Penstemon linarioides

A. Gray

in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 112. 1859. (as Pentstemon)

Common names: Toad-flax beardtongue
Treatment appears in FNA Volume 17. Treatment on page 103. Mentioned on page 99, 104.

Stems ascending to erect, 8–50 cm, retrorsely hairy, hairs pointed or white, scalelike. Leaves not leathery, glabrous, glabrate, or sparsely to densely retrorsely hairy, hairs pointed, sometimes appressed, white, scalelike; cauline 6–12(–20) pairs, petiolate or sessile, 4–26 × 0.5–3.5 mm, blade oblanceolate to lanceolate or linear, base tapered to truncate, apex mucronate. Thyrses continuous or interrupted, ± secund, 3–17 cm, axis glandular-pubescent, verticillasters 3–9(–12), cymes 1 or 2(or 3)-flowered, 1(or 2) per node; proximal bracts lanceolate to linear, 6–25 × 0.7–1 mm; peduncles and pedicels ascending to erect, retrorsely hairy, hairs pointed, and sparsely glandular-pubescent. Flowers: calyx lobes ovate, rarely lanceolate, 4–7(–9) × 2–3 mm, broadly scarious-margined, apex acute to acuminate, glandular-pubescent, hairs pointed; corolla blue or lavender, lined internally abaxially with reddish purple nectar guides, ventricose-ampliate, 16–20 mm, moderately white- or yellowish villous internally abaxially, tube 5–6 mm, throat abruptly inflated, 5.5–8 mm diam., slightly 2-ridged abaxially; stamens: longer pair reaching orifice or slightly exserted, filaments glabrous, pollen sacs opposite, navicular, 0.9–1.3 mm, sutures papillate; staminode 6–8 mm, exserted, flattened distally, 0.3–0.5 mm diam., tip straight to recurved, distal 1–5 mm densely pilose, hairs yellow or golden yellow, to 1.2 mm, rest of distal 1–7 mm glabrous or sparsely to moderately pilose; style 10–11 mm. Capsules 5–9 × 3.5–5 mm.


Ariz., Colo., N.Mex., Nev., Utah


Varieties 4 (4 in the flora).

Penstemon linarioides is widespread and highly variable. D. D. Keck (1937) recognized seven subspecies on the basis of habit, pubescence, leaf shape, and staminode bearding. Some of the variation on which those subspecies are based appears to be clinal or too variable within or among regional populations to be of taxonomic value.

Selected References



1 Leaves glabrous, glabrate, retrorsely hairy, or pubescent, hairs pointed. Penstemon linarioides var. sileri
1 Leaves sparsely to densely retrorsely hairy, hairs appressed, white, scalelike. > 2
2 Cauline leaf blades oblanceolate, distals sometimes lanceolate, 1.5–3.5 mm wide. Penstemon linarioides var. maguirei
2 Cauline leaf blades oblanceolate to linear, 0.5–2 mm wide. > 3
3 Staminodes: distal 3–5 mm densely pilose, hairs golden yellow or yellow, to 1 mm, rest of distal 1–4 mm sparsely to moderately pilose. Penstemon linarioides var. linarioides
3 Staminodes: distal 1 mm densely pilose, hairs yellow, to 0.8 mm, rest of distal 3–4 mm glabrous or sparsely pilose (with much shorter hairs). Penstemon linarioides var. coloradoensis