Bot. Gaz. 54: 147. 1912. (as Pentstemon)
Herbs. Stems ascending to erect, 30–70 cm, ± retrorsely hairy, not glaucous. Leaves essentially cauline, basal leaves absent or poorly developed, not leathery, glabrous, sometimes ± puberulent; cauline 4–8(–10) pairs, sessile, 30–90 × 4–17 mm, blade lanceolate, base tapered, margins entire, apex acute. Thyrses continuous or interrupted, cylindric, (1–)2–15 cm, axis ± retrorsely hairy, verticillasters 1–5, cymes (2–)6–13-flowered, 2 per node; proximal bracts lanceolate to linear, 8–38 × 1–8 mm, margins entire; peduncles and pedicels ascending to erect, glabrous or retrorsely hairy. Flowers: calyx lobes broadly ovate to obovate or elliptic, 1.7–3 × 0.9–2 mm, apex obtuse to acute or slightly cuspidate, glabrous; corolla violet to blue or purple, with faint reddish purple nectar guides, funnelform, 12–15 mm, glabrous externally, densely yellow-villous internally abaxially, tube 3–4 mm, throat gradually inflated, 3–4 mm diam., 2-ridged abaxially; stamens included or longer pair slightly exserted, pollen sacs opposite, explanate, 0.4–0.8 mm, dehiscing completely, connective splitting, sides glabrous, sutures smooth; staminode 6–8 mm, included, 0.2–0.3 mm diam., tip straight to slightly recurved, distal 2–3 mm sparsely to densely villous, hairs yellow, to 0.7 mm; style 7–9 mm. Capsules 4.5–6 × 2.5–3.5 mm, glabrous.
Phenology: Flowering Jun–Jul.
Habitat: Dry meadows, sagebrush shrublands.
Elevation: 1700–2400 m.
Penstemon laxus is known from south-central Idaho; populations are known in Blaine, Boise, and Elmore counties.