water lettuce
(Pistia stratiotes)
This species is Native and Introduced across its range in the United States
Native Range
Tropical Americas, Asia, Malesia, and Australia
Appearance
Waterlettuce is a free-floating aquatic perennial that resembles a floating head of lettuce. Plants have feathered roots as well as stolons that produce daughter plants. Leaves are fleshy, wedge-shaped, 1–6 in (2½– 15 cm) long, and covered with dense water repellent hairs. The inflorescence is an inconspicuous spadix with a ring of 6–8 male flowers and one female flower below. They are enclosed by a hairy white spathe. Fruits are very small green berries.
Impact
Waterlettuce forms dense mats that displace native species, impede water flow and water navigation, destroy fish spawning habitat, alter water nutrient cycling, reduce production in rice paddies, impede hydroelectricity production, and damage water recreational sectors.
Reference
Dray, F.A. and P.T. Madeira. 2022. Waterlettuce (Pistia stratiotes): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2022-23- WATERLETTUCE-P. https://bugwoodcloud.org/resource/files/23229.pdf
Resources
- Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
- Global Invasive Species Database - Invasive Species Specialist Group
- Images, Video and Information - University of Florida - Center for Aquatic and Invasive Plants
- Fact Sheet - Ontarios Invading Species Awareness Program
Selected Images
Maps
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 Lists - This map identifies those states that have this species on their invasive species list or law.
Invasive Listing Sources
- Alabama Invasive Plant Council - Watch list A
- Alabama Noxious Weeds - Class C Noxious Weed
- Alachua County Cogongrass Initiative
- Apalachicola Invasive Working Group
- Connecticut Invasive Plant Working Group
- Florida Invasive Plant Council - Plant List - Category I
- Florida Noxious Weeds
- Invasive Species of Concern in Georgia
- John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
- Maryland Aquatic Nuisance Species Plan
- Maryland Department of Natural Resources Policy: Restriction on Planting Exotic Invasive Plants
- Maryland Invasive Species Council - Invasive Species of Concern in Maryland
- Michigan’s Invasive Species Watch List
- Mid-Atlantic Field Guide to Aquatic Invasive Species
- National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
- New Hampshire Invasive Species Committee. 2005. Guide to Invasive Upland Plant Species in New Hampshire. New Hampshire Department of Agriculture, Markets and Food Plant Industry Division and New Hampshire Invasive Species Committee.
- New Jersey Invasive Species Strike Team 2017 Invasive Species List
- Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
- Ontario’s Invading Species Awareness Program Tracked Species List
- South Carolina Illegal Aquatic Plants
- South Carolina Invasive Pest Council
- South Carolina Plant Pest List
- WeedUS - Database of Plants Invading Natural Areas in the United States
- Wisconsin Noxious Weeds
- Wisconsin's Invasive species rule – NR 40
Taxonomic Rank
| Domain: Eukarya |
| Kingdom: Plantae |
| Phylum: Magnoliophyta |
| Class: Magnoliopsida |
| Superorder: Lilianae |
| Order: Alismatales |
| Family: Araceae |
| Genus: Pistia |
| Pistia stratiotes |
Other System Links
Plants: PIST2
Bayer: PIIST
GRIN: 102491
ITIS: 42542
NPDN Pest: PAKAEBA
NPDN Host: 36229
References
Common Name Reference: USDA, NRCS. 2010. The PLANTS Database. National Plant Data Center, Baton Rouge, LA, USA.
Scientific Name Reference: USDA, NRCS. 2010. The PLANTS Database. National Plant Data Center, Baton Rouge, LA, USA.