Proc. Amer. Acad. Arts 16: 106. 1880. (as Pentstemon)
Herbs or subshrubs. Stems ascending to erect, 15–45 cm, retrorsely hairy, hairs pointed, not glaucous. Leaves cauline, opposite or subalternate, retrorsely hairy, hairs pointed, not glaucous; cauline 4–8 pairs, short-petiolate or sessile, 16–70 × 1–8(–14) mm, blade lanceolate to linear, base tapered, margins entire, apex obtuse to acute. Thyrses interrupted, cylindric, 4–15 cm, axis puberulent or retrorsely hairy, verticillasters 3–10, cymes 1–5(–7)-flowered, 2 per node; proximal bracts lanceolate to linear, 7–50 × 1–6 mm; peduncles and pedicels ascending to erect, puberulent or retrorsely hairy. Flowers: calyx lobes ovate, 3–5.5 × 1.4–2.3 mm, glabrous or sparsely puberulent; corolla blue to violet or purple, without nectar guides, ampliate, 16–21 mm, glabrous externally, glabrous internally, tube 4–5 mm, throat gradually inflated, 5–6 mm diam., slightly 2-ridged abaxially; stamens included, filaments glabrous, pollen sacs parallel, 1–1.5(–1.8) mm, distal 1/2–2/3 indehiscent, sides hispidulous, hairs white, to 0.1 mm near filament attachment, sutures denticulate, teeth to 0.1 mm; staminode 10–12 mm, reaching orifice or barely exserted, 0.5–0.7 mm diam., glabrous; style 11–13 mm. Capsules 6–7 × 4.5–6 mm. 2n = 16.
Phenology: Flowering May–Jul.
Habitat: Rocky, often basaltic, sagebrush shrublands.
Elevation: 600–1500 m.
Penstemon cusickii is known from west-central and southwestern Idaho (Ada, Blaine, Canyon, Elmore, Gem, Owyhee, and Washington counties) and eastern Oregon (Baker, Grant, Harney, Malheur, Union, and Wheeler counties).