Plumeless thistle
Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.
Carduus acanthoides
Colorado noxious weed · List B — Stop the spread. CO-rules-2025
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 · What the lists mean.
Sharp spines; pasture competition. Exposure help.
Identification caveat: Distinguish introduced Carduus from Colorado’s native thistles before removal.
Still researching this plant
This is a sourced working profile. Evidence is incomplete for 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.
Dmitry Makeev · CC BY-SA 4.0
Photo source and identification
Original record · Original image
Source-identified photograph with visual consistency check Carduus acanthoides. Leaf adaxial side. Herbarium of the city Elektrostal Moscow Oblast, 2020 year. Created by scanography. Collection D.Makeev. Scale 1 unit = 1 mm. These are original colors. Please do not make edit. 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.
Robert Flogaus-Faust · CC BY 4.0
Photo source and identification
Original record · Original image
Source-identified photograph with visual consistency check Spiny plumeless thistle ( Carduus acanthoides ), near Groß-Gerau-Wallerstädten at the bike path along L3094, Germany 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.
Robert Flogaus-Faust · CC BY 4.0
Photo source and identification
Original record · Original image
Source-identified photograph with visual consistency check Spiny plumeless thistle ( Carduus acanthoides ) at the bike path between Egelsbach and Erzhausen , Germany 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 spiny thistle with winged stems and relatively small, reddish-purple flowerheads. J-plumeless-thistle
Plants & habitat
Spreads by seed through disturbed pasture and roadsides. Follow-up is needed as rosettes germinate. J-plumeless-thistle
People
Spines on leaves, stems and flowerhead bracts can puncture skin; use protective handling. J-plumeless-thistle
Evidence scope: Physical-risk inference.
Dogs & cats
Spines may injure mouths or paws. Pet-specific chemical toxicity is not established here. J-plumeless-thistle
Evidence scope: Physical-risk inference; ingestion evidence gap.
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.
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.
- J-plumeless-thistle — Plumeless Thistle, Jefferson County, Colorado. Accessed 2026-09-07T00:27:24+00:00. Locator: Description, impacts, Colorado list designation, management.
- 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.