Water hyacinths (Eichhornia crassipes) are sometimes sold in garden centers as a water garden plant due to their floating habit and pleasing purple flowers. But in the wild, water hyacinths are a noxious weed capable of covering a pond with a dense mat of growth. Water hyacinths are free-floating plants with trailing roots. The plant can be found in temperate climates throughout the world. There are several methods to remove water hyacinths from a pond.
Hand-scoop water hyacinths from the edge of the pond or using a boat. This method works best before the plant can spread over a wide area. If you remove water hyacinths manually, you must remove every plant for this to be effective. If the dense mat of water hyacinths breaks up, individual plants will continue to reproduce. Clean the boat before leaving the boat ramp. This will help you to avoid spreading the plants from pond to pond, or re-infecting your clean pond with new plants.
Transport removed water hyacinths to a disposal center. Disposal centers use chopping machines to render water hyacinths into slurry that they can spray back into the water for recycling.
Release mottled water hyacinth weevils, chevroned water hyacinth weevils or Argentine water hyacinth moth into your pond. These insects feed on water hyacinth in their larval and adult forms. The weevil have a life cycle of 120 days, and quickly die afterward. Moths have a life span of 30 days. You can purchase weevils from organic weed and pesticide companies. Typically, weevils are shipped in egg form glued to cards. To release the bugs, leave the cards out. As the weevils hatch, they leave the cards and seek out water hyacinths on which to feed.
Stock your pond with hyacinth-eating animals, such as white Chinese geese. The geese will consume hyacinth, along with other invasive plants such as water chestnuts.
Sprinkle your pond with a granulated weed killer formulated for killing aquatic plants such as 2,4-D, diquat or glysophate. Granulated weed killers may also kill desirable plants in the pond as well, and may upset the ecosystem of the pond. As hyacinth that covers pond surfaces die, they can use up the oxygen in the water and may kill all of the fish in the pond as well.