Gen. N. Amer. Pl. 2: 52. 1818.
Herbs. Caudex herbaceous. Stems ascending to erect, (15–) 20–50 cm, retrorsely hairy and glandular-pubescent, not glaucous. Leaves basal and cauline, not leathery, glabrous or sparsely, rarely densely, puberulent; basal and proximal cauline 25–75 × 4–15 mm, blade ovate to oblanceolate or lanceolate, base tapered, margins subentire or ± serrate, apex obtuse to acute; cauline 4–7 pairs, sessile, 25–80 (–90) × (2–) 4–10 (–15) mm, blade lanceolate to linear, base truncate to clasping, margins entire or serrulate to serrate, apex acute to acuminate. Thyrses interrupted, sometimes continuous, cylindric, (3–) 5–17 (–21) cm, axis glandular-pubescent, verticillasters (2 or) 3–5 (–7), cymes 2–6-flowered, 2 per node; proximal bracts lanceolate, 5–95 × 1–12 mm, margins entire or serrulate, rarely serrate; peduncles and pedicels ascending to erect, glandular-pubescent. Flowers: calyx lobes ovate to lanceolate, 4–6 × 1.5–2 mm, glandular-pubescent; corolla light lavender to lavender, with violet nectar guides, tubular, 14–22 mm, glandular-pubescent externally, moderately white-pilose internally abaxially, tube 4–6 mm, throat slightly inflated, 4–6 mm diam., prominently 2-ridged abaxially; stamens included, pollen-sacs divergent, navicular, 1–1.3 mm, dehiscing completely, connective splitting, sides glabrous, sutures papillate; staminode 11–12 mm, reaching orifice, 0.4–0.5 mm diam., tip slightly recurved, distal 7–9 mm densely villous, hairs golden yellow, to 1.5 mm; style 9–12 mm. Capsules 6–8 × 3–4 mm, glabrous. 2n = 16.
Phenology: Flowering May–Aug.
Habitat: Tallgrass, mixed grass, and shortgrass prairies, foothills.
Elevation: 300–2100 m.
Alta., B.C., Man., Ont., Sask., Colo., Ill., Ind., Iowa, Mich., Minn., Mont., Nebr., N.Mex., N.Dak., S.Dak., Wis., Wyo.
Glabrous-leaved plants are characteristic on the prairies of most of the central and northern Great Plains, and in the foothills of the Central, Northern, and Canadian Rocky mountains. Puberulent-leaved plants from the Driftless Area of Wisconsin have been named var. wisconsinensis. Puberulent-leaved plants also occur in Alberta and in North Dakota (specimens from Barnes, Benton, Eddy, Pierce, Ramsey, Wells, and Williams counties have been seen), sometimes with glabrous-leaved plants. Penstemon gracilis is introduced in Indiana (K. Yatskievych 2000).
The roots of Penstemon gracilis are used by the Lakota of the northern Great Plains for protection from snakebites (D. E. Moerman 1998).
"/4+timescorollathroat" is not declared as a valid unit of measurement for this property.