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Montana Field Guide

Montana Field Guides

Dense-flower Knotweed - Polygonum polygaloides ssp. confertiflorum
Other Names:  Polygonum confertiflorum

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Status Under Review
Native Species

Global Rank: G4G5T3T4
State Rank: S2S3
(see State Rank Reason below)

Agency Status


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State Rank Reason (see State Rank above)
Ten collections exist at MONTU from five different counties. Typical habitat includes the margins of vernal pools and ponds but is also known from roadcuts and other seasonally moist habitats. Dense-flower knotweed has been found from valley bottoms to moderate elevations in the mountains. Though it has been considered rare in the state and range-wide, it appears likely that it will be found to be more common than previosuly thought.
General Description
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Range Comments
Hickman (1993) lists: northern California to Washington, Wyoming and Montana. Several other sources corroborate Hickman under the synonym Polygonum confertiflorum: Peck (1961) lists Willamette Valley and east of Cascades in Oregon. Kartesz (1988) cites only Elko County, Nevada. Lackschewitz (1991) notes one report from southwest Ravalli County, Montana. Davis (1952) confirms P. confertiflorum in Idaho. And Scoggan lists a range of southwest Saskatchewan south to northern California and northern Wyoming. Kartesz (unpublished data 1995) also includes Alberta, British Columbia, Arizona and New Mexico for P. polygaloides ssp. confertiflorum.

Grows in vernally flooded places that are desiccated in summer. Such habitats are very rare in Montana due to the continental climate and the porous substrates in valley floors.

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.
    • 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. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • 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:
Dense-flower Knotweed — Polygonum polygaloides ssp. confertiflorum.  Montana Field Guide.  .  Retrieved on , from