Fl. Amer. Sept. 2: 738. 1813.
Stems ascending, (10–) 50–65 (–80) cm, glabrous or puberulent to pubescent, not glaucous. Leaves basal and cauline, or basal absent or reduced, not leathery, glabrous or puberulent to pubescent, not glaucous; basal and proximal cauline 20–80 (–155) × 5–20 (–45) mm, blade obovate to oblanceolate or lanceolate, base tapered, margins entire, usually undulate, apex obtuse to acute, sometimes mucronate; cauline (2 or) 3–6 (–8) pairs, sessile, 27–120 (–150) × (6–) 22–35 (–43) mm, blade lanceolate, base truncate to cordate, apex obtuse to acute. Thyrses continuous, secund, (3–) 6–26 (–30) cm, axis glabrous or puberulent, verticillasters (3–) 5–12, cymes 2–4-flowered, 2 per node; proximal bracts ovate to lanceolate, 14–100 × 2–36 mm; peduncles and pedicels glabrous or puberulent, peduncles to 71 mm, pedicels 4–14 mm. Flowers: calyx lobes ovate to orbiculate, 2–11 × 1.3–5.5 mm, glabrous or puberulent; corolla blue to violet, with reddish purple nectar guides, ventricose, 24–48 mm, glabrous externally, glabrous internally or sparsely to moderately white-lanate internally abaxially, tube 5–12 mm, throat gradually inflated, slightly constricted at orifice, 8–13 (–18) mm diam., rounded abaxially; stamens included or longer pair reaching orifice, pollen-sacs divergent, navicular, 1.4–2.5 (–2.8) mm, dehiscing incompletely, connective not splitting, sides sparsely to moderately hirsute, hairs white or tan, to 0.5 mm, rarely glabrous, sutures denticulate, teeth to 0.2 mm; staminode (15–) 18–22 mm, included or barely exserted, 0.6–1.3 mm diam., tip straight to recurved, rounded to distinctly bifurcate at apex, glabrous or distal 1–2 mm sparsely lanate, hairs pale-yellow, to 1.5 mm; style 18–20 mm. Capsules 10–17 × 5–8 mm.
Colo., Mont., N.Dak., N.Mex., Nebr., S.Dak., Wyo.
Varieties 3 (3 in the flora).
The Penstemon glaber complex has been treated with as many as four species (F. W. Pennell 1920b) or one variable species as treated herein. M. K. W. Latady (1985) found clinal variation in most morphologic characters used to distinguish taxa in the complex and recognized only one species and two varieties: var. glaber (including var. alpinus) in the plains and mountains from southeastern Montana south to central Colorado; and var. brandegeei, in the mountains from central Colorado south to north-central New Mexico. A case for recognizing var. alpinus, as is done here, can be made on morphological, phenological, and ecological grounds.
|1||Calyx lobes 2–4.8 mm, apices rounded or abruptly short-acuminate; staminode apices rounded.||Penstemon glaber var. glaber|
|1||Calyx lobes 3.8–11 mm, apices long-acuminate; staminode apices rounded or bifurcate.||> 2|
|2||Staminode apices rounded or bifurcate; corollas 24–35 mm; stems glabrous or puberulent proximally.||Penstemon glaber var. alpinus|
|2||Staminode apices usually bifurcate; corollas 27–48 mm; stems puberulent to pubescent proximally.||Penstemon glaber var. brandegeei|
"/4+timescorollathroat" is not declared as a valid unit of measurement for this property.