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 approximately 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 in its family that occurs north of Florida. They tend to be associated with wet soils, many growing in shallow water, in
wetlands, or in wet savannas like
flatwoods. In wet soils, their abundance appears to be related to water levels, fire frequency, and competition from other plants such as grasses. Experiments have shown that they are weak competitors compared to many other wetland plant species. Some species can persist as buried seeds during unfavorable conditions. ==Selected species==