Herbs, perennial, to 40 cm, on tidal muds; rhizomes absent; stolons present; corms present. Leaves submersed, phyllodial, lenticular, 5--40 ´ 0.1--0.4 cm, or rarely floating; petiole terete, 2.4--4 cm; blade linear-lanceolate to ovate, 1--2.5 ´ 0.3--1.5 cm. Inflorescences racemes, of 2--7 whorls, floating, 2--11 ´ 1.5--4.5 cm; peduncles 5--40 cm; bracts connate more than ¼ total length, subulate, 1.5--4.2 mm, delicate, not papillose; fruiting pedicels recurved, cylindric to club-shaped, 0.2--1.1 cm. Flowers 0.4--1.2 cm diam.; sepals spreading to recurved in staminate, erect in pistillate, enclosing flower or fruiting head; filaments dilated, longer than anther, glabrous; pistillate pedicellate, occasionally with ring of sterile stamens. Fruiting heads 0.55--0.8 cm diam.; achenes oblanceoloid, abaxially keeled, 2 ´ 1.5 mm, beaked; faces not tuberculate, wings 1--2, crenate, glands 0--1; beak lateral, erect, 0.2--0.4 mm. 2n = 22. Flowering summer--fall. Streams and brackish bays; 0--100 m; Ala., Conn., Del., D.C., Fla., Ga., Md., Mass., Miss., N.J., N.Y., N.C., Pa., R.I., S.C., Va.; South America (Colombia). Sagittaria subulata occurs in shallow brackish waters near the coast. The plants are especially common in areas that are exposed during low tides.
Plants of tidal waters, or submersed in inland waters mainly near the coast; lvs typically phyllodial and bladeless, 5-30 cm נ1-6 mm, or the floating end not infrequently dilated into an ovate or elliptic (rarely cordate or sagittate) blade 2-6 נ1-2 cm; scape erect or floating, to 40(-90) cm; fls in 1-10 whorls (or solitary and terminal), the upper generally staminate and slender-pedicellate, the lower pistillate, on stout, recurved pedicels; bracts thin, mostly connate at base, the lance-ovate body 2-4 mm, with a caudate tip, soon evanescent; sep 2-5 mm, widely spreading in fr; pet 5-10 mm; stamens 7-15, the glabrous or subglabrous filaments subulate, equaling or somewhat longer than the anthers; achenes 1.5-2.5 mm, crenulate-winged on the margins and with 1-3 crenulate wings on each face, the beak subulate, oblique, 0.2-0.5 mm; 2n=22, 44. Coastal states from Mass. and N.Y. (to the upper limits of tidal effect on the Hudson R.) to Fla. and Ala. July-Sept. (S. natans; S. subulata var. gracillima = S. lorata = S. stagnorum, a sporadic deep-water riverine non-tidal form with phyllodial lvs 30-90 cm, the floating ends rarely expanded)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.