Spring 2009

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Weed it & Reap

Have You Seen This Weed?

European Water Chestnut


Alias:  Trapa natans, Water Nut

japanese barberry



Last Seen: While this plant is relatively rare in its native habitat in Europe, it is forming dense floating mats on some parts of the Lower Susquehanna River, in areas around Philadelphia, parts of the upper Delaware River and in a few isolated lakes in Pennsylvania (as well as other northeastern states).

Description: This aquatic plant can reach up to 15 feet in lentgh. Floating leaves grow in a dense rosette pattern and have a saw-tooth edge. Small four-petaled, white flowers form in the middle of the leaf rosettes in June. Four spines stick out of the nut, making this a treacherous plant to come across as a barefooted swimmer. And because these nuts can remain viable for up to 12 years, this is a long-lasting problem plant.

Jessica holding a box turtle

Caution: The European water chestnut is NOT related to the edible water chestnut, used in Chinese cuisine. Not only is the plant not edible, its TOXIC!

Don't let this plant drive you nut-ty! With nuts that can puncture shoe leather, this plant is a real "pain." But thankfully there are ways to get rid of it before it grows out of control. To learn more about water chestnut management and its impact on the Chesapeake Bay, visit the website:
Water Chestnut Management Plan

-- Text & illustration by Jessica Sprajcar, Conservation Programs Manager,, DCNR Office of Conservation Science




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