Please try our next iteration of the Michigan Flora Online here. Beginning on February 1, 2023, will point to this new site.

The new site offers several benefits over the existing website, including real coordinate mapping, giving a clearer view of the density of documentation as well as more precision about plant distributions and their link to landforms. We will also have the ability to update species pages more regularly, both in terms of new collections and as more existing Michigan specimens are georeferenced. In addition, we have a better photo display, and offer indented keys.


1. Corolla ca. 3.3–4.5 cm long; upper leaves (if not all) broadly ovate, ± obtuse to rounded at apex and subcordate-clasping at base, strongly glaucous.

P. grandiflorus

1. Corolla not over 3 cm long; leaves narrower, very acute, often not glaucous.

2. Throat of corolla inflated, distinctly differentiated from the narrower tube; lower (3) lobes of corolla slightly longer than upper lobes; anthers usually at least sparsely bearded; stem glabrous below the inflorescence or rarely locally puberulent.

3. Anthers glabrous; calyx lobes linear-lanceolate.

P. calycosus

3. Anthers with at least a few bristly hairs (rarely glabrous) on the back (near attachment of the filament); calyx lobes lanceolate-ovate.

P. digitalis

2. Throat of corolla not sharply differentiated, only gradually expanded from the tube; lower lobes of corolla distinctly longer than the upper; anthers glabrous; stem ± uniformly puberulent to glandular-hairy from base to near the inflorescence.

4. Stem with numerous hairs 0.5–1 mm long (or even longer); lower lip humped, nearly closing throat of corolla; corolla (20–) 22–28 (–30) mm long, purple-lavender with whitish lips but not streaked with purple lines (nectar guides).

P. hirsutus

4. Stem with few or no hairs as long as 0.5 mm; lower lip not humped, the throat open; corolla (14–) 16–20 (–22) mm long, streaked with nectar guides (usually not visible on dry specimens).

5. Longest (lower) branches of inflorescence usually at least 2 cm long before first pedicels; cauline leaves puberulent on both surfaces (at least on main veins and margins); corolla white.

P. pallidus

5. Longest branches of inflorescence less than 2 cm before first pedicels; cauline leaves glabrous; corolla pale violet.

P. gracilis

All species found in Penstemon

Penstemon calycosusSMOOTH BEARD-TONGUE 
Penstemon digitalisFOXGLOVE BEARD-TONGUE 
Penstemon gracilisSLENDER BEARD-TONGUE 
Penstemon grandiflorusLARGE BEARD-TONGUE 
Penstemon hirsutusHAIRY BEARD-TONGUE 
Penstemon pallidusPALE BEARD-TONGUE 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. January 29, 2023.