Penstemon sect. Coerulei

Herbs. Stems glabrous, sometimes scabrous, glaucous. Leaves basal and cauline, sometimes basal absent or reduced, opposite, leathery, glabrous, rarely scabrous, glaucous; basal and proximal cauline petiolate, sometimes short-petiolate (P. immanifestus, P. lentus); cauline sessile, sometimes short-petiolate, blade obovate, ovate, spatulate, trullate, oblanceolate, lanceolate, oblong, elliptic, linear, or orbiculate, margins entire. Thyrses continuous or interrupted, cylindric, sometimes secund, axis glabrous, rarely scabrous or glutinous, cymes 2 per node; peduncles and pedicels ascending to erect. Flowers: calyx lobes: margins entire or erose, herbaceous or ± scarious, glabrous, rarely scabrous, glandular, glandular-pubescent, or glutinous; corolla lavender to blue, violet, purple, or pink, rarely white or red, bilaterally symmetric, rarely nearly radially symmetric (P. cyathophorus), weakly, rarely strongly, bilabiate, not personate, tubular-funnelform, funnelform, or weakly ventricose, rarely tubular-salverform or weakly ampliate, glabrous externally, rarely obscurely glandular, glabrous or hairy internally abaxially, throat slightly to abruptly inflated, not constricted at orifice, rounded abaxially, rarely slightly 2-ridged; stamens included to exserted, filaments glabrous, pollen sacs opposite, rarely divergent or parallel, navicular, rarely explanate (P. murrayanus), dehiscing completely, connective splitting, sides glabrous, sutures papillate, sometimes smooth; staminode included to exserted, flattened distally, (0.2–)0.4–3 mm diam., tip recurved, rarely coiled or straight, distal 10–50(–70)% hairy, hairs to 2.5 mm, rarely glabrous; style glabrous. Capsules glabrous. Seeds brown or dark brown, angled, angled-elongate, or disciform, 1.8–5.4 mm.

Distribution

North America, n Mexico.

Discussion

Species 20 (20 in the flora).

D. D. Keck (1951) proposed the section name Anularius for sect. Coerulei, believing that the name of Pennell was invalid. N. H. Holmgren (1979b) concluded that the section names of Pennell are valid and that sect. Anularius Keck is invalid; the new combinations by Keck in that publication lacked descriptions.

Members of sect. Coerulei usually are recognized by their mostly glabrous, glaucous, and fleshy herbage, their blue or pink corollas that are glabrous, rarely obscurely glandular, externally, and their relatively broad and heavily bearded staminodes. Penstemon murrayanus has red corollas and glabrous staminodes. Members of sect. Coerulei mostly occur on well-drained, sandy soils. Molecular data (C. A. Wessinger et al. 2016) support the monophyly of the section.

Selected References

None.

Lower Taxa

Penstemon acuminatus, Penstemon angustifolius, Penstemon arenicola, Penstemon bracteatus, Penstemon buckleyi, Penstemon carnosus, Penstemon cyathophorus, Penstemon fendleri, Penstemon flowersii, Penstemon grandiflorus, Penstemon harringtonii, Penstemon haydenii, Penstemon immanifestus, Penstemon lentus, Penstemon mucronatus, Penstemon murrayanus, Penstemon nitidus, Penstemon osterhoutii, Penstemon pachyphyllus, Penstemon secundiflorus

Key

1	Corollas red; staminodes glabrous; pollen sacs explanate.	Penstemon murrayanus
1	Corollas lavender to blue, violet, purple, or pink, rarely white; staminodes hairy; pollen sacs navicular.	> 2
2	Pollen sacs parallel or divergent; stamens: 2 or 4 prominently exserted; corollas without nectar guides.	> 3
3	Stamens: 4 exserted; pollen sacs 1.2–1.5 mm; corollas 11–14 mm.	Penstemon cyathophorus
3	Stamens: 2 exserted; pollen sacs 2–3 mm; corollas 17–24 mm.	Penstemon harringtonii
2	Pollen sacs opposite or divergent; stamens included or longer pair reaching orifice to slightly exserted; corollas usually with nectar guides.	> 4
4	Corollas 21–48 mm, ampliate, glabrous internally, throats abruptly inflated.	> 5
5	Corollas 35–48 mm; cauline leaf blades spatulate to orbiculate.	Penstemon grandiflorus
5	Corollas 21–28 mm; cauline leaf blades lanceolate to linear.	Penstemon haydenii
4	Corollas 10–25(–28) mm, tubular-funnelform, tubular-salverform, funnelform, or ventricose, white-villous internally abaxially or glabrous, throats not abruptly inflated.	> 6
6	Corollas tubular-salverform; thyrses interrupted.	Penstemon fendleri
6	Corollas tubular-funnelform, funnelform, or ventricose; thyrses continuous or interrupted.	> 7
7	Stems 3–10(–15) cm; cauline leaf pairs 1–3; thyrses 1–6 cm; verticillasters 1–5(or 6).	Penstemon bracteatus
7	Stems (4–)7–77(–82) cm; cauline leaf pairs 1–8(or 9); thyrses (2–)3–37(–57) cm; verticillasters (2 or)3–20(–35).	> 8
8	Thyrses secund.	> 9
9	Cauline leaves 2–4 pairs; staminodes 8–9 mm, distal 3–4 mm sparsely to densely villous, hairs yellowish, to 1 mm; Arizona, Colorado, New Mexico, Utah.	Penstemon lentus
9	Cauline leaves 4–6 pairs; staminodes 10–13 mm, distal 4–6 mm densely villous, hairs golden yellow, to 2 mm; Colorado, New Mexico, Wyoming.	Penstemon secundiflorus
8	Thyrses cylindric.	> 10
10	Staminodes 2–3 mm diam.; corollas with nectar guides, sparsely to moderately white-villous internally abaxially, rarely glabrous.	Penstemon osterhoutii
10	Staminodes (0.2–)0.4–2 mm diam.; corollas with or without nectar guides, glabrous or sparsely white-villous internally abaxially.	> 11
11	Corollas pink or white.	> 12
12	Corollas white.	Penstemon lentus
12	Corollas pink.	> 13
13	Leaves: basal usually reduced or absent; corollas glabrous internally; staminodes: distal 0.5–1.5 mm lanulose, hairs to 0.6 mm.	Penstemon flowersii
13	Leaves: basal not reduced; corollas sparsely white-hairy internally abaxially or glabrous; staminodes: distal 2–6 mm villous, hairs to 1 mm.	> 14
14	Cauline leaf apices acute to acuminate; corollas tubular-funnelform; calyx lobes ovate to lanceolate, 4–8 × 1–2.5 mm.	Penstemon angustifolius
14	Cauline leaf apices obtuse to acute; corollas funnelform to ventricose; calyx lobes ovate, 5–8(–12) × 2–3.5 mm.	Penstemon immanifestus
11	Corollas blue, pinkish blue, lavender-blue, lavender, violet, or purple, rarely some individuals with corollas pink.	> 15
15	Cauline leaf blades ovate to orbiculate; corollas with nectar guides, villous internally abaxially.	Penstemon mucronatus
15	Cauline leaf blades elliptic to ovate, obovate, lanceolate, oblanceolate, or linear; corollas with or without nectar guides, glabrous or villous internally abaxially.	> 16
16	Stems decumbent to ascending, (4–)7–18(–30) cm; thyrses continuous; proximal bracts oblanceolate to lanceolate; corollas (10–)12–15 mm; pollen sacs 0.7–0.8 mm.	Penstemon arenicola
16	Stems ascending to erect, (5–)9–60(–82) cm; thyrses interrupted or continuous; proximal bracts orbiculate to ovate, lanceolate, oblong, or linear; corollas 10–22 mm; pollen sacs 0.7–1.6 mm.	> 17
17	Proximal bracts orbiculate to ovate; corollas lavender to bluish lavender or pinkish blue, glabrous internally; capsules 12–18(–20) mm.	Penstemon buckleyi
17	Proximal bracts ovate to oblong, lanceolate, or linear, rarely orbiculate; corollas blue, pinkish blue, bluish lavender, violet, or purple, hairy internally abaxially or glabrous; capsules 7–15 mm.	> 18
18	Corollas obscurely glandular externally or glabrous; cauline leaves 1–3 pairs; thyrses 3–15 cm, continuous, sometimes interrupted.	Penstemon carnosus
18	Corollas glabrous externally; cauline leaves 2–8 pairs; thyrses (2–)5–30(–37) cm, continuous or interrupted.	> 19
19	Staminodes 1–2 mm diam., distal 6–8 mm villous, hairs to 2.5 mm.	Penstemon pachyphyllus
19	Staminodes (0.2–)0.5–1.5 mm diam., distal 1.5–7 mm pilose to villous, hairs to 1.5 mm.	> 20
20	Cauline leaf blades: apices obtuse to acute, sometimes rounded or mucronate; peduncles to 12–28 mm; corolla throats 5–8 mm diam.	> 21
21	Cymes 1–3(or 4)-flowered; cauline leaves sessile; seeds 3.5–5 mm.	Penstemon lentus
21	Cymes (1 or)2–6-flowered; cauline leaves short-petiolate or sessile; seeds 2–4 mm.	> 22
22	Corollas bluish lavender to lavender, 15–22 mm; peduncles to 12 mm; calyx lobes ovate, 5–8(–12) mm, apices acuminate; staminodes: distal 2–5 mm densely villous, hairs yellowish, brownish, or orangish, to 1 mm.	Penstemon immanifestus
22	Corollas blue to violet, sometimes lavender, 12–20 mm; peduncles to 26 mm; calyx lobes ovate to lanceolate, (2.5–)4–7 mm, apices acute to acuminate or caudate; staminodes: distal 4–8 mm densely villous, hairs yellow to golden yellow, to 2.5 mm.	Penstemon pachyphyllus
20	Cauline leaf blades: apices acute to acuminate, sometimes mucronate (P. nitidus); peduncles to 3–4 mm; corolla throats 4–6 mm diam.	> 23
23	Cymes 2–5-flowered, verticillasters (2–)4–10; corolla tubes 4–6 mm; stems glabrous.	Penstemon nitidus
23	Cymes (2–)4–8(–12)-flowered, verticillasters (3–)5–15(–26); corolla tubes 5–9 mm; stems glabrous or scabrous.	> 24
24	Staminodes: distal 1.5–3.5 mm densely pilose, hairs to 0.6 mm; calyx lobes lanceolate, (3.2–)4.5–10 × 1.2–3.2(–3.8) mm; pollen sacs 0.7–1.3(–1.5) mm; Idaho, Nevada, Oregon, Washington.	Penstemon acuminatus
24	Staminodes: distal 4–6 mm sparsely villous, hairs to 1 mm; calyx lobes ovate to lanceolate, 4–8 × 1–2.5 mm; pollen sacs (0.9–)1.1–1.5 mm; Arizona, Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Utah, Wyoming.	Penstemon angustifolius