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Montana Field Guide

Montana Field Guides

Bohemian Knotweed - Polygonum x bohemicum
Other Names:  Fallopia x bohemica, Polygonum cuspidatum × Polygonum sachalinense

Noxious Weed: Priority 1B
Non-native Species

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

Agency Status
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
    Bohemian Knotweed (Polygonum x bohemicum) Conservation Status Review
    Review Date =
General Description
Glabrous to pubescent and often rhizomatous annual or perennial herb. Stems scandent to erect or less frequently prostrate. Ochrea chartaceous, sometimes deciduous. Petiole base articulated, extrafloral nectaries sometimes present. Leaves broadly ovate to triangular, margins entire or wavy. Inflorescences terminal and lateral, racemose to paniculate. Flowers bisexual, some plants bisexual or others only pistallate, 1-5 per ochreate fascicle. Tepals 5, petaloid, connate basally to nearly completely, dimorphic, the outer 3 winged or keeled and larger than inner 2. Stamens 6-8, anthers yellow to pink or red, ovate to elliptic. Styles 3, spreading, more or less connate below. Stigmas capitate, fimbriate or peltate. Achenes brown to dark brown or black, trigonous but not winged, glabrous (adapted from: Freeman & Hinds, 2005, in Flora N. America, Vol. 5).

Range Comments
Sporadically across North America; most widespread in WA and ID where it is a noxious weed. The MT report is from Mineral County (Kartesz in prep. 2012).

Observations in Montana Natural Heritage Program Database
Number of Observations: 10

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



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

Disturbed places; in North America apparently reproducing mostly vegetatively by rhizomes (adapted from: Freeman & Hinds, 2005, in Flora N. America).


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Citation for data on this website:
Bohemian Knotweed — Polygonum x bohemicum.  Montana Field Guide.  .  Retrieved on , from