Water chestnut (Trapa natans) is a rooted submerged aquatic plant that quickly forms dense floating mats and outcompetes native plant communities. Its decay can deplete oxygen levels, leading to fish kills. Dense growths can interfere with swimming and entangle propellers, which hinders boating, fishing, and waterfowl hunting. In mid-July, small white flowers appear on rosettes at the water's surface. When fruits form, they become submerged and dangle beneath the rosettes. These woody chestnuts develop four sharp spines and wash ashore where they can be hazardous for swimmers and walkers, and can even puncture bike and ATV tires.
Native to Europe, Asia and Africa, water chestnut was first discovered in North America in the late 1800s, imported as a showy water garden plant. It escaped to New Hampshire, Connecticut, Massachusetts, New York, Vermont, and Rhode Island. It spreads by rosettes, woody seeds, and plant pieces that break off and float on water currents. Water chestnut can spread to new waters through improper disposal by water gardeners and by clinging to watercraft. Controlling established water chestnut infestations is costly. Your actions and your help in reporting new infestations are vital for preventing their spread.
Learn to recognize water chestnuts.