4. Bistorta officinalis Delarbre, Fl. Auvergne, ed. 2. 2: 516. 1800.
Polygonum bistorta Linnaeus, Sp. Pl. 1: 360. 1753; Bistorta major Gray; Persicaria bistorta (Linnaeus) Sampaio
Plants (20-)30-100(-120) cm; rhizomes contorted. Stems 1(-2). Leaves: ocrea brown, cylindric, 15-50(-70) mm, margins oblique, glabrous; petiole attached proximally to sheath 10-45(-70) mm, prominently winged distally, 100-260 mm, wing 1-6(-12) cm; blade lanceolate to ovate, 6-15(-21) × 2.5-9(-10) cm, base abruptly contracted, truncate to cuneate, often asymmetric, margins entire or obscurely and irregularly repand, usually wavy, apex acute to acuminate, rarely obtuse, abaxial face glabrous or pubescent with whitish or brownish hairs, glaucous, adaxial face glabrous, not glaucous; cauline leaves 3-6, petiolate proximally, sessile distally, gradually reduced distally, blade triangular-lanceolate to linear. Inflorescences 1, short-cylindric to ovoid, 35-65 × 12-20 mm, bulblets absent; peduncle 1-15 cm. Pedicels ascending, 1.5-7 mm. Flowers 1-2 per ocreate fascicle; perianth pink; tepals elliptic to ovate, 3-4 mm, apex obtuse; stamens exserted; anthers pink to purple. Achenes brown, 3.3-4.5 × 2.5-3 mm, shiny, smooth. 2n = 48.
Flowering May-Aug. Fields, meadows; 10-200 m; introduced; Nfld. and Labr. (Nfld.), N.S.; Maine, Mass., Vt.; Europe; Asia.
Chromosome numbers of 2n = 24, 44, 46, 48, and ca. 50 have been reported for Bistorta officinalis (B. Jonsell and T. Karlsson 2000+, vol. 1). A count of 2n = 48 made by Á. Löve and D. Löve (1988) was from a plant from California; it probably was cultivated.