Bistorta (Linnaeus) Scopoli, Meth. Pl. . 24. 1754.
Bistort [Latin, bi-, twice, and tortus, twisted, alluding to the rhizomes of some species]
Craig C. Freeman, Harold R. Hinds†
Credit: Harvard University Herbaria
Polygonum [unranked] Bistorta Linnaeus, Sp. Pl. 1: 360. 1753
Herbs, perennial; roots fibrous, rhizomatous. Stems erect, simple, glabrous. Leaves mostly basal, some cauline, alternate, petiolate or sessile; ocrea persistent or disintegrating with age and deciduous entirely or distally, chartaceous; blade linear or lanceolate to elliptic, oblong-ovate, or ovate, margins entire or obscurely and irregularly repand. Inflorescences terminal, spikelike. Pedicels present. Flowers bisexual, 1-2 per ocreate fascicle, base not stipelike; perianth nonaccrescent, white, greenish white, pink, or purplish pink, rarely red, campanulate, glabrous; tepals 5, connate proximally ca. 1/ 5 their length, petaloid, monomorphic or slightly dimorphic, outer larger than inner; stamens 5-8, sometimes poorly developed; filaments distinct or connate basally, outer ones sometimes adnate to perianth tube, glabrous; anthers yellow, pink, red, purple, or blackish, ovate to elliptic; styles 3, erect or spreading, distinct or connate proximally; stigmas 2-3, capitate. Achenes included or exserted, brown to dark brown, unwinged, 3-gonous, glabrous. Seeds: embryo curved. x = 11, 12.
Species ca. 50 (4 in the flora): arctic and temperate North America, Europe, Asia.
Bistorta often is included in Polygonum in the broad sense or in Persicaria. It is accepted here as a distinct genus based on habit, morphology, and anatomy (K. Haraldson 1978; L.-P. Ronse Decraene and J. R. Akeroyd 1988). In the species of the flora area, the base of the petiole forms a long, tubular sheath distal to the node from which the leaf arises and proximal to the point of divergence of the petiole. Distal to the sheath is the ocrea, which usually is darker and thinner.