Stems ascending to erect, (17–)30–80 cm, glabrous, not or ± glaucous. Leaves basal and cauline, ± leathery or not, glabrous, ± glaucous; basal and proximal cauline 50–170 × 8–25(–35) mm, blade oblanceolate to elliptic, base tapered, margins entire, apex obtuse to acute; cauline 3–7 pairs, sessile or proximals short-petiolate, (15–)30–90(–120) × (4–)8–25 mm, blade lanceolate to ovate, base cordate-clasping or proximals tapered, apex acute. Thyrses continuous or interrupted, secund, (3–)7–27 cm, axis glabrous, verticillasters (3–)5–14, cymes (2 or)3–6-flowered, 2 per node; proximal bracts lanceolate, 15–65 × 2–26 mm; peduncles and pedicels glabrous, peduncles to 18 mm, pedicels 3–18 mm. Flowers: calyx lobes obovate to ovate, 2.5–4.5 × 2–3.4(–3.8) mm, apex mucronate, sometimes acute to acuminate, glabrous; corolla blue to violet or purple, without nectar guides, ventricose, 24–30(–34) mm, glabrous externally, glabrous internally, tube 7–10 mm, throat gradually inflated, not constricted at orifice, 8–11 mm diam., slightly 2-ridged abaxially; stamens: longer pair reaching orifice, pollen sacs divergent, sigmoid, 1.8–2.7(–3) mm, dehiscing incompletely, proximal 1/5 indehiscent, connective not splitting, sides hispid to hispidulous, hairs white or tan, to 0.2 mm, sutures denticulate, teeth to 0.1 mm; staminode 14–17 mm, included, 0.5–0.7 mm diam., tip straight, distal 4–7 mm sparsely pilose, hairs yellow, to 1 mm; style 17–23 mm. Capsules 9–13 × 5–7 mm.
Phenology: Flowering Jun–Aug.
Habitat: Gravelly or sandy hillsides, sagebrush shrublands.
Elevation: 1400–2900 m.
Idaho, Mont., Wyo.
Penstemon cyaneus occurs from the vicinity of Yellowstone National Park westward into south-central Idaho.