Lythrum anceps (Koehne) Makino; L. argyi H. Léveillé; L. intermedium Ledebour ex Colla; L. salicaria var. anceps Koehne; L. salicaria var. glabrum Ledebour; L. salicaria var. intermedium (Ledebour ex Colla) Koehne; L. salicaria var. mairei H. Léveillé.

Perennial herbs or subshrubs, 0.3-1.5 m tall, scabrous or sparsely to densely gray pubescent [or tomentose], sometimes somewhat glabrescent. Stem erect, 4-angled. Leaves opposite or 3-whorled, sometimes alternate toward stem apex, ovate-lanceolate to broadly lanceolate, 2.5-10 × 0.5-1.5 cm, base rounded, truncate, or semiclasping, apex acute to subobtuse. Inflorescences terminal, spicate, 15-35 cm; bracts broadly lanceolate or deltoid-ovate. Flowers in 1- to multi-flowered whorled axillary cymes, shortly pedicellate. Floral tube 5-8 × 1.5-2 mm, 12-ribbed; sepals deltate, 0.5-1 mm; epicalyx segments erect, linear, 1.5-2 mm, much longer than sepals. Petals reddish purple to rose-purple, lanceolate-oblanceolate, 7-10 × 1.5-3 mm. Fl. Jul-Sep, fr. Oct. 2n = 30, 50, 58, 60.

Great variability, especially in degree of indumentum and leaf shape, has led to recognition of many microspecies and infraspecific taxa that are not satisfactorily separated when the species is investigated over its geographic range. Apparent hybridization between Lythrum salicaria and L. virgatum and among the many races of L. salicaria in E Europe and Asia have further confused the taxonomy. Lythrum salicaria is recognized here as a single species with localized variants. Formal names are not recognized for variants within the species until a biosystematic study of the species complex can be made.

Damp grasslands, banks. Almost throughout China [widespread in northern latitudes worldwide, Afghanistan, India, Japan, Korea, Mongolia, E Russia; N Africa, Europe, North America].