This annual (2n = 30) of rocky glades and prairies occurs mostly in the northern Great Plains and midwest, but with scattered populations extending east onto calcareous sites in the Appalachians (K, W). Eastern plants are largely restricted to dry calcareous glades or associated remnants of native grassland, especially on the dolomitic foothills of the Knobs. A. Cusick's coll. from BATH (NCU) comes from Sand Road (Ky. 1269) west of Hedrick Church, together with another rare plant, Orbexilum onobrychis. On Mississippian limestone, is also a coll. from the "Cave Run Botanical Area" in BATH (KNK), and it has also been found along the White Oak Cliffs in ESTI (JC).