Brittonia 50: 162, fig. 1A–E. 1998.
Herbs. Stems ascending, 7–20(–28) cm, retrorsely hairy, hairs appressed, white, scalelike, not glaucous. Leaves cauline, opposite, glabrous abaxially, glabrate or retrorsely hairy, hairs appressed, white, scalelike, adaxially, not glaucous; cauline 4–7 pairs, short-petiolate or sessile, 17–35 × 3–7 mm, blade oblanceolate to lanceolate, proximals sometimes spatulate, base tapered, margins entire, apex rounded to obtuse or acute. Thyrses interrupted, secund, 1–11 cm, axis glandular-pubescent distally, sometimes also retrorsely hairy proximally, hairs appressed, white, scalelike, verticillasters 2–5(–7), cymes 1- or 2(or 3)-flowered, 2 per node; proximal bracts lanceolate, 4–26 × 1–7 mm; peduncles and pedicels ascending to erect, glandular-pubescent. Flowers: calyx lobes ovate to lanceolate, 3.5–5.5(–6.5) × 1.7–2.1 mm, glandular-pubescent; corolla violet to reddish purple, without nectar guides, funnelform, 14–18 mm, glandular-pubescent externally, glabrous internally, tube 5–6 mm, throat gradually inflated, 4.5–6 mm diam., 2-ridged abaxially; stamens included or longer pair reaching orifice, filaments glabrous, pollen sacs parallel, 0.9–1.2 mm, distal 1/2–2/3 indehiscent, sides glabrous, sutures denticulate, teeth to 0.1 mm; staminode 7–8 mm, exserted, 0.4–0.6 mm diam., glabrous; style 10–13 mm. Capsules 6–9 × 4–5 mm. 2n = 16.
Phenology: Flowering Jun–Aug(–Sep).
Habitat: Talus slopes and crevices, limestone, pine and subalpine conifer woodlands.
Elevation: 3000–3500 m.
Penstemon rhizomatosus is known only from the Schell Creek Range of White Pine County. The species occurs near the summits of Cave Mountain, Cleve Creek Baldy, and Taft Peak (N. H. Holmgren 1998).