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Aquatic and Wetland Vascular Plants of the Northern Great Plains

15. Polygonaceae, the Smartweed Family

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

4. Polygonum hydropiper L.-- Water pepper

Erect to decumbent, simple to freely branched annual 2-8 m tall; stems often reddish, sometimes rooting at the lower nodes, foliage and flowers peppery to the taste. Leaf blades lanceolate, 3-8 cm long, 0.5-2 cm wide, glabrous except for the strigulose margins, narrowed to a blunt or rounded tip, cuneate at the base, subsessile or short-petioled; ocreae membranous, 5-15 mm long, fringed with bristles, those on the upper half of the stem gibbous, concealing cleistogamous flowers which are like those in the racemes. Racemes often many, loosely flowered, elongate, interrupted in the lower portion, 2-9 cm long. Flowers greenish-white to greenish-pink; calyx 2.5-4 mm long, strongly glandular-punctate, usually 4-parted to slightly below the middle; stamens usually 4 or 6, included by the calyx; style branches 2 or 3. Achenes brown to dark brown, dull, lenticular or trigonous, 2-3 mm long. Late Jul--Sep. Shores and stream banks; frequent in the e part, occasional w; (Intro. from Europe, now ranging from Que. to B.C., s to FL, TX and CA).
GIF- Distribution Map

Map key

Previous Species -- Polygonum coccineum Muhl. ex Willd.-- Marsh smartweed
Return to Family -- Polygonaceae - The Smartweed Family
Next Species -- Polygonum hydropiperoides Michx.-- Mild water pepper

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