Bohemian knotweed
Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.
Reynoutria × bohemica
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.
Hybrid regrows from small fragments. Exposure help.
Identification caveat: This is the Japanese × giant knotweed hybrid. Intermediate-looking leaves alone cannot establish a hybrid identification.
Still researching this plant
This is a sourced working profile. Evidence is incomplete for People, 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.
Patrick Hacker · CC BY 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. This is the source-identified hybrid, not a substituted parent species. The selected observation is research grade; these views show young foliage and leaf hairs, and are not a genetic or specimen-based confirmation of hybridity.
iNaturalist large server-resized image; no local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Patrick Hacker · CC BY 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. This is the source-identified hybrid, not a substituted parent species. The selected observation is research grade; these views show young foliage and leaf hairs, and are not a genetic or specimen-based confirmation of hybridity.
iNaturalist large server-resized image; no local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Patrick Hacker · CC BY 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. This is the source-identified hybrid, not a substituted parent species. The selected observation is research grade; these views show young foliage and leaf hairs, and are not a genetic or specimen-based confirmation of hybridity.
iNaturalist large server-resized image; no local crop, colour change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Recognize
A spreading perennial with hollow stems and leaves intermediate between Japanese and giant knotweed. Leaf-base shape and underside hairs help identification. WA-bohemian-knotweed
Plants & habitat
Rhizomes, stem fragments and seed spread persistent colonies that exclude other streambank plants. WA-bohemian-knotweed
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.
- WA-bohemian-knotweed — Bohemian Knotweed, Washington State Noxious Weed Control Board. Accessed 2026-09-07T01:09:00+00:00. Locator: Identification, ecological impacts, management; Washington legal class not applied to Colorado.
- 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.