[Polygonum confertiflorum Nutt. ex Piper, morePolygonum imbricatum Nutt. ex S. Wats., Polygonum kelloggii var. confertiflorum (Nutt. ex Piper) R.D. Dorn, Polygonum punctatum var. confertiflorum (Meisn. ex DC.) Fassett, Polygonum watsonii Small]
Stems 2-15 cm. Inflorescences mostly confined to tips of branches, rarely interrupted and continuous from bases of branches or stems, ovoid to cylindric, 7-40 × 5-10 mm; bracts ascending to appressed, linear to linear-lanceolate, 4-11 mm, moderately rigid to rigid, margins revolute, white, scarious portion 0.25-0.4 mm wide; midvein moderately to heavily thickened, lateral veins inconspicuous. Flowers: perianth 1.8-2.2(-2.4) mm; tube 22-30% of perianth length; tepals white or red; perianth tube and base of tepals smooth or, sometimes, papillose; stamens 3. Achenes brown to dark brown, ovate-lanceolate to ovate, 1.5-2 mm, reticulate with longitudinal ridges, dull. Flowering May-Aug. Vernal pools, wet meadows; 500-1900 m; Alta., B.C., Sask.; Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., Utah, Wash., Wyo.