativecommons.org/licenses/by/2.5); [source record](https://commons.wikimedia.org/wiki/File:Cynoglossum_officinale_190506.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/a/a6/Cynoglossum_officinale_190506.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.   Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Cynoglossum officinale: Small dark red-purple flowers in branching clusters above broad green leaves.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-cynoglossum-officinale-flower.jpg)

**flower** — Small dark red-purple flowers in branching clusters above broad green leaves.

Photo: Robert Flogaus-Faust; [CC BY 4.0](https://creativecommons.org/licenses/by/4.0); [source record](https://commons.wikimedia.org/wiki/File:Cynoglossum_officinale_RF.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/b/b2/Cynoglossum_officinale_RF.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.   Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Cynoglossum officinale: Green bristly nutlets developing among dark purple five-lobed flowers on hairy stems.](https://denson.github.io/colorado-weed-field-guide/assets/photos/invasive-cynoglossum-officinale-fruit.jpg)

**fruit** — Green bristly nutlets developing among dark purple five-lobed flowers on hairy stems.

Photo: Antti Bilund; [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0); [source record](https://commons.wikimedia.org/wiki/File:Cynoglossum_officinale_flowers_fruits_close_up_AB.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/5/58/Cynoglossum_officinale_flowers_fruits_close_up_AB.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.   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

Hairy leaves form a rosette before stems carry small reddish-purple flowers. A biennial or short-lived perennial. [J-houndstongue](https://www.jeffco.us/2414/Houndstongue)

## Plants & habitat

Introduced from Eurasia; spreads by seed in disturbed rangelands and pastures. Prevent seed production and monitor rosettes. [J-houndstongue](https://www.jeffco.us/2414/Houndstongue)

## People

Species-specific human ingestion effects were not established in the reviewed county source. This is an evidence gap, not proof of safety.

## 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

Contains alkaloids poisonous to livestock. The county explicitly advises against grazing it. [J-houndstongue](https://www.jeffco.us/2414/Houndstongue)

## 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-houndstongue** — [Houndstongue](https://www.jeffco.us/2414/Houndstongue), Jefferson County, Colorado. Accessed 2026-09-07T00:27:22+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=houndstongue) — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.

# Appendix for agents

## 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.
- **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 |
|---|---|---|---|---|
| houndstongue-1 | Recognize | Species-specific | J-houndstongue | No quantitative exposure threshold established here. |
| houndstongue-2 | Plants & habitat | Species-specific | J-houndstongue | No quantitative exposure threshold established here. |
| houndstongue-3 | People | Review limitation | Review limitation | Species-specific human ingestion effects were not established in the reviewed county source. |
| houndstongue-4 | Dogs & cats | Review limitation | Review limitation | Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources. |
| houndstongue-5 | Other animals | Species-specific | J-houndstongue | 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).

## 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/houndstongue/

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

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

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