Hairy willow-herb
Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.
Epilobium hirsutum
Colorado noxious weed · List A — Eradicate. CO-rules-2025
Uncommon in Colorado. All populations are designated for eradication statewide. This is a management category, separate from danger ratings. Category source · What the lists mean.
Spreads through wetland vegetation. Exposure help.
Still researching this plant
This is a sourced working profile. Evidence is incomplete for People, Dogs & cats, Other animals. 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.
Mathias keraudren · CC0
Photo source and identification
Original record · Original image
Source 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 local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Salicyna · CC BY-SA 4.0
Photo source and identification
Original record · Original image
Source 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 local crop, colour 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 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 local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Recognize
Hairy stems and toothed leaves bear pink, four-petaled flowers with notched tips. Long capsules release hairy seeds. N-epilobium-hirsutum
Plants & habitat
Rhizomes and wind-carried seeds spread this wet-site plant. Inspect nursery stock and prevent seed dispersal. N-epilobium-hirsutum
People
The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for people. Missing evidence does not establish safety.
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
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
This is a statewide eradication priority. Contact your county weed program promptly for identification and an approved management and disposal plan. CO-rules-2025
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-epilobium-hirsutum — epilobium hirsutum — Plant Toolbox, NC State Extension. Accessed 2026-09-07T01:04:51+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.