water lettuce
Pistia stratiotes L.


Pistia stratiotes is a sprawling, semi-woody shrub that invades wetlands in Florida. The green stems are up to 15 ft. (4.6 m) long and prickly.
Leaves are flashy and arranged in a rosette. They measure 0.75-6 in. (2-15 cm) in length. The leaves are green to grayish-green, and have dense white hairs and parallel veins on their surface. As its common name indicates, the plant resembles a floating head of lettuce.
This plant flowers year-round in southern Florida, but peaks during summer and early autumn.
The hydrosoil under a Pistia stratiotes infestation was shown to hold 4,196 seeds/m2. Mature seeds in fruits had an 84% germination rate.
Ecological Threat
Pistia stratiotes, forms extensive mats that can block navigational channels, impede water flow in irrigation and flood control canals, and disrupt submersed animal and plant communities (Sculthorpe, 1967; Attionu, 1976; Bruner, 1982; Sharma, 1984). Pistia stratiotes is among the world’s worst weeds (Holm et al., 1977). It has been placed on prohibited plant lists in Florida (FDEP, 2000), Louisiana (LDWF, 2000), Mississippi (MDAC, 1997), and Texas (TPWD, 2000), and is considered a noxious species (an invasive species of concern, but not regulated) in South Carolina (SCDNR, 2000) and Delaware (DDFW, 2000).


Selected Images


EDDMapS Distribution

EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org

State Regulated List

State Regulated List - This map identifies those states that list this species on their regulated list. For more information, visit Invasive.org

State Regulated List
   No Data for this state
   Troublesome or Common weed in one or more crops

Most Troublesome / Most Common Agricultural Weed List
This map identifies those states that consider this species either most troublesome or most common in at least one commodity. For more information, visit the MTMC project page.

Taxonomic Rank

Kingdom: Plantae
Phylum: Magnoliophyta
Class: Liliopsida
Subclass: Arecidae
Order: Arales
Family: Araceae
Genus: Pistia
Subject: Pistia stratiotes L.

Synonyms and Other Names

Other Common Names:
tropical duckweed


Plants - Aquatic Plants