Acid-water arrowhead

Herbs, perennial, to 70 cm; rhizomes absent; stolons present; corms present. Leaves emersed; petiole triangular, 10--40 cm; blade sagittate, 4.5--10 ´ 0.2--2 cm, basal lobes ± equal to remainder of blade. Inflorescences racemes, of 2--4 whorls, emersed, 5--14 X 2--4 cm; peduncles 20--38 cm; bracts distinct or if connate, then less than ¼ total length, lanceolate, 5--25 mm, not papillose; fruiting pedicels spreading, cylindric, 1.5--3.5 cm. Flowers to 30 mm diam.; sepals recurved to spreading, not enclosing flower or fruiting head; filaments linear, longer than to equal length of anther, glabrous; pistillate pedicellate, without ring of sterile stamens. Fruiting heads 1--1.8 cm diam.; achenes cuneate to obovoid, without abaxial keel, 2.4--4 ´ 1.5--3.8 mm, beaked; faces not tuberculate, wings 1--3, ± entire, glands 1--2; beak lateral, obliquely ascending, (0.7--)1--2.1 mm. 2n = 22.

Flowering late spring--summer (Jun--Sep). Acid waters of ponds, lakes, bogs, and streams; 0--1100 m; Ont.; Ala., Conn., Del., Fla., Ga., Md., Mass., Miss., N.J., N.Y., N.C., Pa., R.I., S.C., Va.