This is widespread in western and southern regions of North America, and it probably occurred in native grasslands of w. Ky. before settlement, although its original distribution is somewhat uncertain. S. obtusata is now generally uncommon, even in good grassland remnants, but it seems to have spread locally along roads and railroads into more eastern regions. It often appears to behave as an annual, unlike other species in the genus. Some plants have been referred var. lobata (Trin.) Scribn. and var. pubescens (Scribn. & Merr.) Scribn., but these taxa are not generally recognized in recent treatments (e.g. FNA 24). See also S. intermedia, which has been confused.