Subshrubs. Stems ascending to erect, 30–150 cm, glabrous or retrorsely hairy, hairs pointed, rarely glaucous. Leaves essentially cauline, basal absent or essentially so, opposite, glabrous or retrorsely hairy to puberulent, hairs pointed, rarely glaucous; cauline 5–11 pairs, petiolate or sessile, 10–100 × 0.5–12 mm, blade oblanceolate to lanceolate or linear, base tapered to clasping, margins entire, apex acute. Thyrses interrupted or continuous, cylindric, (6–)10–32 cm, axis glabrous or retrorsely hairy, verticillasters (3–)5–14, cymes 1(–3)-flowered, (1 or)2 per node; proximal bracts lanceolate to linear, 5–65 × 0.5–5 mm; peduncles and pedicels ascending to erect, glabrous or retrorsely hairy. Flowers: calyx lobes obovate to oblanceolate or ovate to lanceolate, 2.6–6(–7) × 1.3–3.3 mm, glabrous or puberulent; corolla blue to violet or purple, without nectar guides, ventricose to ventricose-ampliate, 24–38 mm, glabrous externally, glabrous internally, tube 7–10 mm, throat gradually inflated, 8–11 mm diam., 2-ridged abaxially; stamens included or longer pair reaching orifice or slightly exserted, filaments glabrous, pollen sacs parallel, 2.2–3 mm, distal 1/3–1/2 indehiscent, sides pubescent to lanate, hairs white, to 0.8 mm near filament attachment, sutures denticulate, teeth to 0.2 mm; staminode 16–19 mm, included, 0.4–0.6 mm diam., glabrous; style 18–27 mm. Capsules 6–9 × 4–5 mm. 2n = 16, 32.
Varieties 3 (3 in the flora).
Penstemon heterophyllus apparently occurs only in California (see discussion under 209c. var. purdyi). The species includes three varieties concentrated in the Coast Ranges from Humboldt County south to San Bernardino and San Diego counties.
|1||Thyrse axes glabrous; stems glabrous, rarely retrorsely hairy; calyx lobes obovate to oblanceolate, rarely lanceolate.||Penstemon heterophyllus var. heterophyllus|
|1||Thyrse axes retrorsely hairy; stems retrorsely hairy; calyx lobes ovate to lanceolate.||> 2|
|2||Cauline leaves 15–45 × 0.5–4 mm, axillary fascicles present, sometimes absent.||Penstemon heterophyllus var. australis|
|2||Cauline leaves (25–)30–100 × 2–12 mm, axillary fascicles absent, rarely present.||Penstemon heterophyllus var. purdyi|