Pacif. Railr. Rep. Parke, Bot., 15. 1856. (as Pentstemon)
Stems 20–40 cm, glabrous or glabrate. Leaves 10–20 pairs, 5–32 × 0.3–2 mm, blade base tapered, margins glabrous or scabrous, apex acuminate to mucronate. Thyrses 2–15(–23) cm, verticillasters (2–)5–10(–30), cymes 1- or 2-flowered; proximal bracts linear, 3–22 × 0.2–1 mm; peduncles and pedicels glabrous or scabrous. Flowers: calyx lobes ovate, 1–2.7 × 0.9–1.5 mm; corolla lavender to violet, lined internally abaxially with reddish purple nectar guides, funnelform, 8–14 mm, glandular-pubescent internally in 2 lines on abaxial surface, sometimes also in sinuses of adaxial lobes, tube (1.5–)2–3 mm, throat 3–5 mm diam.; stamens included or longer pair reaching orifice or barely exserted, pollen sacs 0.4–0.5 mm; staminode 5–6 mm; style 7–9 mm. Capsules (4–)5–8 × 3–4 mm. 2n = 16.
Phenology: Flowering Apr–Aug(–Sep).
Habitat: Sandy or rocky slopes, chaparral, creosote shrublands, pine-juniper woodlands.
Elevation: 500–1200(–2100) m.
Ariz., Calif., Nev., N.Mex., Tex., Utah, Mexico (Baja California, Chihuahua).
Plants of Penstemon thurberi from northern Clark County, Nevada, with corollas 8–9 mm and capsules 4–5 mm have been treated as var. anestius.