Flora of the Southeastern United States

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]

      4 Corolla white to pink

      4 Corolla purple or violet

  2 Corolla 10-35 mm long; calyx 2.5-8 mm long (in flower).

        5 Inflorescence with many nodes; anther cells dehiscing by short proximal slits; [s. GA south to s. FL]

        5 Inflorescence with <10 nodes; anther cells dehiscing their entire length; [collectively widespread].

          6 Corolla weakly bilabiate, white, unlined, glandular-puberulent within; stem leaves abruptly reduced upwards

          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].

               8 Cauline leaves serrate (the teeth pointed slightly inward, parallel with the leaf blade); corolla 20-35 mm long (measured from corolla base to petal tips), pale lavender to violet; sepals linear-lanceolate, 5-9 mm long at anthesis, the apices acuminate; anthers glabrous (sometimes papillose, but lacking hispid hairs)

               8 Cauline leaves entire or denticulate to serrulate (the marginal teeth short if present and pointed outward, perpindicular from the blade); corolla 15-23 mm long (if 20-35 mm long as in P. digitalis, then the anther sacs with long tufted white hairs).

                 9 Stems glabrous, often slightly glaucous; corolla 20-35 mm long, primarily white (sometimes lightly tinged with lavender); anther sacs purple, with tufts of white hispid hairs to 0.6 mm in length; capsules 8-14 mm long

                 9 Stems puberulent to retrorsely pubescent (at least proximally), if glabrous, then never glaucous; corolla 15-23 mm long, primarily pale lavender to purple (except P. deamii); anther sacs glabrous or if bearing white hairs these short and stiff (≤ 0.2 mm long); capsules 5-8 (-9) mm long.

                   10 Sepals 1.5-3.5 (-4.0) mm long; corollas white; stems retrorsely pubescent (at least proximally); [endemic to s. IN and s. IL]

                   10 Sepals 3-6 mm long; corollas white, white and tinged with lavender, or pale lavender to violet; stems glabrous, puberulent or retrorsely pubescent; [collectively more widespread, including s. IN and s. IL].

                     11 Leaves mostly 2.5-4 cm wide; corolla primarily white, sometimes tinged lavender; anthers bearing long papillae; [occurring primarily within the Ohio and upper MS River valleys, scattered southward]

                     11 Leaves mostly 1.5-2.5 cm wide; corolla pale lavender to violet; anthers glabrous or short-papillose; inflorescence axis glabrous or with a mix of retrorse and sparsely glandular pubescence; [primarily occurring in the southeastern piedmont and coastal plain, also occurring northwestward into the interior plateau region]

             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.

                       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 4-28 mm wide, 4-5× as long as wide

                          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]

                       12 Stem vestiture (mid and upper stem, but below the inflorescence) of a mixture of long glandular hairs and short eglandular hairs.

                                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 lined; inflorescence branches erect-ascending, nearly paralleling the inflorescence axes

                                  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 puberulent or retrorsely hairy; stem leaf blades 3-8× as long as wide

                                       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

                                16 Corolla throats open, not as described above (except sometimes nearly closed in P. australis); corollas lined, at least internally; [Penstemon canescens complex].

                                         20 Corollas 14-23 mm long.

                                           21 Cauline leaf pairs (6-)8-12; stems retrorsely hairy but only sometimes ± glandular-pubescent distally; [sw. IL south to se AR, westward]

                                           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

                                         20 Corollas 20-32 mm long.

                                               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