Mem. Torrey Bot. Club 5: 291. 1894. (as Pentstemon)
Herbs. Stems ascending to erect, (20–)35–80 cm, retrorsely hairy and glandular-pubescent, sometimes only glandular-pubescent distally, not glaucous. Leaves basal and cauline, not leathery, sparsely to densely pubescent, rarely glabrate; basal and proximal cauline 28–170 × 11–42 mm, blade orbiculate to obovate or elliptic, base tapered, margins irregularly crenate to irregularly serrate, apex rounded to obtuse; cauline 3–7 pairs, sessile or proximals short-petiolate, 28–170 × 9–40 mm, blade oblanceolate to lanceolate, proximals usually ± lyrate, base clasping or tapered, margins crenate to serrate, apex obtuse to acute. Thyrses interrupted, conic, (5–)8–23 cm, axis ± pubescent and glandular-pubescent, verticillasters 3–6, cymes 5–13-flowered, 2 per node; proximal bracts lanceolate, 8–60 × 2–20 mm, margins entire or ± crenate to serrate; peduncles and pedicels spreading to ascending, ± pubescent and glandular-pubescent. Flowers: calyx lobes lanceolate, 3.2–6(–7) × 1.4–1.8(–2) mm, sparsely to moderately glandular-pubescent; corolla lavender to purple, with lavender or purple nectar guides, ventricose, 20–30 mm, glandular-pubescent externally, ± white-pubescent internally abaxially, tube (4–)5–8(–10) mm, throat abruptly inflated, 5–8 mm diam., slightly 2-ridged abaxially; stamens included or longer pair reaching orifice, pollen sacs opposite, navicular, 1–1.5 mm, dehiscing completely, connective splitting, sides glabrous, rarely sparsely pubescent, hairs white, to 0.2 mm, sutures papillate; staminode (11–)14–22 mm, exserted, 0.5–0.7 mm diam., tip straight to slightly recurved, distal (7–)10–12 mm ± pubescent, hairs yellowish, to 2 mm; style 13–15 mm. Capsules 5–7 × 4–5 mm, glabrous. 2n = 16.
Phenology: Flowering (Apr–)May–Jul(–Sep).
Habitat: Woodlands, thickets, cliffs, barrens.
Elevation: 200–1600 m.
Ala., Ga., Ill., Ind., Ky., Md., N.C., Ohio, Pa., S.C., Tenn., Va., W.Va.
F. W. Pennell (1935) acknowledged that Penstemon canescens varies greatly in leaf size, flower size, and vestiture. He distinguished subsp. brittoniorum by its glabrate leaves with sharply serrate margins and dark purple corollas. Plants with those features are encountered mostly in the southern part of the range of the species, although they are essentially sympatric with subsp. canescens and sometimes in mixed populations with plants with the features of subsp. canescens.