This aggressive rhizomatous weed is widespread in cool temperate and southern boreal regions of North America. It was not recorded in Ky. until about 1900. In 1914 Gm noted: "not as common in Kentucky as it is farther north and west. It has been noted at Lexington, and has been sent me once or twice from Western Kentucky." Also, Anderson (1924) stated in was "scarce." After 1930 it has gradually become widespread and locally abundant, especially in some old pastures or lawns where it may have been promoted; the species often becomes locally dominant in seasonally damp swales at these such sites. The appropriate treatment for variation within repens remains uncertain (FNA 24). Most plants are hexaploid (2n = 42), with a complex origin. Segregates have not been generally recognized in North America, but F and others have suggested that plants along the north Atlantic coast, and perhaps adventive inland, may be treated as a native taxon: A. repens (L.) Beauv. var. subulatum (Schreb.) Roemer & J.A. Schultes (?= A. pungens noted in FNA 24). The coll. from MCRA (MUR) has been referred to var. subulatum forma setiferum Fern.