Pistia is a genus of aquatic plant in the arum family, Araceae. The single species it comprises, Pistia stratiotes, is often called water cabbage, water lettuce, Nile cabbage, or shellflower.It is an invasive plant in tropical and sub-tropical regions.
Dr Abe V Rotor
Living with Nature - School on Blog (avrotor.blogspot.com)
Paaralang Bayan sa Himpapawid (People's School-on-Air) with Ms Melly C Tenorio
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Kiapo, photo by Dr Abe V Rotor
Pistia stratiotes, as this floating plant is scientifically called, may cover an entire stream or waterway. It must have been abundant on the Pasig River in the area where Quiapo is located, hence the name of the district. In the same manner, Manila is derived from the name of a plant, maynilad a cat-tail of the genus Typha and Family Cyperaceae. The plant must have covered much of the shores and swampy areas of Pasig River.
Summary of Invasiveness
P. stratiotes is a perennial monocotyledonous aquatic plant present, either naturally or through human introduction, in nearly all tropical and subtropical fresh waterways. It floats on the water surface, with roots hanging below floating leaves. Its growth habit can make it a weed in waterways, where it can kill native submerged plants and reduce biodiversity. It is a common aquatic weed in the USA, and may clog waterways in warmer states such as Florida. It is listed as a noxious weed or invasive aquatic plant in some states of the USA (USDA-NRCS, 2012).