| waterlettuce | USDA PLANTS Symbol: PIST2 U.S. Nativity: Native Habit: Aquatic Forbs/Herbs |
| Pistia stratiotes L. |
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Taxonomic Rank: Liliopsida: Arales: Araceae |
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| 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. |
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Identification, Biology, Control and Management Resources
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| Selected Images from Invasive.org | View 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 & Kim Starr, Starr Environmental, Bugwood.org Additional Resolutions & Image Usage |
 Foliage; in water garden Forest & Kim Starr, Starr Environmental, Bugwood.org Additional Resolutions & Image Usage |
 Foliage; leaf Forest & 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 Alternative content
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 State(s) Where Reported invasive. Based on state level agency and organization lists of invasive plants from WeedUS database. Alternative content
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