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Montana Field Guide

Montana Field Guides

Lady's Thumb Smartweed - Polygonum persicaria
Other Names:  Spotted Lady's-thumb, Persicaria maculosa, Persicaria maculata

Non-native Species

Global Rank: G3G5
State Rank: SNA
C-value: 1

Agency Status


External Links

General Description
Scabrous to sparsely puberulent annual. Stems erect to decumbent, rooting at the nodes, branched, 10–80 cm. Leaves short-petiolate; the blades lanceolate, 3–12 cm long, usually with a dark spot in the center that becomes obscure with drying; stipules brown below, scarious above, 4–10 mm long, papery, ciliate-margined, strigose to glabrous. Flowers 2–3 mm long, in cylindrical, compound racemes 1–3 cm long; pedicels 1–3 mm long, ascending; tepals 4 to 5, green below, white to pink above, 3-veined. Achene 2- to 3-sided, 2–3 mm long, shiny, black (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Species Range
Montana Range Range Descriptions


Range Comments
Cosmopolitan, introduced throughout North America; native to Europe (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 77

(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)

Moist soil of fields, gardens, roadsides, wetlands; plains, valleys (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.
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Citation for data on this website:
Lady's Thumb Smartweed — Polygonum persicaria.  Montana Field Guide.  .  Retrieved on , from