Herbs, perennial, to 45 cm; rhizomes absent; stolons present; corms present. Leaves emersed; petiole triangular, erect to ascending, 6.5--51 cm; blade sagittate, rarely hastate, 1.5--30.5 ´ 2--17 cm, basal lobes equal to or less than remainder of blade. Inflorescences racemes, rarely panicles, of 3--9 whorls, emersed, 4.5--28.5 ´ 4--23 cm; peduncles 10--59 cm; bracts connate more than or equal to ¼ total length, elliptic to lanceolate, 3--8 mm, delicate, not papillose; fruiting pedicels spreading, cylindric, 0.5--3.5 cm. Flowers to 4 cm diam.; sepals recurved to spreading, not enclosing flower or fruiting head; filaments cylindric, longer than anthers, glabrous; pistillate pedicellate, without ring of sterile stamens. Fruiting heads 1--1.7 cm diam; achenes oblanceoloid, without abaxial keel, 2.5--3.5 ´ to 2 mm, beaked; faces not tuberculate, wings absent, glands (0--)1(--2); beak lateral, horizontal, 1--2 mm. 2n = 22. Flowering summer--fall. Wet ditches, pools, and margins of streams and lakes; 0--1500 m; Alta., B.C., Man., N.B., N.S., Ont., P.E.I., Que., Sask.; Ala., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis.; c, s Mexico; Central America (Guatemala); South America (Colombia, Ecuador, Venezuela). Sagittaria latifolia has been divided into numerous species and varieties. It was divided into two varieties, based upon the presence of pubescence over the entire vegetative plant (C. Bogin 1955; K. Rataj 1972). We have examined numerous specimens and found that many from the southeastern United States are pubescent; we believe that this character alone is insufficient for recognition of the varieties.
Vegetatively very plastic, ±erect and with large, edible tubers; lvs sagittate or sometimes narrow and phyllodial, the blade 5-40 נ0.5-25 cm, with narrow or broad lobes; scape 1-12 dm, with 2-15 whorls of fls, sometimes branching at the lowest whorl, the upper fls staminate on short pedicels, the lower pistillate on longer, ±ascending pedicels; bracts 4-15 mm, boat-shaped, broad-based, rounded above or broadly acute, 4-15 mm, papery but friable at the tip; sep ovate, obtuse, 5-11 mm, reflexed in fr; pet 1-2 cm; stamens 20-40, on slender, glabrous filaments; achenes 2.5-4 mm, winged on the margins only, or with a poorly developed wing on each face, with (var. latifolia) or without (var. pubescens) resin-ducts; beak 0.6-1.8 mm, set at essentially right angles to the body; 2n=22. Abundant in swamps, ponds, and streams; N.S. and Que. to s. B.C., s. to trop. Amer. July-Sept. The widespread, glabrous var. latifolia is uncommon in the principal range of the stellate-hairy var. pubescens (Muhl.) J. G. Sm., which occurs chiefly from the mts. to the coast, from s. Pa. to W.Va. and Ga., w. occasionally to O., Tenn., and Tex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.