water chestnut

Myrtales > Trapaceae > Trapa natans L.
Synonym(s): water nut

Water chestnut is a rooted, floating plant that invades shallow to deep, fresh water habitats in the northeastern United States. Water chestnut can grow in 12 to 15 ft. (3.6-4.6 m) of water and forms dense, floating mats, often three layers deep. Leaves on the surface of the water are alternate, triangular in shape, strongly toothed and connected to the stem by an inflated petiole. Submerged leaves are feathery and either opposite or alternate. Flowering occurs from mid-summer to frost. Small, four-petaled flowers give way to the nut-like fruit. The fruit have two to four, 0.5 in. (1.3 cm) long, sharp, barbed spines. The spines can penetrate shoes. The dense, floating mats restrict light availability, reduce the oxygen content, and displace other emergent and floating vegetation. Water chestnut also limits boating, fishing, swimming and other recreational activities. Water chestnut is native to Europe and Asia and was first observed in the United States in Massachusetts in the late 1800s.


Identification, Biology, Control and Management Resources


Selected Images from Invasive.org

Click on each thumbnail to download the image at 1536x1024 resolution or below for available resolutions.
Use 768x512 for Microsoft PowerPoint and use 1536x1024 for Prints and Publications.

Plant(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
768x512

Flower(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
768x512 / 1536x1024

Fruit(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
768x512

Fruit(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
768x512

Feature(s); single rosette showing horned fruits and the inflated leaf petioles which enables the rosette to float
Alfred Cofrancesco, U.S. Army Corps of Engineers, Bugwood.org
768x512 / 1536x1024

Plant(s); Floating rosettes
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
768x512 / 1536x1024

Infestation; on Lake Champlain, New York
Alfred Cofrancesco, U.S. Army Corps of Engineers, Bugwood.org
768x512 / 1536x1024

Infestation;
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
768x512

Fruit(s);
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
768x512 / 1536x1024

Diagram or Graphic; Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 2: 612.
USDA PLANTS Database, USDA NRCS PLANTS Database, Bugwood.org
768x512 / 1536x1024

Invasive Reference(s):

Check Invasive.org for most current lists.
  • Alabama - Noxious Weed Law
  • Arizona - Noxious Weed Law
  • Maine - Noxious Weed Law
  • Massachusetts - Noxious Weed Law
  • North Carolina - Noxious Weed Law
  • Oregon - Noxious Weed Law
  • South Carolina - Noxious Weed Law
  • Vermont - Noxious Weed Law
  • Virginia - Invasive Alien Plant Species
  • Washington - Noxious Weed Law
  • Mid-Atlantic - EPPC List
  • Invasive Plant Atlas of New England


External Links


footer line
USDA Forest Service Bugwood University of Georgia