What is European Water Chestnut?

Illustration by Pam Burns from *Aquatic Plants of New England Series: Trapa natans, Crow and Hellquist 1983*

The water chestnut is an annual aquatic plant not native to the United States, categorized as an invasive species in the Connecticut River Watershed. The water chestnut is a rooted, floating aquatic plant. It has rosettes of leaves that float on the surface of the water that appear to be radiating from a central point. They are triangular or slightly diamond shaped, toothed on two sides and connected to the stem by a long, flexible submerged stalk. Submerged leaves are feathery and either opposite or alternate. Very small, white four-petaled flowers bloom in July. The seeds are four-horned nut-like structures  that mostly develop on the underside of the floating rosette. Seeds ripen in about a month (ripe seeds start to drop around the end of July or early-mid August).These seeds remain viable for up to twelve years. One seed can produce up to 15 rosettes, producing up to 20 more seeds, and quickly covering the water surface.

What is the problem? Why is it an invasive plant?

The water chestnut hogs space and nutrients, preventing other plants and animals from living there. The decomposition of foliage decrease amounts of dissolved oxygen which severely damages fish and other aquatic life’s ability to survive. Then there’s the fruit–the spiny seeds hurt if stepped on! Water chestnut infestations also impede fishing, hunting, swimming and boating as the rosettes cover entire bodies of water up to sixteen feet deep. Management of out of control infestations is costly! However, this plant can be kept in check and prevented from invading new ponds and coves by removing plants before they have a chance to set seeds.

How can I help?


The good news about this plant is that it is easy to identify and can be managed by trained volunteers. Together, we can do something about it!

Learn how to identify and report water chestnut as well as when it appropriate to pull the plants, how to properly pull them and how to properly dispose of the pulled plants. We will come talk to your organization! Contact us at crc@ctriver.org to schedule a presentation.