Europe is home to only three species: "D. intermedia", "D. anglica", and "D. rotundifolia". Where the ranges of the two latter species overlap, they sometimes hybridize to form the sterile "D. × obovata". In addition to the three species and the hybrid native to Europe, North America is also home to four additional species; "D. brevifolia" is a small annual native to coastal states from Texas to Virginia, while "D. capillaris", a slightly larger plant with a similar range, is also found in areas of the Caribbean. The third species, "D. linearis", is native to the northern United States and southern Canada. "D. filiformis" has two subspecies native to the East Coast of North America, the Gulf Coast, and the Florida panhandle.