This ranges widely over midwestern regions, centered in Iowa, Minn. and Wisc., but it is endangered or threatened in most states and still vulnerable even where it is most frequent, as in Iowa and Minn. (NS). In Ky. it is currently known from a few sites in the western (HARD) and northeastern (LEWI) Knobs; one plant may have been observed in LARU during 1986 by MM and JC. C. candidum occurs on seasonally dry soils in calcareous glades, but usually low on hillsides with some seepage in spring. Further west, C.W. Short collected it in the 1830s from "wet barrens near Hopkinsville" (CHRI at PH, KY; see also Short 1840, who stated: "This interesting species was first pointed out to me in the barrens of Christian county, by the Rev. Mr. Jones, of Hopkinsville..." At a relatively well-known site in HARD, there is clear evidence of introgression with pubescens (see colls at APSC), and there seems to have been continual digging of the whiter plants by orchid-addicts. At the nearby Jim Scudder Nature Preserve, a relatively large population, with over 100 plants during 1985-95, has greatly declined, which appears to have been caused by prescribed fires too late into the spring (T. Littlefield, pers. comm.). However, fires during the dormant season are generally thought to enhance the habitat for this species (Bowles 1983).