Penstemon linarioides var. sileri
Our plants belong to var. sileri A. Gray. Keck (Bull. Torrey Bot. Club 64: 373-375. 1937) distinguished the glabrous form in southwestern Utah and northern Arizona as var. viridis Keck. but leaf glabrosity appears in plants throughout the rang of var. sileri and is not her considered worthy of recognition. In the Paunsaugunt and Markagunt plateaus of eastern Washington Co. and western Kane Co., Utah and the Kaibab Plateau of Coconino Co., Arizona is a low form with the flowering stems decumbent at the base. This plateau form includes the types of both var. sileri and var. viridis, and may be more closely related to P. abietinus and P. crandallii than to true P. linarioides.
2n = 16
Holmgren NH. 1984. Penstemon and Keckiella. In Intermountain Flora, vol. 4. Ed. Arthur Cronquist et al. Bronx: The New York Botanical Garden.