Penstemon diphyllus


Mem. New York Bot. Gard. 1: 349. 1900. (as Pentstemon)

Common names: Two-leaf beardtongue
Treatment appears in FNA Volume 17. Treatment on page 232. Mentioned on page 229, 233.

Subshrubs. Stems ascending to erect, (10–)20–80 cm, retrorsely hairy, not glaucous. Leaves cauline, opposite, sometimes alternate, glabrous, not glaucous; cauline (4–)7–10 pairs, sessile or proximals short-petiolate, 20–80 × 5–17 mm, blade elliptic to lanceolate or oblanceolate, base tapered, margins irregularly dentate or serrate, apex acute. Thyrses interrupted, cylindric, 3–25(–50) cm, axis glandular-pubescent, verticillasters 4–10, cymes 1–11(–18)-flowered, 1 or 2 per node; proximal bracts lanceolate, rarely ovate, 9–45 × 2–16 mm; peduncles and pedicels spreading to ascending, glandular-pubescent. Flowers: calyx lobes lanceolate, (2–)3–5.2 × 0.9–1.3 mm, glandular-pubescent; corolla bluish lavender to violet or purple, with reddish purple nectar guides, funnelform, 13–19 mm, glandular-pubescent externally, glabrous internally or sparsely white-lanate abaxially, tube 5–6 mm, throat gradually inflated, 5–6 mm diam., rounded abaxially; stamens included, filaments glabrous or sparsely white-pubescent distally, pollen sacs parallel, 0.9–1.3 mm, distal 1/2 indehiscent, sides glabrous, sutures denticulate, teeth to 0.1 mm; staminode 9–11 mm, reaching orifice or barely exserted, 0.4–0.5 mm diam., distal 1–4 mm sparsely to moderately lanate, hairs white or yellowish, to 1.5 mm; style 8–12 mm. Capsules 4–6 × 2.8–4.5 mm.

Phenology: Flowering Jun–Aug(–Sep).
Habitat: Talus slopes, cliffs, rocky banks.
Elevation: 1000–2300 m.


Penstemon diphyllus occurs in northeastern Idaho, western Montana, and southeastern Washington (Whitman County).

Selected References


Lower Taxa