Rataj places it in his Section Macrophylli - Subgenus Echinodorus
E. radicans hort.
Petioles 2 - 3 x longer than the blade, membraneously alate on the base, thin to densely pilose under the blade. Pubescence simple or stellate and absent on young or submerged plants. Blade membraneous, sagittato-cordate or triangularly obovate with long blunt lobes, approximately as wide as the midrib length and widest at the base. Blade (6.5) - 20 - 30 cm long and (7_ - 20 - 30 cm wide with 11 - 13 veins (7 - 15 are possible). No pellucid markings.
Stem upright, about twice as long as the leaves, cylindrical, between the whorls triangular, pubescent under whorls as well as petioles.
Inflorescence rarely racemose, usually paniculate having 6 - 13 whorls containing 6 - 9 flowers each. Bracts lanceolate, densely ribbed. Bracts in the first whorl as long as the pedicels, in the other whorls they are a third shorter. Pedicels 1 - 3.5 cm long, sepals broadly ovate, leather-like, densely ribbed, 5 - 6 mm long, petals white, obovate, 15 - 18 mm long, stamens 20 - 24, filaments longer than the anthers, pistils numerous, style longer than the ovary.
Aggregate fruit globular, echinate, 6 - 8 mm in diameter. Achenes flat, subovately-cuneate, 3 x 1.5 mm with 3 - 5 (usually 3) lateral ribs and 2 - 3 oblong and further 3 - 5 small round glands. Stylar beak usually straight, approximately 0.75 mm.
Grow at tropical temperatures with plenty of light and a rich substrate. It can stand lower temperatures however if acclimatised, though it will stay rather smaller and grow more slowly. Water conditions don't seem to be critical. In the smaller aquarium it will often quickly form emerse leaves, which prefer moist conditions and don't like being dried out by being too near lamps etc. It is easy to grow and makes a very good specimen plant for the larger aquarium
See also: List of plants of Cerrado vegetation of Brazil
Rataj, Karel. 1988. The beautiful Echinodorus macrophyllus. TFH 7/88.