---
{
  "id": "black-henbane",
  "name": "Black henbane",
  "scientific": "Hyoscyamus niger",
  "category": "invasive",
  "status": "Colorado noxious weed · List B — Stop the spread",
  "status_sources": [
    "CO-rules-2025"
  ],
  "warning": "Highly poisonous; keep animals away",
  "warning_tone": "danger",
  "aliases": [],
  "taxonomy_note": "",
  "source_ids": [
    "CO-rules-2025",
    "N-hyoscyamus-niger",
    "S27",
    "Fremont-list-definitions"
  ],
  "description": "Black henbane: Highly poisonous; keep animals away. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "N-hyoscyamus-niger"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "black-henbane-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "N-hyoscyamus-niger"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "black-henbane-2"
    },
    {
      "label": "People",
      "sources": [
        "N-hyoscyamus-niger"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "black-henbane-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [
        "N-hyoscyamus-niger"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "black-henbane-4"
    },
    {
      "label": "Other animals",
      "sources": [
        "N-hyoscyamus-niger"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "black-henbane-5"
    },
    {
      "id": "black-henbane-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": "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/black-henbane.md"
}
---

# Black henbane

*Hyoscyamus niger*

**Colorado noxious weed · List B — Stop the spread.** [CO-rules-2025](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2)

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).

> **Highly poisonous; keep animals away.** [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

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

![Pale yellow henbane flowers with purple veins and dark purple throats above lobed leaves.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-hyoscyamus-niger-01.jpg)

**flowers** — Pale yellow henbane flowers with purple veins and dark purple throats above lobed leaves.

Photo: H. Zell; [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0); [source record](https://commons.wikimedia.org/wiki/File:Hyoscyamus_niger_0002.JPG); [original image](https://upload.wikimedia.org/wikipedia/commons/4/44/Hyoscyamus_niger_0002.JPG). Source-identified photograph with visual consistency check Hyoscyamus niger , Solanaceae, Henbane, Stinking Nightshade, flowers; Botanical Garden KIT, Karlsruhe, Germany. The whole, fresh, blooming plant is used in homeopathy as remedy: Hyoscyamus (Hyos.) Source labeling and visible consistency checked; not an independent specimen determination. Wikimedia-generated thumbnail rescaling only; downloaded bytes unchanged. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Macro view of glandular hairs projecting from a green stem, with a 3 mm scale.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-hyoscyamus-niger-07.jpg)

**stem hairs** — Macro view of glandular hairs projecting from a green stem, with a 3 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:Hyoscyamus_niger_sl42.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/a/a9/Hyoscyamus_niger_sl42.jpg). Source-identified photograph with visual consistency check Stem with glandular hairs Taxonym: Hyoscyamus niger ss Fischer et al. EfÖLS 2008 ISBN 978-3-85474-187-9 Location: S Hollabrunn, district Hollabrunn, Lower Austria - ca. 220 m a.s.l. Habitat: pumpkin field Source labeling and visible consistency checked; not an independent specimen determination. Wikimedia-generated thumbnail rescaling only; downloaded bytes unchanged. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Whole flowering henbane plants with lobed leaves on disturbed gravelly ground.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-hyoscyamus-niger-09.jpg)

**habit** — Whole flowering henbane plants with lobed leaves on disturbed gravelly ground.

Photo: Bjoertvedt; [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0); [source record](https://commons.wikimedia.org/wiki/File:Hyoscyamus_niger_IMG_8882_bulmeurt_hoved%C3%B6ya.JPG); [original image](https://upload.wikimedia.org/wikipedia/commons/a/a9/Hyoscyamus_niger_IMG_8882_bulmeurt_hoved%C3%B6ya.JPG). Source-identified photograph with visual consistency check Photo of Hyoscyamus niger (norwegian: bulmeurt) at the island og Hovedøya, in the inner Oslofjord, Norway. Source labeling and visible consistency checked; not an independent specimen determination. Wikimedia-generated thumbnail rescaling only; downloaded bytes unchanged. Gallery display preserves the full image; the catalog preview uses a CSS crop.


## Recognize

A coarse, hairy annual or biennial with sticky-looking leaves and yellowish flowers marked by purple veins. [N-hyoscyamus-niger](https://plants.ces.ncsu.edu/plants/hyoscyamus-niger/)

## Plants & habitat

Self-seeding produces persistent infestations on disturbed ground. Prevent mature fruits from scattering seed. [N-hyoscyamus-niger](https://plants.ces.ncsu.edu/plants/hyoscyamus-niger/)

## People

Tropane alkaloids can cause severe poisoning, including convulsions and coma. Do not taste or use it as a home remedy. [N-hyoscyamus-niger](https://plants.ces.ncsu.edu/plants/hyoscyamus-niger/)

## Dogs & cats

NC State flags dogs and cats. Treat suspected ingestion as urgent and contact a veterinarian. [N-hyoscyamus-niger](https://plants.ces.ncsu.edu/plants/hyoscyamus-niger/)

## Other animals

The source reports particular seed toxicity to pigs and flags horses. Animal avoidance is not a guarantee against poisoning. [N-hyoscyamus-niger](https://plants.ces.ncsu.edu/plants/hyoscyamus-niger/)

## 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-hyoscyamus-niger** — [hyoscyamus niger — Plant Toolbox](https://plants.ces.ncsu.edu/plants/hyoscyamus-niger/), NC State Extension. Accessed 2026-09-07T01:04:53+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=black-henbane) — 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.


## Identity and evidence boundaries

Match the scientific name and synonyms, not the common name alone.

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 |
|---|---|---|---|---|
| black-henbane-1 | Recognize | Species-specific | N-hyoscyamus-niger | No quantitative safe exposure established here. |
| black-henbane-2 | Plants & habitat | Species-specific | N-hyoscyamus-niger | No quantitative safe exposure established here. |
| black-henbane-3 | People | Species-specific | N-hyoscyamus-niger | No quantitative safe exposure established here. |
| black-henbane-4 | Dogs & cats | Species-specific | N-hyoscyamus-niger | No quantitative safe exposure established here. |
| black-henbane-5 | Other animals | Species-specific | N-hyoscyamus-niger | 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).

## 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/black-henbane/

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

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

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