Herbs, perennial, to 130 cm; rhizomes absent; stolons present; corms present. Leaves emersed; petiole 5-winged, 19--85 cm; blade sagittate, 3--19 ´ 2.5--11 cm, basal lobes ± equal to remainder of blade. Inflorescences racemes, of 5--12 whorls, emersed, 10--29 ´ 3--5 cm; peduncles 25--105 cm; bracts distinct or if connate, then less than ¼ total length, lanceolate, 7--30 mm, papery, not papillose; fruiting pedicels spreading to ascending, cylindric, 0.3--2.3 cm. Flowers to 3 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--2.2 cm diam.; achenes obovoid, without abaxial keel, 2.1--3.2 ´ 1.4--2.3 mm, beaked; faces not tuberculate, wings 0--2, ± entire, glands absent; beak lateral, strongly recurved, 4--17 mm. 2n = 22. Flowering summer--early fall (Jul--Oct). Slightly basic to slightly acidic ponds, lakes, and swamps; 1--300 m; Ala., Ark., Fla., Ga., Ill., Ind., Iowa, Ky., La., Md., Miss., Mo., N.J., N.Y., N.C., Ohio, Pa., S.C., Tenn., Va., W.Va. The name Sagittaria longirostra (Micheli) J. G. Smith has been misapplied to S. australis (J. G. Smith) Small (E. O. Beal et al. 1980).
Main portion of the lf-blade deltoid- ovate, relatively blunt, 3-13 נ2.5-10 cm, 0.7-2.2 times as long as wide, the basal lobes broad; petiole sharply 5-winged in section; fls in 5-12 whorls; bracts 7-30 mm, equaling or longer than the 7-23 mm pedicels, stramineous, papery-firm, broad-based and long-acuminate; receptacle not markedly echinate; achenes 2.3-3.2 mm, without resin-ducts, usually with 1 wing on each face, these not extending into the beak; beak mostly 0.7-1.7 mm, often ±incurved above the obliquely ascending base; 2n=22; otherwise much like no. 4 [Sagittaria engelmanniana J. G. Sm]. Mostly in circumneutral water of lakes, ponds, or swamps; N.Y., Pa., and N.J. to S.C. and Ga., w. to c. O., s. Ind., se. Mo., and Miss., mainly inland. July-Sept. (S. longirostra, misapplied)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.