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Water Chestnut

Counties in which water chestnut has been identified

Water chestnut is an aquatic invasive plant that is native to Eurasia and Africa. It was introduced in the United States in the mid-1800's as an ornamental plant. Around 1884, water chestnut was found growing in Collins Lake near Scotia, NY. Water chestnut colonizes areas of freshwater lakes and ponds and slow-moving streams and rivers and negatively impacts aquatic ecosystems and water recreation.

Where Is Water Chestnut Found?

Water chestnut is found in forty-three counties in New York: Albany, Bronx, Broome, Cattaraugus, Cayuga, Chautauqua, Chemung, Chenango, Clinton, Columbia, Dutchess, Erie, Essex, Greene, Jefferson, Madison, Monroe, Montgomery, Nassau, Niagara, Onondaga, Oneida, Ontario, Orange, Oswego, Otsego, Putnam, Rensselaer, Rockland, Saratoga, Schenectady, Schoharie, Schuyler, Seneca, Steuben, Suffolk, Sullivan, Tompkins, Ulster, Washington, Wayne, Westchester, and Yates. Many of the infestations are reported in or near the Hudson River.

How Do I Identify Water Chestnut?

Rosette of water chestnut leaves floating on water

Water chestnut is an annual plant with a submerged stem 12-15 feet long that has fine roots that anchor it to the soil. Its floating leaves are triangular in shape with saw-toothed edges and hollow air-filled stems. Leaves form a rosette around a central point. Its flowers generally bloom in June and are four-petaled and white. Its fruits are hard nuts with four inch spines that have barbs along them. Seeds within fruits can remain viable for up to 12 years.

How Does It Spread?

Spiny water chestnut nutlets in hand

Water chestnut spreads by rosette and fruits detaching from the stem and floating to another area. They also spread by clinging to floating objects including recreational watercraft, the pads of boat trailers, and fishing equipment.

Why Is It A Problem?

Water chestnuts form dense mats of rooted vegetation that can be very difficult to get through in a boat, kayak, canoe, or when swimming. Water chestnut fruits are often found along the shoreline and bottom of waterways - they have very sharp spines with barbs that can cause painful wounds when stepped on. The dense mats of vegetation shade out native aquatic plants that provide food and shelter to native fish, waterfowl, and insects. Decomposition of these dense mats reduces dissolved oxygen levels and may kill fish. Property values along shorelines of infested waters may also decrease.

Dense mat of water chestnut plants

What Are The Tools For Management?

Water chestnut can be controlled using manual, mechanical, and chemical methods. As with all other infestations, early detection is key for containing and controlling spread. The smaller the size of the infestation, the more easily it can be eradicated and its economic and ecological impacts reduced. Hand-pulling when rosettes first appear (mid-June to early July) is an effective way to control spread and reduce the size of infestations. This method can become prohibitive if the infestation covers a large area. For larger infestations, as in Lake Champlain, harvesting machines are used. Applications of aquatic herbicides approved for use in New York can also be effective. Because the fruits remain viable for up to twelve years in the sediment, it will take several years for both mechanical and chemical methods to be fully effective. NYSDEC is currently funding research on biocontrol - a study of the effectiveness of predator insects from water chestnut's native range in control the spread of water chestnut.

What Can I Do To Help?

Prevention is the most effective method for dealing with invasive species. If they are never introduced, they never become established.

  • Clean, drain, and dry your watercraft, trailer, and equipment before and after each use. Regulation 6 NYCRR Part 576 requires everyone who uses watercraft on public waters to, when possible, use the following methods to fully decontaminate your equipment:
    • Clean the outside of the watercraft and trailer with high pressure (2500 psi) hot water (140F) for 10 seconds.
    • Flush the inside of the motor and all compartments (bilge, live well, bait buckets, ballast, etc.) with hot water (140F) for two minutes.
    • Soak fishing gear and equipment in hot water (140F) for two minutes.
  • Dump bait bucket water where it came from or on land.
  • View more information on how to clean your boat.

Early detection of infestations helps to reduce removal costs and ecological impacts

  • If you think you've found water chestnut please take several photos and submit a report to iMapInvasives.
  • Become a Chestnut Chaser! We know that water chestnut is underreported in New York State. Each summer we encourage folks to survey their favorite swimming holes, lakes, ponds, and nearby waterbodies for water chestnut and submit reports to iMapInvasives.
  • Share the water chestnut fact sheet (PDF, 300 KB) with others.