---
{
  "id": "johnsongrass",
  "name": "Johnsongrass",
  "scientific": "Sorghum halepense",
  "category": "invasive",
  "status": "Colorado noxious weed · List C — Manage widespread weeds",
  "status_sources": [
    "CO-rules-2025"
  ],
  "warning": "Livestock cyanide risk; added fire fuel",
  "warning_tone": "danger",
  "aliases": [],
  "taxonomy_note": "",
  "source_ids": [
    "CO-rules-2025",
    "N-sorghum-halepense",
    "S27",
    "Fremont-list-definitions"
  ],
  "description": "Johnsongrass: Livestock cyanide risk; added fire fuel. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "N-sorghum-halepense"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "johnsongrass-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "N-sorghum-halepense"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "johnsongrass-2"
    },
    {
      "label": "People",
      "sources": [
        "N-sorghum-halepense"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "johnsongrass-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "johnsongrass-4"
    },
    {
      "label": "Other animals",
      "sources": [
        "N-sorghum-halepense"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "johnsongrass-5"
    },
    {
      "id": "johnsongrass-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": "C",
  "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": [
          "johnsongrass-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": "C — Manage widespread weeds",
  "source": "content/plants/johnsongrass.md"
}
---

# Johnsongrass

*Sorghum halepense*

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

Widespread and well established. Control is recommended by the state; local governments may require management. 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).

> **Livestock cyanide risk; added fire fuel.** [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**. 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.

![Sorghum halepense: Close view of grass spikelets with dangling reddish anthers.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-sorghum-halepense-07-02-flower.jpg)

**flower** — Close view of grass spikelets with dangling reddish anthers.

Photo: Jim Conrad; [Public domain](https://commons.wikimedia.org/wiki/File:Sorghum_halepense-flowers.jpg#Licensing); [source record](https://commons.wikimedia.org/wiki/File:Sorghum_halepense-flowers.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/f/f5/Sorghum_halepense-flowers.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.

![Sorghum halepense: Long flat green leaf blades with conspicuous pale midribs.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-sorghum-halepense-07-06-leaf.jpg)

**leaf** — Long flat green leaf blades with conspicuous pale midribs.

Photo: Rsberzerker; [Public domain](https://commons.wikimedia.org/wiki/File:Johnsongrass.JPG#Licensing); [source record](https://commons.wikimedia.org/wiki/File:Johnsongrass.JPG); [original image](https://upload.wikimedia.org/wikipedia/commons/2/28/Johnsongrass.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.

![Sorghum halepense: Tall leafy grass clump with open branching panicles above long arching leaves.](https://denson.github.io/colorado-weed-field-guide/assets/photos/common-priority-photos-sorghum-halepense-07-07-habit.jpg)

**habit** — Tall leafy grass clump with open branching panicles above long arching leaves.

Photo: Stefan.lefnaer; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Sorghum_halepense_sl1.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/2/23/Sorghum_halepense_sl1.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

A tall perennial grass with broad blades, pale midribs and a large, open seedhead. [N-sorghum-halepense](https://plants.ces.ncsu.edu/plants/sorghum-halepense/)

## Plants & habitat

Rhizomes and seed form dense colonies. Productive stands can add fine fuels and promote fire spread. [N-sorghum-halepense](https://plants.ces.ncsu.edu/plants/sorghum-halepense/)

## People

Pollen can trigger hay fever. This is not a substitute for grain sorghum. [N-sorghum-halepense](https://plants.ces.ncsu.edu/plants/sorghum-halepense/)

## 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

Young growth and foliage stressed by frost or hot, dry weather can contain harmful cyanide levels for cattle and horses. Obtain livestock and forage-testing advice before use. [N-sorghum-halepense](https://plants.ces.ncsu.edu/plants/sorghum-halepense/)

## 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-sorghum-halepense** — [sorghum halepense — Plant Toolbox](https://plants.ces.ncsu.edu/plants/sorghum-halepense/), NC State Extension. Accessed 2026-09-07T01:04:55+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=johnsongrass) — 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.
- **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 |
|---|---|---|---|---|
| johnsongrass-1 | Recognize | Species-specific | N-sorghum-halepense | No quantitative safe exposure established here. |
| johnsongrass-2 | Plants & habitat | Species-specific | N-sorghum-halepense | No quantitative safe exposure established here. |
| johnsongrass-3 | People | Species-specific | N-sorghum-halepense | No quantitative safe exposure established here. |
| johnsongrass-4 | Dogs & cats | Review limitation | Review limitation | No quantitative safe exposure established here. |
| johnsongrass-5 | Other animals | Species-specific | N-sorghum-halepense | 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 “C — Manage widespread weeds” 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/johnsongrass/

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

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

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