Penstemon sect. Penstemon

Treatment appears in FNA Volume 17. Treatment on page 183. Mentioned on page 82, 83, 93, 94, 184, 186, 191, 207, 235.

Herbs or subshrubs. Stems glabrous, glabrate, retrorsely hairy, puberulent, or pubescent, sometimes glandular-pubescent, glandular-lanate, or glandular-villous, rarely glutinous, glaucous or not. Leaves basal and cauline, sometimes basals absent or poorly developed, opposite, rarely whorled (P. deustus), subopposite (P. deustus, P. sudans), or alternate (P. gairdneri, P. seorsus), leathery or not, glabrous, glandular, puberulent, glandular-pubescent, glandular-lanate, retrorsely hairy, pubescent, or glabrate, not glaucous or rarely so (P. euglaucus, P. glaucinus), sometimes ± glaucescent (P. albomarginatus, P. griffinii, P. inflatus, P. oliganthus, P. tracyi); basal and proximal cauline petiolate; cauline sessile or petiolate, blade obovate, ovate, triangular-ovate, spatulate, oblanceolate, lanceolate, oblong, elliptic, or linear, rarely lyrate, margins entire or toothed. Thyrses continuous or interrupted, cylindric to conic, rarely secund, axis glabrous or glandular-pubescent, puberulent, pubescent, or retrorsely hairy, rarely glandular-lanate, cymes 1 or 2 per node; peduncles and pedicels spreading to ascending or erect. Flowers: calyx lobes: margins entire, erose, or lacerate, ± scarious, sometimes herbaceous, glandular-pubescent or glabrous, rarely glabrescent, puberulent, retrorsely hairy, glutinous, or glandular-ciliolate; corolla white, ochroleucous, pink, lavender, blue, violet, purple, or yellow, bilaterally symmetric, bilabiate or strongly bilabiate, rarely weakly bilabiate (P. tubaeflorus), not personate, sometimes personate (P. hirsutus, P. oklahomensis, P. tenuiflorus) or nearly personate (P. australis, P. degeneri, P. griffinii, P. laxiflorus, P. oliganthus), funnelform, tubular-funnelform, tubular, ampliate, or ventricose, glabrous, glabrate, glabrescent, or glandular-pubescent externally, glabrous or hairy internally abaxially, rarely glandular-pubescent abaxially and adaxially, throat slightly to abruptly inflated to slightly ventricose, not constricted at orifice, slightly to prominently 2-ridged adaxially, rarely rounded; stamens included or longer pair reaching orifice or exserted, filaments glabrous, pollen sacs opposite or divergent, rarely parallel, navicular to subexplanate or explanate, rarely saccate, dehiscing completely, rarely incompletely, distal 1/5–2/3 sometimes indehiscent, connective splitting, rarely not, sides glabrous, rarely hairy, sutures papillate, sometimes smooth; staminode included to exserted, flattened distally, 0.2–0.8(–1.1) mm diam., tip straight to recurved, distal 5–60(–90)% hairy, hairs to 3 mm, sometimes glabrous; style glabrous. Capsules glabrous, rarely glandular-puberulent distally. Seeds tan, brown, gray, or black, angled to slightly rounded, 0.4–2(–3.5) mm.


North America.


Species 62 (62 in the flora).

Elaborate subsectional classifications were presented by D. D. Keck (1945) and F. S. Crosswhite (1965b). Those are not followed; a more well-resolved phylogeny of the genus is needed.


null Penstemon East of the Rocky Mountains. > 1
1 Pollen sacs parallel, saccate, dehiscing incompletely. Penstemon multiflorus
1 Pollen sacs opposite or divergent, navicular, subexplanate, or explanate, dehiscing completely. > 2
2 Corollas glabrous externally. Penstemon procerus
2 Corollas glandular-pubescent externally. > 3
3 Corollas glandular-pubescent internally, without nectar guides; pollen sacs explanate. Penstemon tubaeflorus
3 Corollas hairy internally, not glandular-pubescent, with, sometimes without, nectar guides; pollen sacs navicular or subexplanate. > 4
4 Corollas personate, with or without nectar guides. > 5
5 Corollas lavender or purplish; leaves glabrous or sparsely glandular-lanate along midveins, rarely moderately glandular-lanate. Penstemon hirsutus
5 Corollas white to ochroleucous; leaves puberulent or retrorsely hairy, or moderately to densely glandular-lanate, especially along major veins abaxially. > 6
6 Leaves puberulent or retrorsely hairy; cauline leaf blades lanceolate to linear; Oklahoma, Texas. Penstemon oklahomensis
6 Leaves moderately to densely glandular-lanate, especially along major veins abaxially; cauline leaf blades ovate to lanceolate; Alabama, Kentucky, Mississippi, Tennessee. Penstemon tenuiflorus
4 Corollas not personate, sometimes nearly personate, with nectar guides. > 7
7 Stems glabrous or glabrate, puberulent, or retrorsely hairy. > 8
8 Corollas tubular to tubular-funnelform. > 9
9 Cauline leaf pairs (6–)8–12; corollas 15–19 mm; capsules 4–7 mm. Penstemon arkansanus
9 Cauline leaf pairs (3–)5–7; corollas 20–28(–30) mm; capsules 8–10 mm. Penstemon laxiflorus
8 Corollas ventricose, sometimes funnelform. > 10
10 Corollas (17–)20–35 mm; calyx lobes 4–9 mm. > 11
11 Pollen sac sides glabrous, rarely sparsely pubescent; calyx lobes 5–9 × 0.8–1.9 mm, apices acuminate; corollas pale lavender to violet. Penstemon calycosus
11 Pollen sac sides sparsely pubescent, rarely glabrous; calyx lobes 4–8 × 2–3 mm, apices acute to acuminate; corollas white, sometimes tinged lavender. Penstemon digitalis
10 Corollas 10–22 mm; calyx lobes 1.5–6 mm. > 12
12 Corollas 10–14 mm, funnelform; cauline leaf margins sharply serrate, sometimes ± serrate. Penstemon tenuis
12 Corollas 15–22 mm, ventricose; cauline leaf margins entire or denticulate, serrulate, or ± serrate. > 13
13 Calyx lobes 1.5–3.5(–4) mm; corollas white. Penstemon deamii
13 Calyx lobes 3–6 mm; corollas pale lavender to violet. Penstemon laevigatus
7 Stems retrorsely hairy and glandular-pubescent, glandular-lanate, or glandular-villous, sometimes sparsely and only distally. > 14
14 Corollas 28–35 mm; staminodes: distal 13–15 mm ± pilose; proximal bracts 56–130 × 23–55 mm, margins sharply serrate. Penstemon smallii
14 Corollas 10–30 mm; staminodes: distal 4–12 mm hairy; proximal bracts 3–95 × 1–45 mm, margins entire, ± dentate, ± crenate, serrulate, or serrate. > 15
15 Corollas ventricose. Penstemon canescens
15 Corollas tubular to tubular-funnelform. > 16
16 Corollas 20–28(–30) mm; styles 10–20 mm; capsules 6–10 mm. > 17
17 Stems retrorsely hairy and glandular-lanate, glandular hairs sometimes sparse; cymes each usually with only 1 branch elongating, other branches distinctly shorter. Penstemon australis
17 Stems puberulent to retrorsely hairy, rarely also glandular-pubescent distally; cymes each usually with all branches elongating and of equal length. Penstemon laxiflorus
16 Corollas 10–24 mm; styles 9–17 mm; capsules 4–8 mm. > 18
18 Corollas light lavender to lavender or purple; calyx lobes (1.5–)2–6 mm. > 19
19 Calyx lobes (1.5–)2–3.5 mm; cauline leaves 11–32 mm wide, blades ovate to lanceolate or oblanceolate. Penstemon brevisepalus
19 Calyx lobes 4–6 mm; cauline leaves (2–)4–10(–15) mm wide, blades lanceolate to linear. Penstemon gracilis
18 Corollas white, sometimes tinged lavender or blue; calyx lobes (2–)2.8–5.5 mm. > 20
20 Corollas 10–16 mm; cauline leaves 120–150 × 30–40 mm. Penstemon kralii
20 Corollas 15–22 mm; cauline leaves 22–100 × 4–24 mm. > 21
21 Stems retrorsely hairy, sometimes also ± glandular-pubescent distally; leaves glabrous or sparsely retrorsely hairy, especially along midveins and margins abaxially, glabrous or sparsely puberulent adaxially; cauline leaves (6–)8–12 pairs, blades lanceolate. Penstemon arkansanus
21 Stems retrorsely hairy and glandular-villous proximally, retrorsely hairy and glandular-pubescent distally, glandular hairs sometimes sparse; leaves sparsely to densely pubescent, sometimes also with scattered glandular hairs abaxially, sparsely pubescent adaxially; cauline leaves 4–8 pairs, blades ovate to lanceolate. Penstemon pallidus
null Penstemon from the Rocky Mountains Westward. > 1
1 Subshrubs; leaves alternate, subopposite, whorled, or opposite. > 2
2 Leaves: margins dentate, dentate-serrate, serrate, or serrulate. > 3
3 Thyrse axes, peduncles, pedicels, and calyx lobes ± glandular-pubescent. Penstemon deustus
3 Thyrse axes, peduncles, pedicels, and calyx lobes densely glandular-pubescent. Penstemon sudans
2 Leaves: margins entire. > 4
4 Corollas white to ochroleucous, sometimes tinged lavender (abaxial lobes sometimes brown). Penstemon deustus
4 Corollas blue to violet or purple. > 5
5 Corollas glandular-pubescent internally. Penstemon gairdneri
5 Corollas glabrous internally. Penstemon seorsus
1 Herbs; leaves opposite. > 6
6 Corollas glabrous externally; calyx lobes glabrous, rarely puberulent, retrorsely hairy, glandular-pubescent, or glandular-ciliolate. > 7
7 Corollas yellow or light yellow. > 8
8 Corollas 6–11 mm; pollen sacs 0.4–0.5 mm; staminodes 0.3–0.4 mm diam., distal 0.5–1 mm pilose. Penstemon confertus
8 Corollas 12–16 mm; pollen sacs 0.7–0.9 mm; staminodes 0.4–0.7 mm diam., distal 2–3 mm moderately pilose. Penstemon flavescens
7 Corollas white, ochroleucous, pink, pinkish lavender, lavender, blue, violet, or purple. > 9
9 Pollen sacs dehiscing incompletely, distal 1/5–1/4 indehiscent. Penstemon globosus
9 Pollen sacs dehiscing completely. > 10
10 Staminodes glabrous. > 11
11 Proximal bracts oval to oblong; corollas pinkish lavender, 13–18 mm. Penstemon albomarginatus
11 Proximal bracts lanceolate to linear; corollas violet, blue, purple, lavender, or white, 7–15 mm. > 12
12 Corollas white or lavender. Penstemon pratensis
12 Corollas violet to blue or purple. Penstemon procerus
10 Staminodes hairy. undefined
13 Stems glabrous, glutinous, usually covered with sand; caudices rhizomelike. Penstemon arenarius
13 Stems glabrous, retrorsely hairy, or puberulent, not glutinous and covered with sand; caudices not rhizomelike. > 14
14 Stems and leaves glaucous. Penstemon euglaucus
14 Stems and leaves not glaucous, rarely glaucescent. > 15
15 Proximal bracts elliptic to ovate; thyrses 2–4 cm; stems 8–12 cm. Penstemon tracyi
15 Proximal bracts lanceolate to linear, rarely ovate; thyrses 0.5–23(–50) cm; stems 3–70(–120) cm. > 16
16 Calyx lobes 1–1.8 mm, apices truncate to cuspidate; corollas 7–9(–11) mm. Penstemon cinicola
16 Calyx lobes 1.2–8 mm, apices truncate to obtuse, acute, short- to long-caudate, short- to long-cuspidate, acuminate, or mucronate; corollas 6–20 mm. > 17
17 Leaves essentially cauline, basal absent or poorly developed. > 18
18 Corollas densely yellow-villous internally abaxially; pollen sacs explanate; stems ± retrorsely hairy. Penstemon laxus
18 Corollas sparsely white-villous internally abaxially; pollen sacs navicular; stems glabrous or sparsely puberulent. Penstemon watsonii
17 Leaves basal and cauline, basal sometimes poorly developed. > 19
19 Corollas yellow, white, ochroleucous, pink, or lavender; calyx lobes glabrous. > 20
20 Pollen sacs explanate, 0.4–0.5 mm; corollas 6–11 mm. Penstemon confertus
20 Pollen sacs navicular, 0.6–0.8 mm; corollas 10–15 mm. Penstemon pratensis
19 Corollas violet to blue or purple; calyx lobes glabrous, retrorsely hairy, or puberulent. > 21
21 Corollas 7–11 mm, throats 2–3 mm diam.; pollen sacs explanate, 0.3–0.6 mm. Penstemon procerus
21 Corollas 10–20 mm, throats 3–4.5 mm diam.; pollen sacs navicular, 0.5–1.1 mm. Penstemon rydbergii
6 Corollas glandular-pubescent externally, rarely glabrescent; calyx lobes glandular-pubescent, rarely glabrous or glabrescent. > 22
22 Pollen sac sides sparsely puberulent. Penstemon bleaklyi
22 Pollen sac sides glabrous. > 23
23 Capsules glandular-pubescent distally. Penstemon whippleanus
23 Capsules glabrous. > 24
24 Thyrses ± conic, interrupted; peduncles and pedicels spreading to ascending or erect. > 25
25 Cauline leaf blades oblanceolate to lanceolate or linear, rarely ovate, margins entire; staminodes: distal 6–10 mm pilose. > 26
26 Pollen sacs 0.9–1.1 mm; corollas 14–19 mm; Colorado. Penstemon degeneri
26 Pollen sacs 1.3–1.6 mm; corollas 17–27 mm; New Mexico. Penstemon inflatus
25 Cauline leaf blades oblong to ovate, triangular-ovate, or lanceolate, margins serrulate, serrate, or dentate, sometimes entire; staminodes: distal 1–5 mm pilose to villous. > 27
27 Thyrse axes sparsely to moderately glandular-pubescent; calyx lobes ovate, margins broadly scarious. Penstemon wilcoxii
27 Thyrse axes moderately to densely glandular-pubescent; calyx lobes ovate to lanceolate, margins narrowly to broadly scarious. > 28
28 Corollas 15–22 mm; staminodes: distal 1–2 mm densely pilose, hairs yellow; cauline leaf blades oblong to ovate or triangular-ovate. Penstemon ovatus
28 Corollas 12–18 mm; staminodes: distal 2–3 mm sparsely to moderately pilose, hairs yellow or yellow-orange; cauline leaf blades lanceolate to oblong. Penstemon subserratus
24 Thyrses cylindric or secund, continuous or interrupted; peduncles and pedicels ascending to erect. > 29
29 Stems and leaves glaucous; corollas without nectar guides. Penstemon glaucinus
29 Stems and leaves not glaucous, leaves rarely ± glaucescent (P. griffinii, P. oliganthus); corollas with, sometimes without, nectar guides. > 30
30 Caudices rhizomelike; leaves cauline; alpine talus, gravel slopes, boulder fields, 3200–4200 m. Penstemon harbourii
30 Caudices not rhizomelike; leaves basal and cauline, basal sometimes poorly developed, rarely absent; prairies, meadows, woodlands, forests, 30–3900 m. > 31
31 Staminodes exserted; corollas ventricose, ventricose-ampliate, or ampliate. > 32
32 Corollas 13–18 mm; styles 10–13 mm; staminodes: distal 2–6 mm sparsely pilose, hairs yellow, to 0.6 mm, rarely glabrous; pollen sacs 0.8–1.2 mm. Penstemon anguineus
32 Corollas 20–30 mm; styles 16–19 mm; staminodes: distal 6–10 mm sparsely to moderately lanate, hairs yellow or white, to 3 mm; pollen sacs 1.2–1.5 mm. Penstemon rattanii
31 Staminodes included or reaching orifices, rarely slightly exserted; corollas tubular, tubular-funnelform, or funnelform. > 33
33 Proximal cauline leaves 1–5(–7) mm wide, blades linear to narrowly elliptic or narrowly oblanceolate, margins entire. > 34
34 Calyx lobes ovate to lanceolate, 2.2–4.6 × 1–2.4 mm; stems 6–20(–25) cm; corollas 11–17 mm, blue to violet. Penstemon aridus
34 Calyx lobes obovate to ovate or lanceolate, 1.5–3 × 0.7–1.5 mm; stems 20–50(–65) cm; corollas 8–10 mm, violet to light blue, pink, or light purple. Penstemon peckii
33 Proximal cauline leaves 2–55 mm wide, blades triangular to ovate, lanceolate, oblanceolate, elliptic, obovate, or spatulate, margins serrate, dentate, serrulate, denticulate, or entire. > 35
35 Leaves essentially cauline, basal absent or poorly developed; cauline leaf blade margins entire. Penstemon radicosus
35 Leaves basal and cauline; cauline leaf blade margins serrate, dentate, serrulate, denticulate, or entire. > 36
36 Caudices herbaceous; corollas tubular. Penstemon gracilis
36 Caudices not herbaceous; corollas tubular, tubular-funnelform or funnelform. > 37
37 Thyrses secund; proximal bracts lanceolate to linear. > 38
38 Cauline leaf blades linear; corollas densely golden-villous internally abaxially, hairs passing onto limbs (and deep into throats), 17–25 mm; Colorado, New Mexico. Penstemon griffinii
38 Cauline leaf blades oblanceolate to lanceolate; corollas sparsely to moderately white-villous to white-lanate internally abaxially, 11–20 mm; Arizona, New Mexico. Penstemon oliganthus
37 Thyrses cylindric to conic, rarely ± secund; proximal bracts ovate to lanceolate. > 39
39 Corollas light yellow; leaves glabrous. Penstemon flavescens
39 Corollas blue, lavender, violet, bluish purple, or purple, rarely light yellow or whitish; leaves glabrous or puberulent to retrorsely hairy, pubescent, or glandular-pubescent. > 40
40 Corollas 9–12 mm, throats 2–3 mm diam.; pollen sacs 0.5–0.6 mm; thyrses 1–6 cm; Washington. Penstemon washingtonensis
40 Corollas (7–)8–23 mm, throats 3–9 mm diam.; pollen sacs 0.5–1.2 mm; thyrses 1–39 cm; widespread, including Washington. > 41
41 Stems and leaves glaucous. Penstemon glaucinus
41 Stems and leaves not glaucous. > 42
42 Basal and proximal cauline leaf blades triangular to ovate or lanceolate; peduncles and pedicels spreading to ascending; corolla throats 4–9 mm diam. Penstemon wilcoxii
42 Basal and proximal cauline leaf blades ovate to obovate, lanceolate, oblanceolate, elliptic, or spatulate; peduncles and pedicels ascending to erect; corolla throats 3–6 mm diam. > 43
43 Staminodes: distal 4–6 mm villous or pilose. > 44
44 Pollen sacs 0.9–1.2 mm; cauline leaves 12–27 mm wide; peduncles and pedicels erect; corollas 16–20 mm, tube 5–7 mm; calyx lobes lanceolate. Penstemon metcalfei
44 Pollen sacs 0.5–0.8 mm; cauline leaves 1–14 mm wide; peduncles and pedicels ascending to erect; corollas (7–)8–19 mm, tube 2–5 mm; calyx lobes ovate to lanceolate. > 45
45 Leaves glabrous, retrorsely hairy, or puberulent, blade margins entire, sometimes serrulate or serrate; California, Colorado, Idaho, Montana, Nevada, Oregon, Utah, Washington, Wyoming. Penstemon humilis
45 Leaves glabrous, blade margins serrulate or denticulate, sometimes entire; Colorado, Wyoming. Penstemon virens
43 Staminodes: distal 0.5–4 mm villous or pilose. > 46
46 Corollas essentially without nectar guides; leaves glabrous; blade margins entire. Penstemon heterodoxus
46 Corollas with nectar guides; leaves retrorsely hairy, puberulent, or glabrous; blade margins ± serrulate, serrate, dentate, denticulate, or entire. > 47
47 Staminodes 9–12 mm; corollas 14–23 mm, throats 5–6 mm diam. Penstemon elegantulus
47 Staminodes (3–)6–10 mm; corollas 7–20 mm, throats 3–6 mm diam. > 48
48 Cauline leaf blade margins serrulate to serrate or dentate, sometimes entire; proximal bract margins serrate to serrulate, sometimes entire; cymes 3–11-flowered. > 49
49 Pollen sacs 0.6–0.8 mm; staminodes: distal 0.5–1 mm densely pilose, hairs yellow, to 0.8 mm; basal and cauline leaves retrorsely hairy or pubescent, sometimes also glandular-pubescent; cauline leaf blades triangular-ovate to lanceolate. Penstemon pruinosus
49 Pollen sacs 0.7–1.1 mm; staminodes: distal 2–3 mm sparsely to moderately pilose, hairs yellow or yellow-orange, to 1.5 mm; basal and cauline leaves glabrous or puberulent; cauline leaf blades lanceolate to oblong. Penstemon subserratus
48 Cauline leaf blade margins entire, sometimes ± serrulate, or dentate, rarely ± serrate; proximal bract margins entire or ± serrate to dentate; cymes (1–)2–8(–11)-flowered. > 50
50 Pollen sacs saccate, dehiscing incompletely, distal 1/5 or less sometimes indehiscent. Penstemon attenuatus
50 Pollen sacs navicular, subexplanate, or explanate, dehiscing completely. > 51
51 Staminodes 9–12 mm; pollen sacs 0.9–1.2 mm; corollas 14–23 mm. Penstemon elegantulus
51 Staminodes (3–)6–9 mm; pollen sacs 0.5–1.2 mm; corollas 7–20 mm. > 52
52 Basal and proximal cauline leaf margins ± serrate or dentate; pollen sacs subexplanate to explanate. Penstemon albertinus
52 Basal and proximal cauline leaf margins entire, sometimes denticulate, serrate, or serrulate; pollen sacs navicular to subexplanate. > 53
53 Cauline leaves 1–3 pairs, sessile, bases truncate; proximal bracts 2–7 mm wide; staminodes: distal 0.5–1.5 mm densely pilose, hairs to 0.7 mm. Penstemon spatulatus
53 Cauline leaves (1–)2–5(–7) pairs, sessile or proximals short- to long-petiolate, bases tapered to clasping; proximal bracts 1–15(–28) mm wide; staminodes: distal 1–4 mm sparsely to densely pilose, hairs to 1.2 mm. > 54
54 Stems glabrous or retrorsely hairy; cauline leaves 2–25(–38) mm wide; peduncles and pedicels erect; calyx lobe margins erose to lacerate, apices acuminate to short-caudate or long-acuminate; pollen sacs 0.6–1.2 mm; staminodes 0.3–0.4 mm diam. Penstemon attenuatus
54 Stems retrorsely hairy; cauline leaves 1–11 mm wide; peduncles and pedicels ascending to erect; calyx lobe margins entire or erose, apices acute; pollen sacs 0.5–0.8 mm; staminodes 0.1–0.3 mm diam. Penstemon humilis