any of several genera of aquatic plants comprising the family Pontederiaceae, especially those of the genus Pontederia. Most species are perennials, native primarily to tropical America. They have creeping rootstocks, fibrous roots, and leaves in clusters at the base of the plant or borne on branched stems. The fruit is a capsule containing many seeds, or a one-seeded winged structure. Plants of the genus Pontederia, about five species of perennials, have spikes of bluish-purple flowers at the top of a one-leaved stem, clusters of lance- or heart-shaped leaves at the base, and thick rootstocks.

Pickerelweed (P. cordata) is common in shallow lakes and muddy shores in eastern North America. It is sometimes cultivated as an ornamental garden pool or aquarium plant. water hyacinth (Eichhornia) and mud plantain (Heteranthera) are other widely distributed genera of the family.