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Montana Field Guide

Montana Field Guides

Johnston's Knotweed - Polygonum sawatchense
Other Names:  Polygonum douglasii ssp. johnstonii

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Status Under Review
Native Species

Global Rank: GNR
State Rank: SNR

Agency Status


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General Description
Annual. Stems erect, simple or branched at the base, 5–35 cm. Leaves short-petiolate; blades 8–20 mm long, linear-oblong, reduced above; stipules lacerate, 2–10 mm long. Flowers 3–4 mm long, 1 to 4 in leaf axils; pedicels erect, 1–4 mm long; tepals green with white to pink margins. Achene 3-sided, 2–3 mm long, shiny black (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Range Comments
BC to SK south to CA, AZ and NM. One collection from an alpine, stony, calcareous slope in Beaverhead County (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).


The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus bifarius, Bombus flavifrons, Bombus frigidus, Bombus melanopygus, Bombus sylvicola, Bombus occidentalis, Bombus pensylvanicus, Bombus insularis, and Bombus kirbiellus (Macior 1974, Colla and Dumesh 2010).

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Macior, L.M. 1974. Pollination ecology of the Front Range of the Colorado Rocky Mountains. Melanderia 15: 1-59.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
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Citation for data on this website:
Johnston's Knotweed — Polygonum sawatchense.  Montana Field Guide.  .  Retrieved on , from