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Is Japanese knotweed illegal in Idaho?
Sources (3)
Also called: Reynoutria (Fallopia) japonica. Last checked against official sources: 2026-10-14.
Federal noxious weed list (7 CFR 360.200): Japanese knotweed is not listed.
What Idaho's official list says
| List / legal category | Listed as | List note | What it means |
|---|---|---|---|
| Statewide Control list — Idaho noxious weed (IDAPA 02.06.09.220) — articles carrying its seeds or parts, including nursery stock, may not be sold (§ 02.06.09.230) | Polygonum cuspidatum | Japanese knotweed | Yes — listed as prohibited |
Effective dates
- The official list entry does not state a separate effective date for this species. See the linked law for when the listing took effect.
Already have it in your yard?
Most state invasive-plant laws, including the list wording above, target selling, distributing, propagating or planting. They generally do not order you to remove a plant already in your yard, but some noxious-weed laws do require control. Read the linked law or ask your county Extension office.
Native alternatives for Idaho
- Red osier dogwood (Cornus sericea)
Each is recorded as native to Idaho in the USDA NRCS PLANTS Database state distribution (retrieved 2026-10-14). Check size, sun and soil fit for your site with your local Extension office.
Japanese knotweed in other states
Alabama California Colorado Connecticut Delaware Illinois Indiana Kentucky Maine Massachusetts Michigan Minnesota Montana Nebraska New Hampshire New York Ohio Oregon Pennsylvania Utah Vermont Virginia Washington West Virginia Wisconsin
See every plant on Idaho's invasive & noxious plant lists, or check any plant.
Not legal advice. PlantLegit summarizes official lists and links the source. Laws change, local (county/city) rules may add restrictions, and the official text controls. "What it means" is our plain-English label; read the exact list wording. Confirm with the agency before buying, selling or removing plants. Full disclaimer.