Herbs, annual or perennial, aquatic, rooted in mud or free-floating. Stems of 2 types, vegetative and flowering; vegetative stems indeterminate, bearing many leaves, glabrous; flowering stems determinate, usually emersed, bearing single leaf, spathe, and terminal inflorescence. Leaves of 2 types, sessile and petiolate; stipule marcescent, apex truncate, associated with petiolate leaves only; sessile leaves submersed or rarely emersed, forming basal rosette or alternate on elongate stem, blade linear to occasionally oblanceolate, base sheathing, margins entire; petiolate leaves floating or emersed, blade cordate, reniform, or ovate. Inflorescences paniculate, spicate, umbellate, or 1-flowered; spathes bractlike, folded or clasping, commonly with acute to caudate extension. Flowers sessile, 3-merous; perianth with tepals connate proximally, yellow, blue, mauve, or white, tube tubular or funnelform, limb 6-lobed; stamens 3 or 6, adnate to perianth; pistils 3-locular, 1 or 3 developing to maturity; placentation parietal or basal; ovules 1–many. Fruits capsular or utriculate. Seeds smooth or with longitudinal wings.
Nearly worldwide, primarily of tropical and subtropical regions.
Genera 6, species ca. 30 (4 genera, 11 species in the flora; 2 genera, 3 species introduced).
|1||Inflorescences commonly with more than 50 flowers; fruits utriculate, 1-seeded||Pontederia|
|1||Inflorescences with fewer than 30 flowers; fruits capsular, 10–200-seeded.||> 2|
|2||Tepals connate only basally||Monochoria|
|2||Tepals connate 1/2 or more of their length.||> 3|
|3||Petiolate leaf blade coriaceous; perianth limb lobes ovate, longer than 2 cm; stamens 6||Eichhornia|
|3||Petiolate leaf blade membranous or absent; perianth limb lobes linear to oblanceolate, shorter than 2 cm; stamens 3||Heteranthera|