Proc. Amer. Acad. Arts 6: 71. 1862. (as Pentstemon)
Herbs. Caudex rhizomelike. Stems decumbent, ascending, or weakly erect, 4–18 cm, retrorsely hairy, not glaucous. Leaves cauline, not leathery, glabrate, retrorsely hairy, or puberulent; cauline 2–4 pairs, petiolate or sessile, 7–28 × 3–12 mm, blade spatulate to oblanceolate, base tapered to clasping, margins entire, apex rounded or obtuse to acute. Thyrses interrupted or continuous, ± secund, 1–3 cm, axis ± glandular-pubescent, verticillasters 1 or 2(or 3), cymes 1- or 2-flowered, 1 or 2 per node; proximal bracts lanceolate, 17–23 × 4–10 mm, margins entire; peduncles and pedicels ascending to erect, retrorsely hairy and glandular-pubescent. Flowers: calyx lobes lanceolate, 6–10 × 1.3–2 mm, glandular-pubescent; corolla lavender or bluish lavender to lavender-purple, without nectar guides, bilabiate, not personate, tubular-funnelform, 15–20 mm, glandular-pubescent externally, densely white-lanate internally abaxially, tube 4–6 mm, throat gradually inflated, 5–6 mm diam., prominently 2-ridged abaxially; stamens included, pollen sacs opposite, subexplanate, 0.7–0.9 mm, dehiscing completely, connective splitting, sides glabrous, sutures smooth; staminode 8–9 mm, included, 0.3–0.4 mm diam., tip recurved, distal 4–5 mm moderately to densely lanate, hairs yellow, to 1 mm; style 11–12 mm. Capsules 6–8 × 4–5 mm, glabrous. 2n = 16.
Phenology: Flowering Jun–Aug.
Habitat: Alpine talus, gravel slopes, boulder fields.
Elevation: 3200–4200 m.
Penstemon harbourii is found on the high peaks of the Central Rocky Mountains. Populations have been documented in at least 17 counties. Habit, pubescence, and root characters of P. harbourii are somewhat anomalous in sect. Penstemon, prompting D. D. Keck (1945) to suggest possible ties with sect. Caespitosi or sect. Cristati. Molecular data appear to provide support for ties with sect. Caespitosi (A. D. Wolfe et al. 2006; C. A. Wessinger et al. 2016).