Eriocaulon is a genus of about 400 species commonly known as pipeworts, of monocotyledonous flowering plants in the family Eriocaulaceae. The genus is widely distributed, with the centers of diversity for the group occurring in tropical regions, particularly southern Asia and the Americas. A few species extend to temperate regions, with ca. 10 species in the United States, mostly in the southern states from California to Florida, and only two species in Canada; China has 35 species, also mostly southern. Only one species (E. aquaticum) occurs in Europe, where it is confined to the Atlantic Ocean coasts of Scotland and Ireland; this species also occurs in eastern North America and is thought to be a relatively recent natural colonist in Europe. In the Americas, Eriocaulon is the only genus