Lythrum salicaria L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Stout, erect perennial herb 5–15 dm, glabrous or more often pubescent or, especially upwards, even subtomentose; lvs opposite or ternate, sessile, lanceolate to nearly linear, 3–10 cm, the larger ones cordulate at base; spikes 1–4 dm, interspersed with foliaceous, lanceolate to ovate bracts; fls trimorphic as to the style and stamens; appendages of the hypanthium linear, fully twice as long as the sep; pet red-purple, 7–12 mm; stamens mostly 12, alternately longer and shorter; disk wanting; 2n=30, 50, 60. Native of Eurasia; in wet places from Nf. and Que. to N.D., s. to Va., Mo., and Kans., and occasionally w. to the Pacific. July–Sept.