Water chestnut

Scientific Name: Trapa natans

L.J. Mehrhoff, University of Connecticut, Bugwood.orgCopyright Info

Alfred Cofrancesco, U.S. Army Corps of Engineers, Bugwood.orgCopyright Info

Identification: The water chestnut is a rooted aquatic plant with submerged and floating leaves. The submerged leaves are feathery, while the floating leaves are glossy and triangle-shaped with toothed edges. The flower has four white petals, and the fruit is a large nut with four sharp spines. The plant is also known as European water chestnut, horned water chestnut, and water caltrop.

Size: Stems are typically 6-8 feet (2-2.5 m), but they can reach 16 feet (4.8 m) in length. Floating leaves are 0.75 to 1.5 inches (2-4 cm), and flower petals are 0.33 inch (0.85 cm) long.

Native Range: This plant is native to Europe, Asia, and Africa.

Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Trapa natans are found here.

Full list of USGS occurrences

State/ProvinceYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
New York1942201811Chaumont-Perch; Irondequoit-Ninemile; Lake Champlain; Lake Ontario; Lower Genesee; Mettawee River; Niagara; Oneida; Oswego; Salmon-Sandy; Seneca
Vermont194220143Lake Champlain; Mettawee River; Otter Creek

Table last updated 9/30/2019

† Populations may not be currently present.

Means of Introduction: This plant was first introduced to North America in the 1870s, where it was grown in a Harvard University botanical garden in 1877. Water chestnut escaped cultivation and was found growing in the Charles River by 1879. It was introduced into Collins Lake near Scotia, NY, around 1884. It may have been introduced intentionally to provide food for waterfowl or unintentionally as a water garden escapee. Once introduced, this plant spreads either by leaves breaking from the stems and floating to new areas, or more commonly by the nuts being carried by currents or waves.

Status: Water chestnut has been established in the northeastern United States since the late 1800s and can be found in New Hampshire, Massachusetts, Connecticut, Vermont, New York, Pennsylvania, Maryland, Virginia, and Quebec, Canada. It is established in Lake Ontario.

Remarks: An unrelated edible aquatic plant, Eleocharis dulcis, is also called water chestnut. Eleocharis dulcis is the familiar water chestnut, or Chinese water chestnut, sold in cans and commonly served in Chinese restaurants.

Author: Illinois-Indiana Sea Grant

Contributing Agencies:
NOAA Sea Grant GLRI Logo

Revision Date: 4/24/2012

Citation for this information:
Illinois-Indiana Sea Grant, 2019, Water chestnut: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatLakes/FactSheet.aspx?SpeciesID=263&Potential=N&Type=1&HUCNumber=, Revision Date: 4/24/2012, Access Date: 10/13/2019

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.