Penstemon glaber var. alpinus
Proc. Amer. Acad. Arts. 6: 60. 1862. (as Pentstemon)
Stems glabrous or puberulent proximally. Flowers: calyx lobes ovate, 3.8–9.5 × 1.3–3.3 mm, apex long-acuminate; corolla 24–35 mm, sparsely to moderately white-lanate internally abaxially; staminode apex rounded or bifurcate. 2n = 16.
Phenology: Flowering Jun–Aug(–Sep).
Habitat: Sandy or gravelly slopes and banks in shortgrass prairies, foothills, mountains.
Elevation: 1500–2900 m.
Colo., Nebr., N.Mex., Wyo.
Variety alpinus occurs in the Front Range of the Rocky Mountains on gravelly, granitic slopes, and roadcuts. The type of Penstemon magnus Pennell, on which P. alpinus subsp. magnus is based, was collected in Jackson County, Colorado. The specimen is in poor condition but has calyx lobes to 8 mm with apices short- to long-acuminate; it is tentatively assigned here.