Stems prostrate, only tip ascending, 2–8(–10) cm, not cinereous, retrorsely hairy, hairs pointed. Leaves not leathery, not cinereous, retrorsely hairy, hairs pointed; cauline 3–20 pairs, petiolate, 2.5–14(–21) × 1–4 mm, blade obovate to spatulate, oblanceolate, or linear, base tapered, apex rounded to acute or mucronate. Thyrses continuous, cylindric to secund, 0.5–3 cm, axis retrorsely hairy to retrorsely cinereous, hairs pointed, sometimes also glandular-pubescent, verticillasters 1–5, cymes 1–3-flowered, 1 per node; proximal bracts linear, 2.8–13(–17) × 0.7–3 mm; peduncles and pedicels ascending to erect, retrorsely hairy to retrorsely cinereous, hairs pointed, and glandular-pubescent. Flowers: calyx lobes lanceolate to linear, 4–6.5(–8.5) × 1–1.5(–1.9) mm, herbaceous- or narrowly scarious-margined, retrorsely hairy, hairs pointed, and sparsely glandular-pubescent; corolla blue to purplish lavender or lavender, lined internally abaxially with reddish violet nectar guides, funnelform, 10–17(–21) mm, yellow-villous internally abaxially, tube 5–6 mm, throat gradually inflated, 4.5–6 mm diam., 2-ridged abaxially; stamens: longer pair reaching orifice or exserted, filaments glabrous, pollen sacs opposite, navicular to explanate, 0.6–1.2 mm, sutures papillate; staminode 9–12 mm, reaching orifice, flattened distally, 0.3–0.5 mm diam., tip straight to recurved, distal 7–9 mm densely pilose, hairs golden yellow, to 1 mm; style 13–15 mm. Capsules 3.5–5 × 3–4 mm.
Ariz., Colo., Utah, Wyo.
Varieties 3 (3 in the flora).
The varieties of Penstemon caespitosus are weakly differentiated and largely allopatric.
|1||Pollen sacs 0.9–1.2 mm; leaf blades oblanceolate; Arizona, Utah.||Penstemon caespitosus var. desertipicti|
|1||Pollen sacs 0.6–0.9 mm; leaf blades obovate, spatulate, oblanceolate, or linear; Colorado, Utah, Wyoming.||> 2|
|2||Leaf blades oblanceolate to linear; pollen sacs explanate, 0.6–0.8 mm; Colorado, Utah, Wyoming.||Penstemon caespitosus var. caespitosus|
|2||Leaf blades obovate or spatulate; pollen sacs navicular to subexplanate, 0.8–0.9 mm; Colorado, Utah.||Penstemon caespitosus var. perbrevis|