Brittonia 31: 105. 1979.
Stems ascending to erect, (9–)15–32 cm, retrorsely hairy. Leaves basal and cauline, not leathery, glabrous or retrorsely hairy; basal and proximal cauline petiolate, 20–85 × 4–8(–12) mm, blade oblanceolate to lanceolate, base tapered, margins entire or obscurely dentate, apex obtuse; cauline 2 or 3 pairs, sessile, 30–75 × 3–10 mm, blade lanceolate, base tapered to clasping, margins entire, apex acute. Thyrses interrupted, cylindric, 5–18 cm, axis glandular-pubescent, verticillasters 3–7, cymes 2–5-flowered, 2 per node; proximal bracts lanceolate, 5–38 × 2–10 mm; peduncles and pedicels glandular-pubescent. Flowers: calyx lobes lanceolate, (2.2–)4.5–7.5 × (0.9–)1.2–1.6 mm, glandular-pubescent; corolla violet or blue, with reddish violet nectar guides, weakly bilabiate, funnelform, 8–12 mm, sparsely yellow-lanate or glabrous internally abaxially, tube 4–5 mm, throat gradually inflated, not constricted at orifice, 2–5 mm diam., rounded abaxially; stamens included, pollen sacs opposite, explanate, 0.6–1 mm, dehiscing completely, sutures smooth; staminode 6–8 mm, included, 0.3–0.6 mm diam., tip recurved, distal 3–5 mm sparsely to densely pubescent, hairs yellow, to 1 mm; style 3–4 mm. Capsules 4.5–6.5 × 4–5 mm.
Phenology: Flowering May–Jun.
Habitat: Clayey and gravelly soils, sagebrush shrublands.
Elevation: 1600–2000 m.
Penstemon marcusii is found in the San Rafael Swell and along the eastern edge of the Wasatch Plateau in Carbon and Emery counties, Utah. The species is most similar to P. goodrichii, differing primarily in its puberulent stems and smaller flowers.