This widespread species of east-central states has a somewhat fragmented range, with centers in the central Appalachian region, southern Interior Low Plateaus, Ozarks, and upper midwest to southern Great Lakes. In Ky. it is usually associated with rocky woods on limestone, but some populations occur on sandstone (as in CRIT with loess above) or shale (as in LESL but probably base-rich). There is much variation in head size, ray development, overall pubescence and leaf shape; D. Estes (pers. comm.) is investigating potential segregates. Plants with much less pubescence have been tentatively segregated in Tenn. by D. Estes (pers. comm.), and may deserve variety status. Such plants do occur in Ky., for example at disturbed cliff bases in ROCK (37.3756 N, -84.3319 W).