Hort. Kew. 2: 361. 1789. (as Pentstemon laevigata)
Herbs. Stems ascending to erect, 40–115 cm, glabrous or retrorsely hairy, not glaucous. Leaves basal and cauline, basal sometimes withering by anthesis, not leathery, glabrous or puberulent; basal and proximal cauline 40–150 × 7–48 mm, blade oblanceolate to lanceolate, base tapered, margins entire or ± serrate, apex obtuse to acute; cauline 3–7 pairs, sessile or proximals sometimes petiolate, 18–128 × 8–28 mm, blade lanceolate, proximals sometimes oblanceolate, base clasping, sometimes tapered, margins entire or ± serrate, apex acute. Thyrses interrupted, narrowly conic, (3–)8–20 cm, axis glabrous or retrorsely hairy and sparsely glandular-pubescent, verticillasters 2–6, cymes (2–)4–11-flowered, 2 per node; proximal bracts lanceolate to linear, 8–38 × 1–3 mm, margins entire; peduncles and pedicels spreading or ascending, glabrous or retrorsely hairy and sparsely glandular-pubescent. Flowers: calyx lobes ovate, 3–6 × 1.5–2.1 mm, glabrous or glandular-pubescent; corolla pale lavender to violet, with reddish purple nectar guides, ventricose, 15–22 mm, glandular-pubescent externally, sparsely to moderately white-lanate internally abaxially, tube 5–6 mm, throat abruptly inflated, 5–8 mm diam., slightly 2-ridged abaxially; stamens included or longer pair reaching orifice, pollen sacs opposite, navicular, 1–1.2 mm, dehiscing completely, connective splitting, sides glabrous, sutures papillate; staminode 10–12 mm, exserted, 0.4–0.5 mm diam., tip straight to slightly recurved, distal 5–7 mm moderately to densely pubescent, hairs yellow, to 2.3 mm; style 12–15 mm. Capsules 5–8 × 3.5–5 mm, glabrous.
Phenology: Flowering May–Jun.
Habitat: Meadows, floodplain forests, fields, rock outcrops, calcareous bluffs.
Elevation: 10–400 m.
Ala., Conn., Del., D.C., Fla., Ga., Ky., La., Md., Mass., Miss., N.J., N.C., Ohio, Pa., S.C., Tenn., Va., W.Va.
Penstemon laevigatus primarily is a species of the Piedmont and eastern Appalachians; scattered populations occur outside those regions. L. La Cour (1931) reported a chromosome count of n = 48 for P. laevigatus. Without a voucher, it is impossible to know if this count was for the species as treated here, or P. calycosus or P. digitalis, which have been treated as infraspecific taxa of P. laevigatus.
An infusion made from Penstemon laevigatus is used by the Cherokee tribe of the southeastern United States as a gastrointestinal aid (D. E. Moerman 1998).