Bull. S. Calif. Acad. Sci. 38: 12. 1939.
Herbs. Stems ascending to erect, 60–150 cm, glaucous. Leaves: basal and proximal cauline 37–110 × 10–50 mm, blade obovate, base tapered, margins coarsely serrate to coarsely dentate, apex obtuse to acute; cauline 4–8 pairs, sessile, 40–110 × 15–55 mm, blade ovate, base connate-perfoliate, margins coarsely serrate to coarsely dentate, apex acute to acuminate. Thyrses interrupted, secund, 16–90 cm, axis glandular-pubescent, verticillasters 9–23, cymes 1–4-flowered; proximal bracts ovate to lanceolate, 8–25 × 3–28 mm; peduncles and pedicels ascending to erect, glandular-pubescent. Flowers: calyx lobes ovate, 4–6 × 2.2–3 mm, glandular-pubescent; corolla pink to rose-pink, purple, or light yellow, with or without reddish or reddish purple nectar guides, strongly bilabiate, ventricose, 18–27 mm, glandular-pubescent externally, glandular-pubescent internally, and sparsely white or yellowish lanate internally abaxially, tube 7–10 mm, length 1.7–2 times calyx lobes, throat abruptly inflated, constricted at orifice, 6–9 mm diam., rounded abaxially; stamens: longer pair reaching orifice, filaments of shorter pair glandular-puberulent proximally, pollen-sacs explanate, 1.4–1.8 mm, sutures smooth; staminode 14–16 mm, included or exserted, 0.3–0.4 mm diam., tip recurved, distal 4–5 mm lanate, hairs yellow, to 2.8 mm, proximal 3–4 mm glandular-puberulent; style 14–16 mm, glabrous. Capsules 10–13 × 5–7 mm, glabrous or sparsely glandular-pubescent distally.
Phenology: Flowering Mar–Jun.
Habitat: Gravelly soils, arroyos, roadsides, talus slopes, desert scrub, juniper woodlands.
Elevation: 500–1700 m.
Ariz., Calif., Nev.
Penstemon bicolor is known from the Mojave Desert in the Black Mountains of northwestern Mohave County, Arizona, the Castle, Clark, and New York mountains of eastern San Bernardino County, California, and the desert mountain ranges of southern and western Clark County, Nevada. Two subspecies differing in corolla color have been recognized, with yellow-corolla forms restricted to Clark County, Nevada. Subspecies are not recognized here, following J. D. Morefield (2006).
Habitat destruction and genetic swamping caused by hybridization between Penstemon bicolor and P. palmeri threaten many populations of P. bicolor in the vicinity of Las Vegas, Nevada (G. Glenne 2003).
Glenne, G. 2003. Reproductive Biology, Hybridization Isolating Mechanisms, and Conservation Implications of Two Rare Subspecies of Penstemon bicolor (Brandeg.) Clokey and Keck: Ssp. bicolor and ssp. roseus Clokey and Keck (Scrophulariaceae) in Clark County, Nevada. M.S. thesis. Utah State University.
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