This hexaploid (2n = 54) is probably derived from the northeastern diploid, radula. It was discovered during the 1980s in LAUR and PULA along the Rockcastle River (Campbell & Medley 1989), and then along the Big South Fork of Cumberland Rv. in Ky. (MCRE) and Tenn. (Scott Co.). More robust plants tend to have narrower leaves, denser heads, and paler flower color (usually white versus blue); these may be associated with more open sites. Despite some initial signs, no significant differences in plants have been found between the two rivers. Luc Brouilllet (FNA 20) and Alan Weakley (W) have claimed that an i should be dropped from the end of saxicastellii, but their reasons are not clearly explained.