water lettuce USDA PLANTS Symbol: PIST2
U.S. Nativity: Native
Habit: Aquatic Forbs/Herbs
Pistia stratiotes L.

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Taxonomic Rank: Liliopsida: Arales: Araceae
Synonym(s): tropical duckweed
Native Range: pantropical (GRIN);

Water lettuce is a free floating herbaceous plant that invades aquatic environments in the warmer regions of the United States. The leaves occur in a rosette and are gray-green, spongy, 0.8-6 in. (2-15 cm) long with deep, parallel veins. Flowering occurs in late summer to early winter, but plants have been observed flowering nearly all year. The inconspicuous flowers are clustered near the stalk. The fruit is a many-seeded, green berry. Water lettuce invades lakes, ponds and slow moving streams in tropical, subtropical and warmer temperate regions. High vegetative reproduction allows water lettuce to form dense floating mats of vegetation. Severe infestations block light to the water ecosystem, reduce oxygen levels, increase siltation, reduce suitable fish spawning habitat and restrict water flow and boating traffic. Water lettuce is believed to be native to Africa or South America, but it is widely distributed throughout the world’s tropical areas. The plant was identified in North America as early as the late 1700s.

Identification, Biology, Control and Management Resources

Selected Images from Invasive.orgView All Images at Invasive.org


Plant(s);
USDA Agricultural Research Service Archive, USDA Agricultural Research Service, Bugwood.org
Additional Resolutions & Image Usage

Foliage;
Graves Lovell, Alabama Department of Conservation and Natural Resources, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Plant(s); exotic invasive
Troy Evans, Great Smoky Mountains National Park, Bugwood.org
Additional Resolutions & Image Usage

Plant(s); in water garden
Forest and Kim Starr, Starr Environmental, Bugwood.org
Additional Resolutions & Image Usage

Foliage; in water garden
Forest and Kim Starr, Starr Environmental, Bugwood.org
Additional Resolutions & Image Usage

Foliage; leaf
Forest and Kim Starr, Starr Environmental, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Flower(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Infestation;
Karen Brown, University of Florida, Bugwood.org
Additional Resolutions & Image Usage

Infestation;
Karen Brown, University of Florida, Bugwood.org
Additional Resolutions & Image Usage

Infestation;
USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Infestation; Ichetucknee Springs State Park, Columbia/Suwannee counties, Florida, U.S.A.
Richard Carter, Valdosta State University, Bugwood.org
Additional Resolutions & Image Usage

EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org
 


State(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.

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Invasive Listing Sources:
Alabama Invasive Plant Council
Faith Campbell, 1998
Florida Exotic Pest Plant Council
John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
Mid-Atlantic Exotic Pest Plant Council, 2005