Water Chestnut

Trapa natans

Water chestnut is a harmful invasive species that has:

• Triangle- or diamond-shaped leaves that form rosettes that float on the surface of the water.
• Leaves that are three-quarters of an inch to 1.5 inches long, toothed around the edges and have a shiny upper side and fine hairs underneath.
• Thread-like leaves that grow alternately on submerged portions of the leaf stalks.

Water chestnut can be free-floating or rooted to bottom sediments.

Where does water chestnut grow?

Water chestnut is found in slow-moving fresh and brackish waters. It grows in muddy, fine-grained sediments. Water chestnut is particularly prevalent in the Bird, Bush and Sassafras rivers on Maryland's Eastern Shore.

How does water chestnut reproduce?

Water chestnut can reproduce sexually when:

• Plants, which flower in June and July, are pollinated by insects.
• The white flowers elongate and harden to form barbed spikes on the fruit.
• Seeds stay viable for up to 12 years.
• Each seed creates 15 to 20 rosettes and each rosette can create up to 20 seeds.

Asexual reproduction can take place during the growing season if an intact rosette breaks away from a plant.

Other facts about water chestnut:

• Water chestnut is a harmful invasive species. It was introduced from Eurasia in the 1800s. Today the plant is rare in the Bay due to eradication efforts. Any water chestnut sightings should be reported to the Maryland Department of Natural Resources at (410) 260-8630.
• Technically classified as floating aquatic vegetation (FAV), rather than submerged aqautic vegetation (SAV), because its leaves float on the water's surface.