Water Lettuce
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Scientific Name
Pistia stratiotes - Visit ITIS for full scientific classification.
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Description
- Floating colonies with rosettes of ribbed, velvety, light green leaves.
- Leaves up to 2" wide and 6" long with squared or slightly indented tips.
- Inconspicuous flower spikes with separate male and female flowers.
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Habitat
- Still or slow-moving, warm, freshwater habitats, often with high nutrient levels.
- Does not tolerate freezing.
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Invasion Pathways and Distribution
- Introduced from tropical South America.
- Found worldwide in tropical areas.
- Can remove heavy metals from water but roots are killed by high levels of pollution.
- Sold as an ornamental pond or aquarium plant and used for medicine in Asia.
- It is spread by discarding plants from ponds and aquariums into waterways.
- In California it is found along the Colorado River and is expected to spread.
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Life History
- Seeds ripen in 4-6 weeks, need light to sprout, and can survive dry or freezing conditions.
- Also spreads by stolons (a type of stem) that produce new plants.
- Colonies become large and dense when conditions are right.
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Impacts
- Dense colonies reduce oxygen, light and pH levels in the water, outcompete other aquatic plants, interfere with water flow and recreational activities, increase siltation and provide mosquito habitat.
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References and Useful Links
For references by category and links to other useful AIS sites see our LEARN MORE page.