Contr. W. Bot. 12: 63. 1908. (as Pentstemon)
Stems ascending to erect, 20–60 cm, glaucous, sometimes not. Leaves glabrous, glaucous; basal and proximal cauline 28–100 × 2–11 mm, blade oblanceolate to elliptic, base tapered, margins entire, apex obtuse to acute; cauline 3–6 pairs, sessile, (11–)30–80(–120) × 2–9 mm, blade lanceolate to linear or linear-subulate, base clasping to auriculate-clasping, margins entire, apex rounded to acute. Thyrses interrupted, cylindric, 6–26 cm, axis glabrous, verticillasters 5–9, cymes 1–4-flowered; proximal bracts lanceolate to linear, 6–33 × 1–4 mm; peduncles and pedicels erect, glabrous. Flowers: calyx lobes ovate to lanceolate, 2–4.5 × 1.4–2.1 mm, margins entire or erose, glabrous or ± glandular along margins; corolla scarlet, without nectar guides, nearly radially symmetric, weakly bilabiate, salverform, 18–26 mm, glabrous externally, glabrous internally, tube 4–7 mm, 1.6–3 times as long as calyx lobes, throat slightly inflated, 3–5 mm diam., rounded abaxially; stamens: longer pair reaching orifice, pollen sacs explanate, 0.7–0.9 mm, sutures smooth; staminode 13–14 mm, essentially terete, 0.1 mm diam., tip straight, glabrous, rarely distal 1–2 mm sparsely papillate, papillae yellow, to 0.2 mm; style 10–19 mm. Capsules 6–8 × 4–5 mm. 2n = 16.
Phenology: Flowering (Feb–)Mar–May.
Habitat: Rocky slopes, mesas, canyons.
Elevation: 500–1300 m.
Penstemon subulatus has been documented in Gila, Graham, Maricopa, Mohave, Pinal, and Yuma counties in central Arizona.