Johnsongrass
Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.
Sorghum halepense
Colorado noxious weed · List C — Manage widespread weeds. CO-rules-2025
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 · What the lists mean.
Livestock cyanide risk; added fire fuel. Exposure help.
Still researching this plant
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.
Jim Conrad · Public domain
Photo source and identification
Original record · Original image
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.
Rsberzerker · Public domain
Photo source and identification
Original record · Original image
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.
Stefan.lefnaer · CC BY-SA 4.0
Photo source and identification
Original record · Original image
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
Plants & habitat
Rhizomes and seed form dense colonies. Productive stands can add fine fuels and promote fire spread. N-sorghum-halepense
People
Pollen can trigger hay fever. This is not a substitute for grain sorghum. N-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
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
References
- CO-rules-2025 — Colorado Noxious Weed Act rules, 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, NC State Extension. Accessed 2026-09-07T01:04:55+00:00. Locator: Description; Attributes; Problems; Poisonous to Humans.
- S27 — 2103 – Colorado Noxious Weeds, PlantTalk Colorado · CSU Extension. Accessed 2026-09-07T00:23:57+00:00. Locator: List A, B and C management categories.