The species is a variable annual of eastern and central North America (2n = 14, 28, 42). This largely northeastern and midwestern variety, as well as the southeastern var. pinnata, are typical of dry disturbed places. They appear widely scattered along cliffs, trails, roads or railroads with dry base-rich soils. In Ky. their status remains uncertain: both may be native or considered waifs from afar. The more western var. intermedia (Rydb.) Hitchc. may also be expected as a waif (FNA 7, W).