The Water Chestnut (Trapa natans) also known as water nut, water caltrop, and bull nut, are an Invasive Species to North America. Originally from Eurasia and Africa, they are now common in the waters of the northeast United States in places like New York, Massachusetts, and Rhode Island to name a few.
History of Water Chestnut:
The water chestnuts have been a source of nutrition since the Neolithic period. Today, it is still grown in China and India. It was introduced to the United States in the mid-1800s. While labeled a nuisance species in the United States, the water chestnut is protected in Europe.
Water Chestnut Appearance:
On the water the leaves of the Water Chestnut plant look like a cluster of large floating green parsley. Below the surface, there are long roots that dangle and float down to the muddy bottom of the water. The size of the plant can be around 16 feet.
The fruit or nut is devilish in appearance. The shell of the nut is smooth and black. It is dark and horned, the horns appear at four corners and act like spikes. The nut is small, about an inch or two in size.
Water Chestnut Habitat:
Water Chestnuts can be found in all types of bodies of water. The Hudson River is full of them as is the Housatonic River in Connecticut, Charles River in Massachusetts and Passaic River in New Jersey. The ideal depth for the Water Chestnut is around 3 meters, which means they are likely located closer to the shore in the bodies of water they inhabit.
Lasting Impacts:
The water chestnut has some features that greatly impact their environment. A few are listed below:
–Limit amount of light entering water – This kills other species of plants who can’t grow through the Water Chestnut overgrowth
-Growth near the surface and shore obstructs water activities– this prevents boaters, fishermen/women, and swimmers from being able to enjoy the waterway.
–Sharp horned fruit are dangerous– can choke wildlife or penetrate the skin of people attempting to enjoy the water without foot protection.
– Oxygen depletion– harms fish population by lowering the quality of the water for other aquatic species
Water Chestnut Sighting:
I saw a few water chestnuts when I was hiking along the Hudson River in the Black Creek Preserve Trail. They were strewn about on the shores and looked like dried out horned skeletons along the beach. I could see why you would want to protect your feet if you were in an area this species grew in.
Species Spotlight:
| Common name | Water Chestnut: aka water nut, water caltrop, and bull nut |
| Species | Trapa natans |
| Location Spotted | Black Creek Preserve, Hudson River, Esopus, New York |
| Date Spotted | January 11th, 2023 |
| Sighting and Trail Remarks | Hiking in the Black Creek Preserve I headed toward the Hudson River where there were a few beaches and look out points along the trail. While there, I noticed little horned black nuts along the banks of the river. These were remnants of the invasive water chestnut that would blanket the banks come spring. |