This occurs mostly in hilly regions of east-central states, especially on mesic to submesic sites on sandy soils in or around the Apppalachians and Ozarks. It is virtually absent in the Bluegrass region and in lowlands of the lower Ohio and central Mississippi Valleys. In the central Bluegrass, Short (1828-9) noted: "...found on the rocky or gravelly margins of the larger water-courses. Kentucky river." Variation in Iris cristata is evident at the molecular level (Hannan & Orick 2000), but deserves further study in relation to morphology and habitat; 2n = 24 and 32 (FNA 26, Y). Plants occur locally on the dry crests of calcareous cliffs (e.g. in ESTI and HART); are these distinct genetically from more plants in more typical habitats?