Plants annual or facultatively perennial. Vegetative stems submersed with elongate internodes, or emersed and procumbent. Flowering stems 1-9 cm, distal internode 0.5-4 cm. Sessile leaves forming basal rosette, blade linear to oblanceolate, thin, 2.4-3.7 cm × 3-8 mm. Petiolate leaves floating or emersed; stipule 1-5 cm; petiole 2-13 cm; blade reniform, 1-4 × 1-5 cm, length equal to or less than width, apex obtuse. Inflorescences spicate, 2-8-flowered, elongating in 1 day, usually shorter than spathes, terminal flower sometimes extending beyond spathe apex; spathes 0.8-5.5 cm, glabrous; peduncle 0.5-4.2 cm, glabrous. Flowers opening ca. 3 hours after sunrise, wilting by early afternoon; perianth white, salverform, tube 5-10 mm, limbs zygomorphic, lobes narrowly elliptic, 3-6.5 mm, distal central lobe with yellow or green region at base, sometimes with distal brown spot; stamens unequal, lateral stamens 0.9-2.2 mm, filaments linear, pubescent with white multicellular hairs toward apex; central stamen 2.2-4.7 mm, filament sparsely pubescent with multicellular hairs; style pubescent with multicellular hairs. Seeds 8-14-winged, 0.5-0.9 × 0.3-0.5 mm. 2n = 48. Flowering Jun--Oct. Roadside ditches, edges of streams and ponds, freshwater tidal mudflats; 0--2600 m; Ala., Conn., Del., Fla., Ga., Ill., Ind., Ky., La., Md., Miss., Mo., N.J., N.Y., N.C., Ohio, Pa., S.C., Tenn., Tex., Va., W.Va.; Mexico; throughout Central America; scattered in South America (Argentina, Brazil, Paraguay); naturalized in Italy.
From Flora of Indiana (1940) by Charles C. Deam
Very local in ponds in the southern counties. I have found it on the muddy shore of Hovey Lake, Posey County and elsewhere in natural and artificial ponds. There is a specimen in the herbarium of DePauw University which was collected by D. T. MacDougal in Putnam County, Sept. 12, 1889.
Aerial lvs with floating or emersed, reniform blade 1-4 נ1-5 cm, as wide as or somewhat wider than long; petioles to 1.3 dm; spathe folded, 1-5 cm, loosely sheathing
below; fls 2-8, all opening the same day, only the terminal one sometimes extending past the tip of the spathe; perianth largely white, densely glandular-pubescent outside, the tube 5-10 mm, the lobes 3-6.5 mm, 5 above and one below, the central upper one with 2 yellow (or green) spots at the base; filaments sparsely pubescent with spreading multicellular white hairs at least toward the tip; style pubescent with multicellular hairs; 2n=48. In shallow water or emersed on mud; Conn. and N.Y. to Mo., s. to trop. Amer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.