This largely midwestern species is often confused with the largely eastern biennis, but it has a distinct genome (Dietrich et al., 1997). Colls. from CALL, DAVI, GRAV and HICK (MUR, SIU) have been referred to O. strigosa (Rydb.) MacKenzie & Bush, which has been treated as a more western subspecies of villosa, but these determinations appear to be erroneous (Dietrich et al. 1997). O. villosa is distinguished from biennis by its dense, largely appressed pubescence on stems and flowers (versus sparsely pubescent, and sometimes with longer spreading hairs as well as appressed). Its leaves are "dull green to gray-green" (versus "green to pale green").