Penstemon scariosus var. garrettii
"Although P. scariosus exhibits a complex range of variability, the specimens more or less sort into the three weakly recognizable varieties. Each is geographically distinct. The Blue Mountain collections appear consistently to have glandular-pubescent corollas, a character that sporadically occurs throughout the range of the species, but never as noticeably so. This is a character found in closely related and sympatric P. subglaber, which differs by its taller growth habit, less scarious calyx-margins, and anthers bearing shorter pubescence. The anther-cells of P. subglaber spread 180 degrees apart from each other, whereas they spread apart at about a 90 degree angle in P. scariosus." (Intermountain Flora - N.H. Holmgren)
Holmgren NH. 1984. Penstemon and Keckiella. In Intermountain Flora, vol. 4. Ed. Arthur Cronquist et al. Bronx: The New York Botanical Garden.