Pacif. Railr. Rep. Parke, Bot., 15. 1856.
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-flowered 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), Mexico (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.
"/4+timescorollathroat" is not declared as a valid unit of measurement for this property.