Herbs. Stems glabrous, retrorsely hairy, canescent, glandular, or glandular-pubescent, rarely glutinous, glaucous or not. Leaves basal and cauline, sometimes basal absent or reduced, opposite, leathery or not, glabrous, glabrescent, scabrous, puberulent, retrorsely hairy, or glandular-pubescent, glaucous or not; basal and proximal cauline petiolate, sometimes short-petiolate (P. gibbensii, P. idahoensis); cauline sessile or petiolate, blade obovate, ovate, spatulate, oblanceolate, elliptic-lanceolate, lanceolate, elliptic, oblong, or linear, margins entire. Thyrses continuous or interrupted, cylindric, subsecund, or secund, axis glabrous, glandular-pubescent, puberulent, or retrorsely hairy, rarely glandular, cymes 1 or 2 per node; peduncles and pedicels ascending or erect, sometimes spreading (P. comarrhenus, P. cyananthus, P. nudiflorus). Flowers: calyx lobes: margins erose or entire, rarely lacerate (P. hallii), ± scarious, glabrous or glandular-pubescent, sometimes glandular, glutinous, or puberulent; corolla white to pink, lavender, blue, violet, or purple, bilaterally symmetric, weakly bilabiate to strongly bilabiate, not personate, funnelform, ventricose, or ventricose-ampliate, glabrous or glandular-pubescent externally, glabrous or hairy internally abaxially, rarely glandular-pubescent internally abaxially or adaxially, throat gradually to abruptly inflated, slightly constricted or not at orifice, rounded to 2-ridged abaxially; stamens included or longer pair reaching orifice or exserted, filaments glabrous, pollen sacs divergent to opposite, navicular, navicular-sigmoid, or sigmoid, rarely subexplanate, dehiscing incompletely proximal 1/5–1/3 indehiscent, rarely completely, connective splitting or not, sides glabrous, papillate, or hairy, sutures denticulate, teeth to 0.1–0.2 mm, sometimes papillate or smooth; staminode included to exserted, flattened distally, 0.2–1.3 mm diam., tip straight to recurved, distal 5–60(–90)% hairy or papillate, hairs or papillae to 1.5 mm, rarely glabrous; style glabrous. Capsules glabrous. Seeds tan to brown or dark brown, angled to angled-elongate, 0.9–4 mm.

Distribution

w United States, n Mexico.

Discussion

Species 44 (43 in the flora).

Pollen sacs dehiscing from their distal ends proximally and connectives usually not splitting has traditionally been used as a synapomorphy for subg. Habroanthus (F. S. Crosswhite 1967). Within subg. Habroanthus, species with blue or violet and tubular or ventricose corollas have been included in sect. Glabri; species with red and tubular corollas have been placed in sect. Elmigera. Molecular studies (A. D. Wolfe et al. 2006; C. A. Wessinger et al. 2016) revealed that the four red-flowered species of sect. Elmigera in the flora area are closely related to blue-flowered species of sect. Glabri. Penstemon galloensis G. L. Nesom, known from Nuevo León, Mexico, is the only member of sect. Glabri occurring strictly outside the flora area.

Selected References

Crosswhite, F. S. 1967. Revision of Penstemon section Habroanthus (Scrophulariaceae) I: Conspectus. Amer. Midl. Naturalist 77: 1–11.

Crosswhite, F. S. 1967b. Revision of Penstemon section Habroanthus (Scrophulariaceae) II: Series Speciosi. Amer. Midl. Naturalist 77: 12–27.

Crosswhite, F. S. 1967c. Revision of Penstemon section Habroanthus (Scrophulariaceae) III: Series Virgati. Amer. Midl. Naturalist 77: 28–41.

Moorman, M. L. 1982. Systematic Revision of Penstemon subglaber, P. saxosorum, and P. mensarum. M.S. thesis. University of Wyoming.

Lower Taxa

Penstemon absarokensis, Penstemon ammophilus, Penstemon caryi, Penstemon comarrhenus, Penstemon compactus, Penstemon cyananthus, Penstemon cyaneus, Penstemon cyanocaulis, Penstemon deaveri, Penstemon debilis, Penstemon fremontii, Penstemon gibbensii, Penstemon glaber, Penstemon hallii, Penstemon idahoensis, Penstemon laevis, Penstemon leiophyllus, Penstemon lemhiensis, Penstemon longiflorus, Penstemon mensarum, Penstemon moriahensis, Penstemon navajoa, Penstemon neomexicanus, Penstemon nudiflorus, Penstemon pahutensis, Penstemon parvus, Penstemon payettensis, Penstemon paysoniorum, Penstemon penlandii, Penstemon pennellianus, Penstemon perpulcher, Penstemon pseudoputus, Penstemon putus, Penstemon saxosorum, Penstemon scariosus, Penstemon speciosus, Penstemon strictiformis, Penstemon strictus, Penstemon subglaber, Penstemon tidestromii, Penstemon uintahensis, Penstemon virgatus, Penstemon wardii

Key

1	Pollen sac sides glabrous.	> 2
2	Corollas glandular-pubescent externally.	> 3
3	Stems glabrous; leaves glabrous.	Penstemon leiophyllus
3	Stems retrorsely hairy or puberulent to pubescent; leaves retrorsely hairy.	> 4
4	Corollas 13–20 mm; pollen sacs 1–1.4 mm, navicular; styles 11–15 mm.	Penstemon parvus
4	Corollas 24–30 mm; pollen sacs 2–2.5 mm, sigmoid; styles 20–24 mm.	Penstemon wardii
2	Corollas glabrous externally, rarely glutinous and covered with sand.	> 5
5	Stems glutinous and covered with sand, usually ± fistulose.	Penstemon ammophilus
5	Stems glabrous or retrorsely hairy, puberulent, pubescent, canescent, or glandular-pubescent, not glutinous and covered with sand, not fistulose.	> 6
6	Basal and proximal cauline leaf blades linear.	> 7
7	Stems retrorsely hairy; corollas glabrous internally.	Penstemon pseudoputus
7	Stems glabrous; corollas sparsely white-lanate internally abaxially.	Penstemon putus
6	Basal and proximal cauline leaf blades ovate to elliptic, obovate, oblanceolate, lanceolate, or spatulate, rarely linear (P. virgatus).	> 8
8	Stems glaucous; thyrses interrupted; peduncles and pedicels spreading to ascending; pollen sacs dehiscing completely.	Penstemon nudiflorus
8	Stems slightly or not glaucous; thyrses continuous or interrupted; peduncles and pedicels ascending to erect; pollen sacs dehiscing incompletely or completely.	> 9
9	Thyrse axes glandular-pubescent.	> 10
10	Corollas 14–25 mm; pollen sacs navicular to subexplanate, 1.2–1.4 mm, dehiscing completely.	Penstemon hallii
10	Corollas 25–35 mm; pollen sacs sigmoid, (1.8–)2–3 mm, dehiscing incompletely.	Penstemon speciosus
9	Thyrse axes glabrous or retrorsely hairy.	> 11
11	Pollen sacs dehiscing incompletely, proximal 1/5–1/3 indehiscent, connectives not splitting.	> 12
12	Calyx lobes (4–)4.5–11(–13.5) mm; pollen sacs sigmoid, (1.8–)2–3 mm.	> 13
13	Stems glabrous; pollen sacs 2–2.5 mm, sides glabrous; staminodes: distal 5–7 mm ± pilose, hairs yellow, to 1 mm; capsules 8–10 mm.	Penstemon laevis
13	Stems glabrous or retrorsely hairy; pollen sacs (1.8–)2–3 mm, sides glabrous or sparsely hispidulous; staminodes glabrous or distal 1–7 mm sparsely pilose, hairs yellow to yellowish orange, to 0.8 mm; capsules 10–16 mm.	Penstemon speciosus
12	Calyx lobes 2.5–5 mm; pollen sacs navicular, navicular-sigmoid, or sigmoid, 1.2–2.2 mm.	> 14
14	Staminodes glabrous; pollen sac sides lanate, rarely glabrous.	Penstemon navajoa
14	Staminodes pilose distally; pollen sac sides glabrous.	> 15
15	Corollas sparsely yellow- or white-villous internally abaxially; stems glabrous; pollen sacs sigmoid, 1.6–2.2 mm.	Penstemon pahutensis
15	Corollas glabrous internally; stems glabrous or retrorsely hairy; pollen sacs navicular-sigmoid or navicular, 1.3–1.7 mm.	> 16
16	Stems glabrous or retrorsely hairy; calyx lobes: margins broadly scarious, apices rounded to acute or mucronate; Idaho, Oregon.	Penstemon perpulcher
16	Stems retrorsely hairy; calyx lobes: margins narrowly scarious, apices obtuse, sometimes acute to cuspidate; Utah.	Penstemon tidestromii
11	Pollen sacs dehiscing completely or connectives not splitting.	> 17
17	Staminodes pilose to lanate distally.	> 18
18	Pollen sacs 1.2–1.5 mm, sutures smooth or papillate; staminodes: distal 0.5–2 mm sparsely to moderately pilose; styles 10–14 mm.	Penstemon deaveri
18	Pollen sacs 1.2–2.5(–2.8) mm, sutures denticulate; staminodes: distal 1–8 mm pilose or lanate; styles 11–20 mm.	> 19
19	Corollas 22–48 mm, glabrous or sparsely to moderately white-lanate internally abaxially.	Penstemon glaber
19	Corollas 13–22 mm, glabrous internally.	> 20
20	Stems glabrous.	Penstemon payettensis
20	Stems retrorsely hairy.	Penstemon tidestromii
17	Staminodes glabrous.	> 21
21	Cauline leaves 1–5 mm wide; pollen sac sides lanate, hairs to 0.9 mm, rarely glabrous; stems glabrous.	Penstemon navajoa
21	Cauline leaves 3–35(–43) mm wide; pollen sac sides glabrous or sparsely to moderately hirsute, hairs to 0.5 mm; stems glabrous or puberulent to pubescent.	> 22
22	Pollen sac sutures denticulate; cauline leaves (6–)22–35(–43) mm wide.	Penstemon glaber
22	Pollen sac sutures smooth or papillate; cauline leaves 3–17 mm wide.	> 23
23	Stems glabrous; corollas sparsely to densely white-villous internally abaxially; New Mexico.	Penstemon neomexicanus
23	Stems glabrous or puberulent; corollas sparsely white-villous internally abaxially, rarely glabrous; Arizona, Colorado, New Mexico, Wyoming.	Penstemon virgatus
1	Pollen sac sides hairy.	> 24
24	Corollas ± glandular-pubescent or glandular externally.	> 25
25	Pollen sacs: proximal 1/5–1/4 indehiscent.	> 26
26	Corollas 18–33 mm, throats 6–11 mm diam.; pollen sacs (1.3–)1.5–2.4 mm; styles 12–22 mm; stems glabrous.	Penstemon scariosus
26	Corollas 14–18(–20) mm, throats 5–7 mm diam.; pollen sacs 1–1.7 mm; styles 9–16 mm; stems puberulent, pubescent, retrorsely pubescent, or glabrous.	> 27
27	Thyrse axes glabrous; stems glabrous or ± puberulent proximally.	Penstemon cyanocaulis
27	Thyrse axes glandular-pubescent; stems pubescent to retrorsely hairy, sometimes glabrous proximally, glandular-pubescent distally.	Penstemon gibbensii
25	Pollen sacs: connectives not splitting.	> 28
28	Stems 5–15(–24) cm; corollas without nectar guides.	Penstemon uintahensis
28	Stems (10–)18–90(–130) cm; corollas with violet or reddish purple nectar guides.	> 29
29	Staminodes: distal 7–9 mm sparsely to moderately villous; styles 9–11 mm.	Penstemon mensarum
29	Staminodes: distal 2–5 mm sparsely villous; styles 14–18 mm.	> 30
30	Stems glabrous; corollas glabrous or ± glandular-pubescent internally abaxially; Colorado, Wyoming.	Penstemon saxosorum
30	Stems glabrous proximally, usually sparsely glandular distally; corollas glabrous internally; Idaho, Utah, Wyoming.	Penstemon subglaber
24	Corollas glabrous externally.	> 31
31	Stems glutinous, usually covered with sand.	> 32
32	Corollas 20–28 mm; styles 17–20 mm; pollen sacs 2–2.5 mm, proximal 1/5 indehiscent, connectives not splitting; Montana, Wyoming.	Penstemon caryi
32	Corollas 15–21 mm; styles 12–14 mm; pollen sacs 1.5–2 mm, connectives not splitting; Idaho, Nevada, Utah.	Penstemon idahoensis
31	Stems glabrous or retrorsely hairy, puberulent, pubescent, cinereous, or glandular-pubescent.	> 33
33	Caudices herbaceous, rhizomelike; corollas white to lavender; proximal bracts obovate to oblanceolate; stems 4–9 cm.	Penstemon debilis
33	Caudices woody; corollas blue to bluish violet, violet, or purple, rarely pinkish blue or lavender; proximal bracts ovate to elliptic, oblong, lanceolate, or linear, rarely oblanceolate; stems 5–85(–120) cm.	> 34
34	Thyrse axes glandular or glandular-pubescent, sometimes only distally, sometimes also retrorsely hairy.	> 35
35	Corollas funnelform, 13–16 mm; styles 8–10 mm.	Penstemon penlandii
35	Corollas ventricose, 14–35 mm; styles 10–23 mm.	> 36
36	Pollen sacs navicular to subexplanate, 1.2–1.4 mm, dehiscing completely; calyx lobe margins erose or lacerate; corolla tubes 2–3 mm.	Penstemon hallii
36	Pollen sacs navicular, navicular-sigmoid, or sigmoid, 1.1–3 mm, dehiscing incompletely; calyx lobe margins erose; corolla tubes 5–13 mm.	> 37
37	Pollen sacs sigmoid or navicular-sigmoid, sides glabrous or hispidulous to hispid or pubescent, hairs to 0.3 mm; corollas 18–35 mm, tubes 7–13 mm; leaves retrorsely hairy or glabrous; calyx lobes (4–)6–12(–13.5) mm.	> 38
38	Proximal bracts ovate to elliptic; pollen sacs: connectives not splitting; stems 7–27 cm.	Penstemon absarokensis
38	Proximal bracts lanceolate, rarely ovate or linear; pollen sacs: proximal 1/5–1/3 indehiscent, connectives not splitting; stems 7–80(–90) cm.	> 39
39	Pollen sacs 1.8–2.2 mm, sides sparsely hispid; stems retrorsely hairy; leaves retrorsely hairy.	Penstemon lemhiensis
39	Pollen sacs (1.8–)2–3 mm, sides glabrous or sparsely hispidulous; stems glabrous or retrorsely hairy to pubescent; leaves glabrous or retrorsely hairy.	Penstemon speciosus
37	Pollen sacs navicular, sides hispid, pubescent, or villous, hairs to 0.3–1 mm; corollas 17–33 mm, tubes 5–11 mm; leaves glabrous; calyx lobes 3.5–8 mm.	> 40
40	Pollen sac sides hispid or pubescent, hairs to 0.3 mm.	Penstemon saxosorum
40	Pollen sac sides pubescent to villous, hairs to 0.7–1 mm.	> 41
41	Corollas 18–25 mm, tubes 5–7 mm; styles 14–17 mm; staminodes glabrous or distal 1–3 mm sparsely pilose, hairs yellow or white, to 0.5 mm.	Penstemon compactus
41	Corollas 27–33 mm, tubes 9–11 mm; styles 17–21 mm; staminodes: distal 1–6 mm sparsely lanate, hairs yellowish, to 0.8 mm.	Penstemon moriahensis
34	Thyrse axes glabrous, retrorsely hairy, or puberulent, not glandular or glandular-pubescent.	> 42
42	Thyrse axes moderately to densely retrorsely hairy; corollas funnelform.	Penstemon fremontii
42	Thyrse axes glabrous, puberulent, glandular-pubescent, or ± glandular; corollas ventricose, rarely ventricose-ampliate or funnelform.	> 43
43	Pollen sac sides villous to lanate, rarely moderately pubescent, hairs to 0.7–2.5 mm.	> 44
44	Corollas sparsely white-villous internally abaxially; staminodes glabrous.	Penstemon navajoa
44	Corollas glabrous internally; staminodes glabrous or distal 1–6 mm pilose, villous, or lanate.	> 45
45	Leaves: basal and proximal cauline blades oblanceolate to linear, cauline blades linear; calyx lobes (6–)7–12 mm.	Penstemon caryi
45	Leaves: basal and proximal cauline blades oblanceolate to obovate, sometimes lanceolate, cauline blades oblanceolate to lanceolate or linear; calyx lobes (2.2–)3–8(–9) mm.	> 46
46	Pollen sac sides villous or lanate, hairs to 2.5 mm; cauline leaf blades oblanceolate to linear; corollas blue to pinkish blue or lavender; thyrses interrupted, secund, sometimes subsecund.	Penstemon comarrhenus
46	Pollen sac sides pubescent, villous, or lanate, hairs to 1.8 mm; cauline leaf blades oblanceolate to lanceolate or linear; corollas blue, lavender, violet, or purple; thyrses continuous or interrupted, cylindric or secund.	> 47
47	Cauline leaf blades oblanceolate to lanceolate, rarely linear, apices obtuse to acute; proximal bracts oblong to lanceolate, apices acute to acuminate; peduncles to 7 mm, pedicels 1–11 mm.	> 48
48	Corollas 18–25 mm, tubes 5–7 mm; styles 14–17 mm; staminodes glabrous or distal 1–3 mm sparsely pilose, hairs yellow or white, to 0.5 mm.	Penstemon compactus
48	Corollas 27–33 mm, tubes 9–11 mm; styles 17–21 mm; staminodes: distal 1–6 mm sparsely lanate, hairs yellowish, to 0.8 mm.	Penstemon moriahensis
47	Cauline leaf blades lanceolate to linear, apices acute or acuminate; proximal bracts lanceolate to linear, apices acuminate; peduncles to 20–27 mm, pedicels 1–20 mm.	> 49
49	Calyx lobes (4.5–)6–8(–9) × 2–3 mm, apices acuminate to caudate; pollen sac sides sparsely to densely lanate, hairs to 1 mm; staminodes: distal (2–)4–5 mm sparsely to moderately villous, hairs yellow or white, to 1 mm.	Penstemon strictiformis
49	Calyx lobes (2.5–)3–5 × 1.3–2.5 mm, apices acute, sometimes acuminate or obtuse; pollen sac sides moderately to densely lanate to villous, hairs to 1.8 mm; staminodes glabrous or distal 1–5 mm sparsely villous, hairs yellow or orange, to 0.7 mm.	Penstemon strictus
43	Pollen sac sides hispidulous, hispid, pubescent, hirsute, or pilose, hairs to 0.1–1 mm, rarely glabrous.	> 50
50	Pollen sacs navicular.	> 51
51	Corollas 24–48 mm, throats 8–13(–18) mm diam.; pollen sacs 1.4–2.5(–2.8) mm, connectives not splitting.	Penstemon glaber
51	Corollas 12–25(–30) mm, throats 4–11 mm diam.; pollen sacs 1.2–2(–2.2) mm, proximal 1/5–1/3 indehiscent, rarely only connectives not splitting.	> 52
52	Staminodes reaching orifices or slightly exserted, distal 3–5 mm villous, hairs yellow, to 1 mm; stems erect; corolla tubes 5–8 mm, throats 6–8 mm diam.	Penstemon saxosorum
52	Staminodes included or reaching orifices, distal 5–9 mm pilose to villous or lanate, hairs orange, yellow, or white, to 1 mm; stems decumbent, ascending, or erect; corolla tubes 5–11 mm, throats 4–11 mm diam.	> 53
53	Cauline leaf blades ovate or oblanceolate to lanceolate, bases cordate-clasping to clasping; calyx lobe apices acute to acuminate or cuspidate; stems decumbent to erect, 5–70(–90) cm.	Penstemon cyananthus
53	Cauline leaf blades oblanceolate to lanceolate or linear, bases tapered to truncate; calyx lobe apices acuminate, sometimes caudate; stems decumbent to ascending, 8–18(–25) cm.	Penstemon paysoniorum
50	Pollen sacs sigmoid or navicular-sigmoid.	> 54
54	Calyx lobes obovate to ovate, 2.5–4.5 mm, apices mucronate, sometimes acute to acuminate.	Penstemon cyaneus
54	Calyx lobes ovate to lanceolate, rarely obovate, 3.5–12(–13.5) mm, apices acute to acuminate, cuspidate, or caudate.	> 55
55	Calyx lobes (4–)6–12(–13.5) mm, glandular or glabrous; pollen sacs (1.8–)2–3 mm.	> 56
56	Proximal bracts ovate to elliptic; pollen sacs: connectives not splitting; stems 7–27 cm.	Penstemon absarokensis
56	Proximal bracts lanceolate, rarely ovate or linear; pollen sacs: proximal 1/3 indehiscent, connectives not splitting; stems 7–65(–90) cm.	Penstemon speciosus
55	Calyx lobes 3.5–8.5 mm, glabrous; pollen sacs 1.2–2.7(–2.8) mm.	> 57
57	Corollas 14–18(–20) mm; pollen sacs 1.2–1.7 mm, sides sparsely to moderately pilose, hairs to 0.5(–0.7) mm; calyx lobes 3.5–4.5 mm.	Penstemon cyanocaulis
57	Corollas (20–)24–35 mm; pollen sacs 1.8–2.4(–2.8) mm, sides hirsute or hispid, hairs to 0.3 mm; calyx lobes 4.5–8.5 mm.	> 58
58	Corollas (20–)24–30(–32) mm; staminodes: distal 0.5–1 mm moderately pilose, hairs to 0.8 mm, remaining distal 3–4 mm with scattered yellow hairs; cymes 1- or 2(or 3)-flowered.	Penstemon longiflorus
58	Corollas 29–35 mm; staminodes: distal 4–6 mm ± uniformly sparsely pilose, hairs to 1 mm; cymes 1–6-flowered.	Penstemon pennellianus