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Key to Penstemon

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Show caption*© Scott Ward
1 Cauline leaves bipinnatifid (or merely deeply pinnatifid); basal leaves sessile; [endemic to GA]; [section Dissecti]
1 Cauline leaves entire or toothed; basal leaves petioled; [collectively widespread].
  2 Corolla 35-55 mm long; calyx 7-16 mm long (in flower).
    3 Stems glaucous and glaucous; leaves glaucous and glabrous; corolla glabrous internally and externally; [section Coerulei]
    3 Stems hairy; leaves not glaucous, hairy or not; corolla glandular-puberulent externally and internally in the throat; [section Cristati]
  2 Corolla 10-35 mm long; calyx 2.5-8 mm long (in flower).
image of plant
Show caption*© Alan Cressler: Penstemon multiflorus, along U.S. 1, Appling County, Georgia 2 by Alan Cressler
        5 Inflorescence with many nodes; anther cells dehiscing by short proximal slits; [s. GA south to s. FL]
image of plant
Show caption*© Scott Ward
image of plant
Show caption*© Scott Ward
        5 Inflorescence with <10 nodes; anther cells dehiscing their entire length; [collectively widespread].
image of plant
Show caption*© Paul Marcum
          6 Corolla weakly bilabiate, white, unlined, glandular-puberulent within; stem leaves abruptly reduced upwards
image of plant
Show caption*© Alan M. Cressler
          6 Corolla strongly bilabiate, white or variously pinkish to purplish, lined (except P. hirsutus and P. tenuiflorus), glabrous or pubescent with non-glandular hairs within; stem leaves gradually reduced upwards.
             7 Mid and upper stem (but below the inflorescence) glabrous or with short eglandular hairs distributed in patches or lines; lower lobes of the corolla essentially equaling the upper lobes; corolla throat not strongly 2-ridged within, the tube conspicuously dilated into the throat; [Penstemon digitalis complex].
image of plant
Show caption*© Paul Marcum
                 9 Corollas purplish to lavender; sepals linear-lanceolate, straight and attenuate, 5-9 mm long at anthesis; anthers glabrous to papillose
image of plant
Show caption*© Alan M. Cressler
image of plant
Show caption*© Scott Ward
image of plant
Show caption*© Richard & Teresa Ware
                 9 Corollas white with purple lines; sepals ovate to ovate-lanceolate, acuminate, 4.5-6.5 mm long at anthesis; anthers with several to many hairs
               8 Corollas 15-23 mm long.
                   10 Sepals 1.5-3.5 (-4.0) mm long; corollas white; [approaching our area in s. IN and s. IL]
                   10 Sepals 3-6 mm long; corollas white or tinged with lavender.
                     11 Leaves mostly 2.5-4 cm wide; anthers bearded with long papillae
image of plant
Show caption*© Gary P. Fleming
             7 Mid and upper stem (but below the inflorescence) pubescent throughout, consisting of short eglandular hairs and sometimes also with an overstory of longer glandular hairs; lower lobes of the corolla projecting beyond the upper lobes; corolla throat strongly 2-ridged on its floor, the tube also slightly to moderately dilated into the throat.
image of plant
Show caption*© Brian Finzel, some rights reserved (CC BY-SA), uploaded by Brian Finzel
                       12 Stem vestiture (mid and upper stem, but below the inflorescence) of short eglandular hairs only (or rarely also with a few glandular hairs in P. smallii).
                          13 Leaves 15-60 mm wide, 2.5-4× as long as wide; [Penstemon smallii complex].
                            14 Corollas 28-35 mm long, lavender, violet, or purple; staminodes 15-18 mm long, densely bearded in the upper 13-15 mm; largest leaf blades mostly 30-60 mm wide
                            14 Corollas 10-16 mm long, pale lavender, pink, violet, or almost white; staminodes 7-9 mm long, densely bearded in the upper 4-5 mm; largest leaf blades mostly 10-40 mm wide.
                              15 Leaves mostly 30-40 mm wide; corolla pale-lavender to whitish, usually strongly lined with dark purple; sepals linear-attenuate; [plants of dry to mesic calcareous uplands, of ne. AL and se. TN]
                              15 Leaves mostly 10-30 mm wide; corolla lavender, pink, or violet, inconspicuously lined with reddish-purple; sepals ovate-lanceolate; [plants of wetlands, of MS, LA, and westwards]
image of plant
Show caption*© Shaun Pogacnik, some rights reserved (CC BY-NC), uploaded by Shaun Pogacnik
                       12 Stem vestiture (mid and upper stem, but below the inflorescence) of a mixture of long glandular hairs and short eglandular hairs.
image of plant
Show caption*© Shaun Pogacnik, some rights reserved (CC BY-NC), uploaded by Shaun Pogacnik
                                16 Corolla throats closed or nearly so (the lower lip arching upwards and pressing against the upper lip); corollas unlined or very obscurely lined (except strongly lined in P. australis).
                                  17 Corollas unlined; inflorescence branches spreading-ascending, obviously diverging from the vertical inflorescence axis; [Penstemon hirsutus complex].
                                    18 Corollas tinged with purplish-violet, the lobes often white; leaves sparsely pubescent to glabrate, the pubescence often mainly restricted to the veins
                                    18 Corollas creamy-white throughout; leaves moderately to densely hairy across the surface
                                       19 Leaves moderately to densely glandular-woolly, especially along the major veins on the lower surface; stem leaf blades 6-20× as long as wide
image of plant
Show caption*© Alan M. Cressler
                                16 Corolla throats open, not as described above (except sometimes nearly closed in P. australis); corollas lined, at least internally; [Penstemon canescens complex].
image of plant
Show caption*© theo_witsell, some rights reserved (CC BY-NC), uploaded by theo_witsell
                                           21 Cauline leaf pairs (6-)8-12; stems retrorsely hairy but only sometimes ± glandular-pubescent distally; [sw. IL south to se AR, westward]
image of plant
Show caption*© abelkinser, some rights reserved (CC BY-NC)
                                           21 Cauline leaf pairs 4-8; stems retrorsely hairy AND consistently glandular pubescent or glandular-villous distally (also glandular-villous proximally in P. pallidus) ; [collectively widespread]
                                             22 Sepals 2-3.5 mm long, 1-1.5× as long as wide; corollas pale lavender (sometimes faded to white in herbarium specimens); inflorescences more open; cauline leaf margins finely and regularly toothed
                                             22 Sepals 3-5 mm long, 1.5-2.5× as long as wide; corollas creamy white, with violet lines; inflorescences more condensed; cauline leaf margins subentire or irregularly serrate or dentate
                                               23 Inflorescence branches erect-ascending, nearly paralleling the inflorescence axes; sepals 4-5.2 mm long; corollas 20-25 mm long; corolla:calyx length ratio 4-5; cauline leaf pairs 5-8
                                               23 Inflorescence branches spreading-ascending, obviously diverging from the vertical inflorescence axis; sepals 3.2-4.5 mm long; corollas 20-30 mm long; corolla:calyx length ratio 7-9; cauline leaf pairs 3-7