Penstemon sect. Spectabiles

Herbs, shrubs, or subshrubs. Stems glabrous, glaucous, sometimes not. Leaves basal and cauline, basals sometimes few (P. clevelandii, P. stephensii) or absent (P. clevelandii), or leaves essentially cauline (P. fruticiformis, P. incertus), opposite, leathery, sometimes not (P. pseudospectabilis, P. spectabilis, P. stephensii), glabrous, glaucous, sometimes not (P. clevelandii, P. spectabilis, P. stephensii); basal and proximal cauline petiolate; cauline sessile or short-petiolate, blade cordate, ovate, triangular-ovate, triangular, oblanceolate, triangular-lanceolate, lanceolate, ovate-oblong, or linear, margins entire or toothed. Thyrses interrupted, rarely continuous, cylindric or secund, axis glabrous or glandular-pubescent, cymes 2 per node; peduncles and pedicels spreading to ascending or erect. Flowers: calyx lobes: margins entire or erose, sometimes denticulate (P. spectabilis), ± scarious, sometimes herbaceous (P. pseudospectabilis), glabrous or glandular-pubescent; corolla white to pink, rose, red, magenta, yellow, lavender, blue, violet, or purple, bilaterally symmetric, bilabiate to strongly bilabiate, not personate, ventricose or ventricose-ampliate, sometimes tubular-funnelform or funnelform, glandular-pubescent externally, sometimes glabrous, glabrous or hairy internally abaxially, glandular-pubescent on both surfaces, or glandular-pubescent on both surfaces and hairy abaxially, throat gradually to abruptly inflated, constricted or not at orifice, rounded abaxially, sometimes 2-ridged; stamens included or longer pair reaching orifice or exserted, filaments glabrous or shorter pair glandular-puberulent proximally, pollen sacs opposite, rarely divergent (P. incertus), navicular to subexplanate or explanate, dehiscing completely, rarely incompletely (P. incertus), connective splitting, rarely not (P. incertus), sides glabrous, sutures smooth, rarely papillate or denticulate, teeth to 0.1 mm; staminode included or exserted, flattened distally, 0.2–1.1 mm diam., tip straight to recurved, rarely coiled, glabrous or distal 10–50% hairy, hairs to 4 mm, sometimes proximal 10–40% hairy, hairs glandular; style glabrous, rarely sparsely glandular-pubescent proximally. Capsules glabrous or sparsely glandular-pubescent distally. Seeds brown to dark brown or black, angled, rarely ± rounded, 1–4 mm.

Distribution

w United States, n Mexico.

Discussion

Species 16 (12 in the flora).

D. D. Keck (1937b) circumscribed sect. Peltanthera, a name that is illegitimate and superfluous, to include species from southwestern United States and northern Mexico with showy, white to pink, red, or purple, tubular to ventricose corollas and completely dehiscent, glabrous pollen sacs. His section encompasses species included here mostly in sect. Spectabiles and species treated here in sects. Gentianoides and Petiolati. Core species of sect. Spectabiles, those with ventricose corollas and treated by Keck in so-called subsect. Spectabiles (not validly published), were monophyletic in a molecular study (C. A. Wessinger et al. 2016) that included nine of the 12 species treated here in sect. Spectabiles. That study also provided support for inclusion of Penstemon alamosensis and P. parryi, species with tubular corollas and treated here in sect. Gentianoides, in sect. Spectabiles. However, broader taxon sampling is needed before definitive circumscription of sects. Gentianoides and Spectabiles is possible. Four species and one variety in sect. Spectabiles occur in Mexico: P. angelicus (I. M. Johnston) Moran, P. eximius D. D. Keck, P. rotundifolius A. Gray, P. spectabilis var. subinteger (D. D. Keck) C. C. Freeman, and P. vizcainensis Moran.

Selected References

Clokey, I. W. and D. D. Keck. 1939. Reconsideration of certain members of Penstemon subsection Spectabiles. Bull. S. Calif. Acad. Sci. 38: 8–13.

Keck, D. D. 1937b. Studies in Penstemon V. The section Peltanthera. Amer. Midl. Naturalist 18: 790–829.

Lower Taxa

Penstemon bicolor, Penstemon clevelandii, Penstemon clutei, Penstemon floridus, Penstemon fruticiformis, Penstemon grinnellii, Penstemon incertus, Penstemon palmeri, Penstemon pseudospectabilis, Penstemon rubicundus, Penstemon spectabilis, Penstemon stephensii

Key

1	Cauline leaf blade margins entire.	> 2
2	Corollas glabrous externally.	Penstemon fruticiformis
2	Corollas glandular-pubescent externally.	> 3
3	Corollas tubular-funnelform to slightly ventricose, red to reddish purple.	Penstemon clevelandii
3	Corollas ventricose-ampliate, purple, violet, blue, bluish lavender, lavender, or light pink.	> 4
4	Peduncles and pedicels glabrous; corolla tubes 6–8 mm, lengths 1–1.5 times calyx lobes.	Penstemon fruticiformis
4	Peduncles and pedicels glandular-pubescent; corolla tubes 7–11 mm, lengths 1.8–2 times calyx lobes.	Penstemon incertus
1	Cauline leaf blade margins serrate to dentate, rarely ± serrulate (at least proximals, distals sometimes entire).	> 5
5	Corollas tubular-funnelform or funnelform to slightly ventricose.	> 6
6	Calyx lobes 3.2–6 mm; corolla throats 5–8 mm diam.; staminodes glabrous or distal 1–6 mm pilose, hairs yellow, to 0.8 mm, proximal 1–2 mm sometimes glandular-puberulent.	Penstemon clevelandii
6	Calyx lobes 3–4.2(–5) mm; corolla throats 4–6 mm diam.; staminodes glabrous.	Penstemon stephensii
5	Corollas ventricose to ventricose-ampliate.	> 7
7	Corolla tube lengths 0.9–1.5 times calyx lobes.	> 8
8	Cauline leaves 2–8 mm wide, blades lanceolate to linear, sometimes oblanceolate.	Penstemon fruticiformis
8	Cauline leaves 4–45 mm wide, blades lanceolate to ovate-oblong, ovate, or triangular.	> 9
9	Cauline leaf blades lanceolate to ovate-oblong, bases tapered; staminodes 20–22 mm; styles 15–18 mm.	Penstemon grinnellii
9	Cauline leaf blades ovate to triangular, bases of distals auriculate-clasping or connate-perfoliate; staminodes 25–30 mm; styles 19–23 mm.	Penstemon palmeri
7	Corolla tube lengths 1.6–2.2 times calyx lobes.	> 10
10	Cauline leaves (1–)2.5–4(–6) mm wide, blades lanceolate to linear.	Penstemon incertus
10	Cauline leaves 5–76 mm wide, blades ovate to triangular or lanceolate.	> 11
11	Peduncles and pedicels spreading to ascending; pollen sacs navicular, sutures papillate or denticulate; corollas lavender, blue, pink, or purple.	Penstemon spectabilis
11	Peduncles and pedicels ascending to erect; pollen sacs explanate or navicular, sutures smooth; corollas pink to rose pink, lavender, purple, or light yellow.	> 12
12	Cauline leaf blades ovate to lanceolate; filaments glabrous.	> 13
13	Corollas 21–32 mm; staminodes included, glabrous.	Penstemon floridus
13	Corollas (27–)30–35 mm; staminodes exserted, distal 6–7 mm pilose.	Penstemon rubicundus
12	Cauline leaf blades ovate to triangular or lanceolate; filaments of shorter stamen pairs glandular-puberulent proximally.	> 14
14	Staminodes: distal 4–5 mm lanate, hairs to 2.8 mm; Arizona, California, Nevada.	Penstemon bicolor
14	Staminodes: glabrous or distal 1–4 mm sparsely to moderately lanate, hairs to 1 mm; Arizona, California, New Mexico, Utah.	> 15
15	Corollas glandular-pubescent internally, also usually moderately white-lanate internally abaxially, throats 9–12 mm diam.; Arizona.	Penstemon clutei
15	Corollas glandular-pubescent internally, throats 7–10 mm diam.; Arizona, California, New Mexico, Utah.	Penstemon pseudospectabilis