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Large Knotweed -
Polygonum douglasii ssp. majus
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Annual. Stems erect, angled, branched near the base, 8–60 cm. Leaves linear-lanceolate, 2–5 cm long; stipules glabrous, 6–10 mm long. Flowers 4–5 mm long, 2 to 4 in upper leaf axils; pedicels reflexed, ca. 1 mm long; tepals white to rose. Achene 3-sided, 3–5 mm long, black (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX
BC to CA, UT and CO (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap:
(Macior 1974, Colla and Dumesh 2010).
Literature Cited Above
Legend: 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. Web Search Engines for Articles on "Large Knotweed"