Pistia is a genus of aquatic plant in the arum family, Araceae, comprises of a single species Pistia stratiotes.
Pistia stratiotes is often called water cabbage, water lettuce, Nile cabbage, or shellflower. Its native distribution is uncertain, but probably pantropical; it was first discovered from the Nile near Lake Victoria in Africa. It is now present, either naturally or through human introduction, in nearly all tropical and subtropical fresh waterways. The genus name is derived from the Greek word pistos, meaning water, and refers to the aquatic nature of the plants.
Photos: HortPark, Singapore 20120323