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Anchored water hyacinth (Eichhornia azurea); Water hyacinth, floating (Eichhornia crassipes)

A floating perennial herb that is native to South America introduced as an ornamental into the US in 1884. It can grow quickly, forming dense mats which restrict light to the underwater environment.


Regulated areas of Water Hyacinth
These species are Prohibited (Red counties)

Other names for this plant include:

  • Common names: water orchid, floating water hyacinth
  • Scientific names: Pontederia crassipes, Eichhornia speciosa

Ecological threat:

  • Invades freshwater lakes, reservoirs, ponds, marshes and ditches making boating, fishing, and almost all other water activities difficult.
  • Degrades water quality by blocking the air-water interface and greatly reducing oxygen levels in the water, impacting underwater animals such as fish.
  • Greatly reduces biological diversity: mats block sunlight, preventing growth of submerged and emersed plant communities and also alter animal communities by blocking access to the water and/or reducing plants the animals depend on for shelter and nesting.

Classification in Wisconsin: Prohibited

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for water hyacinth was based upon these literature reviews: Eichhornia azurea [PDF], Eichhornia crassipes [PDF].


Leaves: Thick green waxy leaves, rounded, circular or elliptical in shape with gently incurved sides. Leaves are formed in rosettes and get to be 6” wide and can rise between 1- 3 feet above water.

Flowers: Lavender blue with a yellow blotch. Flowers have 6 petals and are 2 inched wide.

Fruits & seeds: Three celled capsule with many seeds.

Roots: Submersed roots blue black to dark purple, feathery, dense near root crown, tips with long dark root caps.

Similar species: May be confused with emergent form of frog's-bit, Limnobium spongia.


Counties in WI where water hyacinth has been reported (as of April 2013). Both vouchered and unvouchered reports included.

Do you have water hyacinth in your county but it isn't shaded on the map? Have you seen it? Send us a report.


Mechanical: Very small populations can be controlled by pulling. Physical removal should be completed before flowering and seed set.

Chemical: Registered aquatic herbicides can provide temporary control of water hyacinth in small scale applications. 2,4 D or glyphosate can be effective. Application of aquatic herbicide requires a permit.

Biological: Biological control options: Neochetina eichhorniae, N. bruchi (weevils), and Niphograpta albiguttalis (moth larvae) have been used in tropical and subtropical populations. No known biological controls have been tested in Wisconsin.


View water hyacinth pictures in our photo gallery!


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Last revised: Friday May 31 2019