Although this species occurs widely in Appalachian regions and nearby hills, it was not generally recognized until Small's description in 1894. Rafinesque's (1836, 2:26-27) "rupestris" may have been grandis, collected "On the cliffs of the River Kentucky"; but see Nesom (2009) and notes under illinoensis. In Ky. some western records of grandis need to be rechecked for possible transitions to illinoensis, which overlaps with grandis in s. Ind. (Heikens 2003) and c. Ky. (e.g. the colls. from BREC at KY). However, almost all colls. from the Ky. Rv. Palisades are clearly grandis, without transitions to illinoensis. O. grandis and illinoensis appear relatively close to macrantha, colorea, perhaps texana and perhaps florida (Nesom 2009, Nesom et al. 2014). Compared to more weedy species (stricta, dillenii, corniculata), grandis and allies have generally larger flowers, with red lines on the petals, and tristylous variation (or distylous in macrantha), in contrast to homostylous or slightly heterotylous in the more weedy group. The only reported chromosome counts are 2n = 28 for grandis and perhaps 16 in florida; in the more weedy group, reported counts are mostly 2n = 18-24 and 36-48.