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See list of 8 species in this genus

Penstemon canescens (Britt.) Britt. was reported from ME by Pennell (1935). However, this species is relatively southern, reaching as far north as PA (Clements et al. 1998). The collection, if indeed determined accurately, would certainly represent an introduction. Reference: Clements et al. (1998).

  • 1a. Corolla red, strongly zygomorphic, the upper lip subgaleate, the lower lip with reflexed lobes; sterile stamen glabrous
  • 1b. Corolla white to pale purple or blue-purple to purple, weakly to moderately zygomorphic, the upper lip not resembling a galea, the lower lip with ascending to spreading lobes; sterile stamen pubescent, at least minutely near the apex
    • 2a. Corolla (35–) 40–50 mm long; calyx at anthesis 7–15 mm long; upper stem leaf blades broad-ovate to orbicular, subcordate to strongly clasping at the base, strongly glaucous
    • 2b. Corolla 15–35 mm long; calyx at anthesis 2.5–8 mm long; upper stem leaf blades lanceolate or narrow-ovate to elliptic, oblong, or narrow-oblong, rounded to truncate at the base, not or only thinly glaucous
      • 3a. Corolla weakly zygomorphic, the upper and lower lips not well-developed [Fig. 773], pubescent on both surfaces with minute, glandular hairs
      • 3b. Corolla zygomorphic, with conspicuous upper and lower lips, [Fig. 772] pubescent on the inner surface with eglandular hairs
        • 4a. Lower lip with an upward swelling, forming a palate that closes the orifice of the tubular corolla; corolla without purple lines on the inside of the tube; sterile filament densely pubescent
        • 4b. Lower lip without a palate, the orifice of the corolla open; corolla marked with fine purple lines on the inside of the tube; sterile filament sparsely to moderately pubescent or densely pubescent in P. pallidus
          • 5a. Corolla gradually widened distally, strongly ridged within, the lower lip much longer and projected forward compared with the upwardly flared or even recurved upper lip; leaf blades pubescent on both surfaces; stems pubescent
          • 5b. Corolla with a slender, basal tube and an evident, abrupt, dilated, distal portion, only moderately ridged within the tube, the lower lip only slightly longer and nearly of the same orientation as the upper lip; leaf blades glabrous or sparsely pubescent especially along the abaxial midvein; stems glabrous or pubescent only in lines of decurrence from the leaf bases
            • 6a. Anthers pubescent with stiff, white hairs up to 0.6 mm long; corolla white on the abaxial 
(i.e., outer) surface (sometimes faintly tinged with purple); capsules 9–12 mm long
            • 6b. Anthers glabrous (rarely with a few hairs on one or both locules that are up to 0.2 mm long); corolla pale purple to purple on the abaxial surface; capsules 5–8 mm long
              • 7a. Corolla 20–35 mm long; calyx lobes narrow-lanceolate to linear-subulate, 5–12 mm long; leaf blades often finely serrate; lower bracts of inflorescence (2–)5–32 mm wide, lanceolate to ovate (rarely linear), usually with serrate margins
              • 7b. Corolla 15–20 (–22) mm long; calyx lobes lanceolate to narrow-ovate, 3–6 mm long; leaf blades often obscurely serrate; lower bracts of inflorescence 1–3 mm wide, linear to lanceolate, usually with entire margins

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