Herbs, perennial, stout, to 200 cm; rhizomes present. Leaves emersed; petiole 4--5-ridged, to 115 cm; blade with translucent markings dots and short distinct lines, absent in smaller leaves, elliptic to broadly ovate, 16--28 ´ 8--23 cm, base attentuate to cordate. Inflorescences panicles, of 4--9 whorls, each 9--16-flowered, erect, to 65 ´ 45 cm, not proliferating; peduncles ridged, to 131 cm; rachis 3--4-ridged; bracts distinct, lanceolate, 4--7 mm, coarse, margins coarse; pedicels spreading, 1.5--7.5 cm. Flowers 4 cm wide; sepals erect, 21-veined, veins not papillate; petals not clawed; stamens 21; anthers versatile; pistils ca. 200. Fruits oblanceolate, terete, 5-ribbed, not abaxially keeled, 2.5 ´ 0.6--1 mm; glands 4--5; beak terminal, 0.5 mm. Chromosome number unknown.

Flowering summer--fall. Sandy soil at edge of broadleaf evergreen forest; of conservation concern; 0--10 m; Fla.

Echinodorus floridanus is a recently discovered taxon, known only from the type locality, which is within metropolitan Pensacola, Florida. The plants form a large colony that is bisected by a state highway. This species is by far the largest species of the genus in North America.