Herbs, annual or perennial, to 75 cm; rhizomes absent; stolons present; corms present. Leaves emersed, sessile, phyllodial, linear to lanceolate, flattened, 15--25(--40) ´ 1.5--4 cm, or petiole triangular, 15--50 cm, blade linear to elliptic-lanceolate, 4--10 ´ 0.3--2 cm. Inflorescences racemes, of 3--6 whorls, 1.5 ´ 4 cm; peduncle 20--60 cm; bracts connate greater than or equal to ¼ total length, ovate, 4--10 mm, nearly scarious, not papillose; fruiting pedicels spreading, cylindric, 0.8--3 cm. Flowers to 0.8 cm diam.; sepals recurved to spreading, not enclosing flower; filaments dilated, exceeding anthers in length, pubescent; pistillate pedicellate, without ring of sterile stamens. Fruiting heads 1.2--2 cm diam.; achenes cuneate-obovoid, abaxially keeled, 2.5--3 ´ 1.4--1.8 mm, beaked; faces not tuberculate, wings 1, ± entire, glands absent; beak ascending to horizontal, 0.4--0.7 mm.

Flowering summer (Jul--Aug). Sandy margins and bottoms of lakes, ponds, and swamps; 100--1000 m; Ont.; Ill., Iowa, Mich., Minn., Mo., Nebr., Wis.