Flowers: pollen sacs navicular, navicular-sigmoid, saccate, or explanate, dehiscing completely or incompletely, connective splitting or not, sides glabrous or hairy, hairs not concealing surface, sutures smooth, papillate, or denticulate; staminode included to exserted, if included, length 3/4+ times corolla throat. Seeds angled or rounded, rarely angled-elongate, reniform, or disciform, wings absent.

Distribution

North America, Mexico, Central America (Guatemala).

Discussion

Species ca. 270 (229 in the flora).

Following the recommendation of A. D. Wolfe et al. (2006), subg. Penstemon is expanded here to include species of Penstemon not included in subg. Dasanthera. Molecular data indicate that some sections as usually circumscribed are paraphyletic. Absent a robust phylogeny for Penstemon, a morphology-based classification is followed here with minor adjustments. As circumscribed here, subg. Penstemon comprises 16 sections, 15 in the flora area.

Section Leptostemon Trautvetter includes 27 species from Mexico and Guatemala. Among its members are Penstemon campanulatus (Cavanilles) Willdenow, P. gentianoides (Kunth) Poiret, and P. hartwegii Bentham, three red- or purple-flowered species popular among European plant breeders in the nineteenth century and used in the development of European hybrid penstemons (R. Nold 1999; D. Lindgren and E. Wilde 2003).

Selected References

None.

Lower Taxa

Penstemon sect. Ambigui, Penstemon sect. Baccharifolii, Penstemon sect. Bridgesiani, Penstemon sect. Caespitosi, Penstemon sect. Chamaeleon, Penstemon sect. Coerulei, Penstemon sect. Cristati, Penstemon sect. Dissecti, Penstemon sect. Elmigera, Penstemon sect. Gentianoides, Penstemon sect. Glabri, Penstemon sect. Penstemon, Penstemon sect. Petiolati, Penstemon sect. Saccanthera, Penstemon sect. Spectabiles

Key

1	Cauline leaf blade margins deeply pinnatifid to nearly pinnatisect.	26b.8. Penstemon sect. Dissecti
1	Cauline leaf blade margins entire or toothed, rarely laciniate-pinnatifid.	> 2
2	Subshrubs or shrubs; staminodes glabrous; corollas pink, red, scarlet, or magenta, rarely lavender or violet.	> 3
3	Cauline leaf blades linear and pollen sacs explanate.	26b.1. Penstemon sect. Ambigui
3	Cauline leaf blades obovate, ovate, oblanceolate, lanceolate, elliptic, or linear; pollen sacs navicular, saccate, subexplanate, or explanate.	> 4
4	Pollen sacs subexplanate to explanate, opposite; corollas weakly ventricose; thyrses cylindric; leaves glaucous.	26b.13. Penstemon sect. Petiolati
4	Pollen sacs saccate or navicular, parallel or divergent; corollas salverform or funnelform; thyrses secund; leaves not glaucous.	> 5
5	Cauline leaf margins toothed or entire; corollas funnelform, glandular-pubescent internally abaxially and adaxially; cymes 1 per node; Texas.	26b.2. Penstemon sect. Baccharifolii
5	Cauline leaf margins entire; corollas salverform, hairy internally abaxially; cymes 2 per node; Arizona, California, Colorado, Nevada, New Mexico, Utah.	26b.3. Penstemon sect. Bridgesiani
2	Herbs, shrubs, or subshrubs; staminodes hairy distally or glabrous; corollas usually white, lavender, lilac, blue, violet, purple, ochroleucous, yellow, orange, or crimson, if pink, red, scarlet, or magenta, herbs and/or staminodes hairy, or both.	> 6
6	Pollen sacs saccate, dehiscing incompletely, distal 1/5–2/3 indehiscent, connectives splitting, rarely not.	> 7
7	Pollen sac sutures papillate; herbs.	26b.12. Penstemon sect. Penstemon
7	Pollen sac sutures denticulate; herbs or subshrubs.	> 8
8	Herbs; pollen sac sides glabrous; staminodes glabrous, tips recurved; cauline leaf blade margins entire; thyrses interrupted.	26b.5. Penstemon sect. Chamaeleon
8	Herbs or subshrubs; pollen sac sides glabrous or hairy; staminodes glabrous or hairy distally, tips straight; cauline leaf blade margins entire or toothed, rarely laciniate-pinnatifid; thyrses interrupted or continuous.	26b.14. Penstemon sect. Saccanthera
6	Pollen sacs navicular, navicular-sigmoid, sigmoid, subexplanate, or explanate, dehiscing completely, if incompletely proximal 1/5–1/2 indehiscent and/or connectives not splitting.	> 9
9	Pollen sacs dehiscing incompletely, proximal 1/5–1/2 indehiscent and/or connectives not splitting.	> 10
10	Corollas red to scarlet or orange, rarely yellow, glabrous externally.	26b.9. Penstemon sect. Elmigera
10	Corollas white to pink, lavender, lilac, blue, violet, or purple, glandular-pubescent or glabrous externally, if corollas reddish pink or rose red, glandular-pubescent externally.	> 11
11	Pollen sacs: connectives not splitting, sutures papillate, sides glabrous; corollas tubular-funnelform.	26b.7. Penstemon sect. Cristati
11	Pollen sacs: proximal 1/5–1/3 indehiscent and/or connectives not splitting, sutures denticulate, sometimes papillate or smooth, sides glabrous or hairy; corollas funnelform, ventricose, or ventricose-ampliate.	26b.11. Penstemon sect. Glabri
9	Pollen sacs dehiscing completely (rarely connectives not splitting in P. incertus).	> 12
12	Staminodes glabrous; pollen sacs parallel to divergent, sutures denticulate, teeth to 0.2–0.3 mm.	26b.5. Penstemon sect. Chamaeleon
12	Staminodes hairy distally, sometimes glabrous; pollen sacs opposite or divergent, rarely parallel, sutures smooth, papillate, or denticulate, teeth to 0.1–0.2 mm.	> 13
13	Subshrubs; leaves cauline, rarely basal and cauline, blade margins entire; stems not glaucous; corollas 2-ridged abaxially.	26b.4. Penstemon sect. Caespitosi
13	Herbs, shrubs, or subshrubs; leaves basal and cauline, sometimes basal few or absent, blade margins entire or toothed, if shrubs or subshrubs, leaves basal and cauline or leaf blade margins toothed or stems glaucous; corollas rounded to 2-ridged abaxially.	> 14
14	Stems and/or leaves and/or thyrse axes hairy; leaf blades not (or rarely) glaucous, not (or rarely) leathery.	> 15
15	Corollas glabrous externally, ventricose or ventricose-ampliate.	26b.11. Penstemon sect. Glabri
15	Corollas glandular-pubescent externally, if glabrous then tubular, tubular-funnelform, or funnelform.	> 16
16	Corolla throats rounded abaxially, sometimes slightly 2-ridged; staminodes: distal (40–)50–100% hairy, hairs to 4 mm, exserted, sometimes reaching orifice or included, tips straight to recurved or coiled; seeds 1.4–4.8 mm, brown, dark brown, or black.	26b.7. Penstemon sect. Cristati
16	Corolla throats slightly to prominently 2-ridged abaxially, rarely rounded; staminodes: distal 5–60(–90)% hairy, hairs to 3 mm, sometimes glabrous, included or reaching orifice, sometimes exserted, tips straight to recurved; seeds 0.4–2(–3.5) mm, tan, brown, gray, or black.	26b.12. Penstemon sect. Penstemon
14	Stems, leaves, and thyrse axes glabrous, rarely scabrous; leaf blades glaucous, rarely not, leathery, rarely not.	> 17
17	Shrubs or subshrubs; stamen filaments: shorter pair glandular-puberulent proximally.	26b.15. Penstemon sect. Spectabiles
17	Herbs; stamen filaments glabrous.	> 18
18	Leaf blade margins toothed.	26b.15. Penstemon sect. Spectabiles
18	Leaf blade margins entire (rarely remotely and obscurely toothed in P. parryi).	> 19
19	Stamens exserted; corollas red, 32–36 mm.	26b.6. Penstemon sect. Coerulei
19	Stamens included or longer pair reaching orifice, rarely exserted; corollas lavender to blue, violet, purple, white, pink, lilac, red, scarlet, crimson, magenta, orange, yellow, or ochroleucous, 6–33 mm.	> 20
20	Basal and proximal cauline leaf blades linear, 0.5–1.5 mm wide.	26b.7. Penstemon sect. Cristati
20	Leaf blades ovate, obovate, lanceolate, oblanceolate, spatulate, trullate, oblong, or elliptic, rarely linear, 1–70 mm wide.	> 21
21	Pollen sacs 0.3–1.2 mm, opposite; corollas 7–22 mm, throats 2-ridged abaxially, sometimes rounded.	26b.12. Penstemon sect. Penstemon
21	Pollen sacs 0.6–3 mm, opposite, divergent, or parallel; corollas 10–48 mm, throats rounded abaxially, rarely slightly 2-ridged.	> 22
22	Pollens sacs navicular; corollas glabrous externally, rarely obscurely glandular (P. carnosus).	26b.6. Penstemon sect. Coerulei
22	Pollen sacs explanate, sometimes navicular; corollas glandular-pubescent externally, if glabrous staminode papillate distally, papillae to 0.2 mm.	26b.10. Penstemon sect. Gentianoides