Northern Prairie Wildlife Research Center
Aquatic and Wetland Vascular Plants of the Northern Great Plains
15. Polygonaceae, the Smartweed Family
1. Polygonum L. -- Smartweed, knotweed, tear-thumb
11. Polygonum sagittatum L.-- Tear-thumb, arrow-vine
Slender annual; stems weak, usually reclining on surrounding vegetation,
to 2 m long, strongly 4-angled, armed with reflexed prickles on the angles,
the prickles usually continuous onto the petioles, leaf midribs and peduncles.
Leaves mostly long-petioled below, becoming short-petioled upward on
the stem, the blades lanceolate to elliptic and sagittate, 3-10 cm long, 0.8-2.5
cm wide, acute, the basal lobes straight or incurved; ocreae 5-10 mm
long, sparsely ciliate. Racemes terminal and axillary on slender peduncles,
globose, 5-10 mm long. Flowers whitish or pinkish; calyx 2.5-3
mm long, 5-parted to below the middle; stamens 8, included; style
branches 3. Achenes brown to black, shiny, trigonous, 2-3 mm long.
Jul--Sep. Swamps, springs and wet meadows; rare in ND and SD, frequent in NE
Sand Hills; (Newf. and Que. to Sask., s to FL and TX).
Previous Species -- Polygonum ramosissimum
Michx.-- Bushy knotweed
Return to Family -- Polygonaceae -
The Smartweed Family
Next Species -- Rumex altissimus Wood -- Pale