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Montana Field Guide

Montana Field Guides

Japanese Knotweed - Polygonum cuspidatum
Other Names:  Fallopia japonica

Noxious Weed: Priority 1B

Global Rank: GNR
State Rank: SNA
* (see State Rank Reason below)

Agency Status
USFWS:
USFS:
BLM:
MNPS Threat Rank:
C-value: 0

External Links






State Rank Reason (see State Rank above)
Part of the Japanese Knotweed Complex
  • Details on Status Ranking and Review
    Japanese Knotweed (Polygonum cuspidatum) Conservation Status Review
    Review Date =
 
General Description
Dioecious, rhizomatous perennial. Stems erect, branched, 1–2 m. Leaves petiolate; the blades ovate, 8–20 cm long with pointed tips and a truncate base; stipules brown, glabrous, 4–6 mm long. Flowers apparently perfect but functionally unisexual, 5–7 mm long with a tubular base, numerous in stipulate, axillary panicles; pedicels spreading, 3–5 mm long; tepals white to pink. Achene shiny-brown, 2–4 mm long, 3-sided, enclosed by an inflated perianth (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Range Comments
BC to QC south to most of the US; introduced from Asia as a garden ornamental (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 15

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat

Management

References
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Citation for data on this website:
Japanese Knotweed — Polygonum cuspidatum.  Montana Field Guide.  .  Retrieved on , from