BugwoodWiki Article

European water chestnut
Trapa natans L.


Trapa natans is a rooted, floating plant that invades shallow to deep, fresh water habitats in the northeastern United States. It can grow in 12-15 ft. (3.6-4.6 m) of water and forms dense, floating mats, often three layers deep.
The rosette of leaves on the surface of the water are alternate, triangular in shape, strongly dentate (toothed) and connected to the stem by an inflated petiole. Submerged leaves are feathery and either opposite or alternate.
Trapa natans has small, four-petaled flowers that bloom from July to frost.
The nut-like fruit has two to four, 0.5 in. (1.3 cm) long, sharp, barbed spines. They ripen in about a month and can remain viable as long as 12 years. Each seed can produce 1-15 rosettes and each rosette can produce as many as 20 seeds. The spines can penetrate shoes.
Ecological Threat
The dense, floating mats of Trapa natans restrict light availability, reduce the oxygen content, and displace other emergent and floating vegetation. It also limits boating, fishing, swimming and other recreational activities. Trapa natans is native to Europe and Asia and was first observed in the United States in Massachusetts in the late 1800s.


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EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org

EDDMapS Distribution

State Invasive List - This map identifies those states that list this species on their invasive species list. For more information, visit Invasive.org

State Invasives List

Invasive Listing Sources

Taxonomic Rank

Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Rosidae
Order: Myrtales
Family: Trapaceae
Genus: Trapa

Other System Links

Plants: TRNA
Bayer: TRPNA
GRIN: 36824
ITIS: 27170

Synonyms and Other Names

Other Common Names:
water chestnut, water nut


Category: Aquatic