Water Chestnut
Trapa natans

Appearance

The water chestnut's triangular or diamond-shaped leaves form rosettes that float on the water’s surface. The leaves have teeth along the edges, a shiny upper side and fine hairs underneath. Thread-like leaves grow alternately along the submerged part of the stem.

Tiny, white flowers bloom in June to July. Hard, greenish-brown fruits with four sharp spikes are attached to the plant’s underside in spring and early summer. Water chestnut can float freely or be rooted to bottom sediments.

Reproduction and Life Cycle

Water chestnut can reproduce both sexually and asexually. Sexual reproduction takes place in early summer. After being fertilized, female flowers mature into fruit-bearing shoots. The shoots eventually break off, releasing their seeds as they float on the surface.

Asexual reproduction takes place when the rhizome (underwater portion of the plant's stem) grows and winter buds, called "turions," form.

Did You Know?

• It is believed that water chestnut was introduced in the mid-1800s for ornamental use in ponds.
• Water chestnut is considered to be invasive because it blocks sunlight from reaching bay grasses and can impede boat navigation. The plant’s sharp, spiky fruits are dangerous to humans swimming or walking on beaches.

Sources and Additional Information

• Underwater Grasses in Chesapeake Bay & Mid-Atlantic Coastal Waters by Maryland Sea Grant
• PLANTS Database: Trapa natans – USDA Natural Resources Conservation Service
• Plant Invaders of Mid-Atlantic Natural Areas: Water Chestnut – National Park Service