Echinodorus (Burhead) is a genus of plants in the family Alismataceae and distributed in the Western Hemisphere. Its scientific name is derived from Ancient Greek echius – rough husk, and doros – leathern bottle, alluding to ovaries, which in some species are armed with persistent styles, forming prickly head of fruit.
Plants annual or perennial, emersed, floating-leaved, or rarely submersed, glabrous to stellate-pubescent; rhizomes present or absent; stolons absent; corms absent; tubers absent. Roots not septate. Leaves sessile or petiolate; petioles triangular, rarely terete; blade with translucent markings as dots or lines present or absent, linear to lanceolate to ovate, base attenuate to cordate, margins entire or undulating, apex obtuse to acute. Inflorescences racemes or panicles, rarely umbels, of 1--18 whorls, erect or decumbent, emersed; bracts coarse, apex obtuse to acute, surfaces smooth or papillose along veins, apex obtuse to acute. Flowers bisexual, subsessile to pedicellate; bracts subtending pedicels, subulate to lanceolate, shorter than to longer than pedicels, apex obtuse to acute; pedicels ascending to recurved; receptacle convex; sepals recurved to spreading, herbaceous to leathery, sculpturing absent; petals white, entire; stamens 9--25; filaments linear, glabrous; pistils 15--250 or more, spirally arranged on convex receptacle, forming head, distinct; ovules 1; style terminal or lateral. Fruits plump, often longitudinally ribbed, sometimes flattened, rarely abaxially keeled, abaxial wings absent, lateral wings absent, glands often present.
Echinodorus are by nature marsh and bog plants that can grow submersed. Many species are grown in aquariums. They prefer good light and grow best in a deep, nutrient-rich substrate. Most will grow in variable water conditions, though the majority need tropical or sub-tropical temperature ranges. Propagation is by division or by new plants developing on submerged flowering stems. The larger species make magnificent specimen plants for the larger aquarium, though they may form aerial leaves in good conditions. If the inflorescence forms submerse small plantlets will form instead of flowers. If grown emerse and kept humid, flowers and seeds will normally readily form. The seeds can be grown in damp sand in warm, damp conditions. Additional CO2 often helps in strong growth.
Approximately 26 species distributed throughout the Western Hemisphere.
The genus Baldellia seems to be very closely related. note: in the latest revision by Karel Rataj 62 species, 2 subspecies and 2 varieties are listed. Many cultivars of uncertain taxonomic status are also listed by the aquarium trade.