in J. M. Coulter and A. Nelson, New Man. Bot. Rocky Mt., 449. 1909. (as Pentstemon)
Herbs or subshrubs. Stems ascending to erect, 40–90 cm, glabrous, glaucous. Leaves cauline, opposite, glabrous, glaucous; cauline 6–14 pairs, sessile, 30–85(–102) × 3–13 mm, blade elliptic, base tapered, margins entire, apex acute. Thyrses interrupted, cylindric, 6–30 cm, axis glabrous, verticillasters (5–)8–14, cymes 1(or 2)-flowered, 2 per node; proximal bracts narrowly elliptic to linear, 8–45 × 1–8 mm; peduncles and pedicels ascending to erect, glabrous. Flowers: calyx lobes obovate to ovate or elliptic, 1.8–3.2 × 1.5–2.2 mm, glabrous or minutely ciliolate distally; corolla light lavender to violet or purple, with violet nectar guides, weakly ventricose, 22–26(–28) mm, glabrous externally, glabrous internally, tube 7–9 mm, throat gradually inflated, 7–9 mm diam., 2-ridged abaxially; stamens included or longer pair exserted, filaments glabrous, pollen sacs parallel to slightly divergent, 1.5–2 mm, distal 2/3 indehiscent, sides glabrous, sutures denticulate, teeth to 0.1 mm; staminode 15–16 mm, included, 0.5–0.6 mm diam., glabrous; style 16–20 mm. Capsules 7–10 × 4.5–5.5 mm.
Phenology: Flowering Jun–Aug.
Habitat: Rocky to gravelly and talus slopes, Gambel oak, maple, and aspen woodlands.
Elevation: 1200–2300 m.
Penstemon sepalulus is found in the Wasatch Mountains in Juab, Sevier, Utah, and Washington counties.