Aquatic and Wetland Vascular Plants of the Northern Great Plains
15. Polygonaceae, the Smartweed Family
1. Polygonum L. -- Smartweed, knotweed, tear-thumb8. Polygonum persicaria L.-- Lady's thumb
Erect to spreading, simple to branched annual 2-8 dm tall, the stems often reddish. Leaf blades lanceolate to elliptic-lanceolate, 3-15 cm long, 0.5-3 cm wide, glabrous to sparsely strigose, usually puncticulate, especially beneath, acute to long-acuminate, cuneate at the base, subsessile or on petioles to 1 cm long; ocreae 5-15 mm long, fringed with bristles, glabrous to strigose. Racemes usually few to many, globose to cylindric, 0.5-2.5 cm long, 0.5-1 cm thick. Flowers light to deep pink; calyx 2.5-3 mm long, 5-lobed to near the middle; stamens 6, included; style branches 2 or 3. Achenes black, shiny, lenticular or some often trigonous, 2-2.5 mm long. Jul--Sep. Springs, shores, stream banks and ditches, where water is fresh; occasional, most common in the e part; (Intro. from Europe and now throughout N.Amer.).
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