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Invasive Freshwater Plants and Algae

Water Hyacinth

  • Scientific Name

    Eichhornia crassipes - Visit ITIS for full scientific classification. 

  • Description


    • Floating waterweed, may root in mud, forms dense mats.
    • Leaves smooth, rounded or tapered to a blunt point, leaf stalks spongy and inflated or tapered.
    • Leaf blades up to 6" wide and stalks 12" or more long.
    • Stolons (a type of stem) link plants, forming clumps or mat.
    • Plant up to 16" high.
    • Flower stalk up to 20" high with many pale blue, purple or white flowers. 
  • Habitat
    • Still or slow-moving, warm, freshwater habitats with high nutrient levels and pH (3) 4-6.
    • Tolerates salinity below 1.6%. 
  • Invasion Pathways and Distribution
    • Believed to have been introduced from South America.
    • Also occurs in Central America.
    • In California it is found in the San Joaquin Valley and in Los Angeles, San Bernardino and Riverside Counties.
    • Pieces of mats break off and can infest new areas. 
  • Life History
    • Can flower and produce seeds as soon as plant is 3-4 weeks old.
    • Also reproduces by stolons (a type of stem) that spread and produce new plants. 
  • Impacts
    • Grows rapidly and is difficult to control.
    • Dense mats cover large area of open water, reduce habitat for other plants and animals, provide mosquito habitat, reduce oxygen levels in the water, and interfere with navigation, recreation, water flow, water pumping and delivery.
    • California State Parks - Division of Boating and Waterways conducts a control program in the Sacramento-San Joaquin Delta. 
  • References and Useful Links

    For references by category and links to other useful AIS sites see our LEARN MORE page.