Penstemon virgatus var. asa-grayi
Stems glabrous. Leaves glabrous. 2n = 16.
Phenology: Flowering Jun–Sep.
Habitat: Sandy or gravelly roadsides and hillsides, oak woodlands, pine woodlands.
Elevation: 1400–3000 m.
Colo., N.Mex., Wyo.
Variety asa-grayi is known from the Front Range of the Southern Rocky Mountains. The variety is encountered from Albany and Laramie counties in southeastern Wyoming, south to Mora County, New Mexico. A specimen from Sublette County, Wyoming, likely is from an introduction. Variety asa-grayi sometimes grows in mixed populations with Penstemon strictus, although the two species can be distinguished immediately by their pollen sacs, which are lanate and divergent in P. strictus and glabrous and opposite in P. virgatus.
The name Penstemon unilateralis Rydberg, a synonym of P. secundiflorus, was widely misapplied to this taxon in much of the 1900s; F. S. Crosswhite (1965f, 1967c) clarified and corrected the situation.