Ruppia cirrhosa is a species of aquatic plant known by the common names spiral ditchgrass and spiral tasselweed. It is native to the Americas and Europe, where it grows in freshwater bodies, such as lakes. It is a thread-thin, grasslike perennial herb which grows from a rhizome anchored in the wet substrate. It produces a long, narrow inflorescence tipped with two tiny flowers. As the fruit develops the peduncle of the inflorescence curls into a neat spiral.