Herbs, perennial, to 2 m; rhizomes coarse; stolons absent; corms absent. Leaves emersed; petiole terete, 44--58 cm; blade linear to ovate or elliptic, 20.3--35 ´ 0.7--16 cm. Inflorescences racemes or panicles, of 6--13 whorls, emersed, 16--72 ´ 19--60 cm; peduncles 75--125.5 cm; bracts connate more than or equal to ¼ total length, lanceolate to ovate-lanceolate, 3--32 mm, coarse, papillose or not; fruiting pedicels spreading, cylindric, 0.6--3.8 cm. Flowers to 3.3 cm diam.; sepals recurved to spreading, not enclosing flower or fruiting head; filaments cylindric, longer than anthers, pubescent; pistillate pedicellate, without ring of sterile stamens. Fruiting heads 0.5--1.2 cm diam.; achenes oblanceoloid, abaxially keeled, 1.6--2.5 ´ 0.8--1.1 mm, beaked; faces not tuberculate, wings absent, glands 1; beak lateral, erect, 0.3--0.7 mm.
Erect emersed aquatic; lvs lanceolate or ovate, 12-35 נ1-10 cm, without basal lobes; scape 5-20 dm, with 4-10 whorls of fls, sometimes branching at the lowest
whorl, the upper fls staminate on filiform pedicels 2-3 cm, the lower pistillate on stouter, ascending pedicels 1-1.5 cm; bracts oblong-ovate, obtuse or acute, somewhat boat-shaped, 0.5-1.5 cm, evidently, copiously, and irregularly papillate-roughened or somewhat corrugate-ridged on the back; sep reflexed, oblong-ovate, 3-6 mm, roughened like the bracts; pet 8-15 mm; stamens 12-30, the filaments slender, linear, longer than the anthers, roughened with minute scales; achenes 1.5-2.3 mm; narrowly obovate to often falcate, with marginal wings only, or with 1 or 2 poorly developed facial wings, sometimes with a resin-duct on each face; beak broad-based, obliquely ascending, 0.3-0.7 mm; 2n=22. In shallow water and swamps; near the coast from Del. to Fla., Tex., Mex., W.I., and n. S. Amer. Our plants, as here described, are var. media Micheli. (S. falcata) Typical S. lancifolia is mainly tropical and subtropical.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.