Pistia

Scientific name

Pistia L.

Common names

water lettuce

Family

Araceae

Could be confused with

unlikely to be confused with any other genus

Native distribution

information not available, possibly South America or Africa

Species commonly cultivated

Pistia stratiotes L. (pan-tropical)

Adventive distribution

most tropical and subtropical regions of the world

Weed status

noxious weed in numerous countries around the world

Habit

floating, stoloniferous rosette plant

Brief description

Perennial, stoloniferous, free-floating. Leaves in rosette, sessile or short-petiolate; leaf blade obovate, emarginate and sometimes undulate apically, densely pubescent, filled with aerenchyma for floatation, venation parallel. Roots numerous, long, pinnately branched. Inflorescence a small spadix borne on a short, axillary peduncle; spathe green, hairy, tubular below, open above, constricted between male and female parts of spadix; spadix reduced, fused to spathe on one side. Dispersal by seed.

Natural habitat

still waters of most water bodies

Additional comments

Pistia is a highly distinctive genus that consists of a single species, P. stratiotes. The origin of Pistia is speculative, with suggestions that it originated in Africa or North America, based on historical records and fossils. Based on the preponderance of insect herbivores that originate from South America that feed on this plant, it is more plausible that this is the actual origin. Pistia is widely traded as a pond plant and under high nutrient conditions can quickly dominate a water body as a dense, floating monoculture.