Tiedemannia filiformis (syn. Oxypolis filiformis) is a species of flowering plant in the carrot family known by the common names water cowbane and water dropwort.[1] It grows in swamps, freshwater wetlands, and along the borders of ponds in the southeastern United States, as far north as Delaware,[2] as well as the northern Bahamian pineyards of the Bahamas.[1]