The European water chestnut (Trapa natans) was introduced to North America in the 1870s, when it was cultivated as an ornamental in the botanical garden of Harvard botanist Asa Gray. Within a few years' time, the plant was growing wild in the Charles River, and it has since gained a reputation for being an aquatic nuisance plant with particularly aggressive growth habits. According to one source, water chestnut spreads by seed or by any fragment of the plant that floats or is carried to a new location.
This summer, water chestnut plants clogged the water around the new floating docks in Henry Hudson Riverfront Park. On Thursday morning, a Gossips reader witnessed a crew from the Department of Public Works clearing out the water chestnut, but their technique may not have been one that the Department of Environmental Conservation would encourage. The eyewitness reported that the crew, working from a boat, were raking the leafy mats of the plant that float on the surface and dragging them out into the river, just short of the navigation channel, where the current would carry them downstream.