USGS - science for a changing world

Northern Prairie Wildlife Research Center

  Home About NPWRC Our Science Staff Employment Contacts Common Questions About the Site

Aquatic and Wetland Vascular Plants of the Northern Great Plains

15. Polygonaceae, the Smartweed Family

1. Polygonum L. -- Smartweed, knotweed, tear-thumb

6. Polygonum lapathifolium L.-- Pale smartweed


Erect to decumbent, simple to widely branching annual (1)2-10 dm tall. Leaf blades lanceolate or elliptic-lanceolate, 4-17(20) cm long, 0.5-3.5(5) cm wide, glabrous above, glabrous to minutely strigose and often glandular-punctate beneath, occasionally finely white-tomentose beneath, acute or acuminate to the narrow, blunt tip, cuneate at the base, on short petioles to 2 cm long; ocreae 5-20 mm long, entire to lacerate, glabrous, not fringed with bristles. Racemes usually numerous, densely flowered, cylindric, erect or often nodding, 0.8-5 cm long, 0.5-1 cm thick. Flowers greenish-white or white to deep pink; calyx 2.5-3.5 mm long, 4- or 5-lobed to below the middle, the outer 2 sepals strongly 3-nerved, each nerve ending in an anchor-shaped fork; stamens usually 6, included; style branches 2. Achenes brown to dark brown, lenticular, concave on the sides, ca. 2 mm long, including the style beak. Jul--Sep. Marshes, wet meadows, ditches, shores, stream banks and other places where water stands temporarily; very common, often abundant; (Circumboreal, s throughout most of the U.S.).
GIF-Polygonum lapathifolium

Polygonum lapathifolium. The spikelike racemes are usually erect and shorter on smaller plants. The flowers can be strongly pink.
GIF- Distribution Map

Map key


Previous Species -- Polygonum hydropiperoides Michx.-- Mild water pepper
Return to Family -- Polygonaceae - The Smartweed Family
Next Species -- Polygonum pensylvanicum L.-- Pennsylvania smartweed

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/plants/vascplnt/species/polylapa.htm
Page Contact Information: Webmaster
Page Last Modified: Saturday, 02-Feb-2013 06:45:44 EST
Menlo Park, CA [caww55]