This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
1825-27. Pentstemon Digitalis Nutt. Trans. Am. Phil. Soc.
(II.) 5: 181. 1833-37. Pentstemon laevigatas var. Digitalis A. Gray, Syn.
Fl. 2: Part 1, 268. 1878.
Glabrous, except the glandular-pubescent inflorescence; stem rather stout, 2°-5° high. Lower and basal leaves oblong or oval, obtuse or acutish, entire or repand, 2' - 7' long, narrowed into margined petioles; upper leaves ovate, lanceolate or ovate-lanceolate, sessile and more or less cordate-clasping at the base, acuminate, sharply denticulate; thyrsus open, many-flowered; pedicels 1"-3" long; calyx-segments lanceolate, corolla white, 1' - 1 1/4' long, the tube abruptly dilated, the limb moderately 2-lipped, the throat open; sterile filament bearded above.
In fields and thickets, Maine to New York, Illinois, Kansas, Virginia and Arkansas. Doubtless escaped from cultivation in its northeastern range. May-July.
Glabrous except a few scattered hairs in the inflorescence and lines of puberulence on the inter-nodes, deep green. Leaves various, the basal spatulate, 2'-6' long, entire or undulate, with winged petioles; lower stem-leaves similar to the basal, the upper lanceolate or ovate-lanceolate, acute or acuminate, finely repand or distinctly serrate, rounded at the base and clasping; calyx-segments with a lanceolate base and a slender tip, often becoming 5" long; corolla purple, I2"-I5" long; sterile filament sparingly bearded.
On bluffs. Kentucky to Missouri, Alabama and Arkansas. May-June.
Pentstemon gracilis Nutt. Gen. 2: 52. 1818.
Glabrous or very nearly so up to the glandular-pubescent inflorescence; stem slender, strict, 6'-18' high. Basal and lower leaves linear-oblong or spatulate, mostly obtuse, denticulate, or entire, 1'-3' long, narrowed into margined petioles; upper leaves sessile, linear-lanceolate or the uppermost lanceolate, acuminate, denticulate; thyrsus open, several-many-flowered; pedicels 2"- 4" long; calyx-segments lanceolate, acute or acuminate; corolla purple, 9" - 12" long, its tube gradually enlarged above, its throat wide open; sterile filament bearded for about one-half its length; capsule one-third longer than the calyx.
On moist prairies, Manitoba to Minnesota, Missouri, Athabasca, Oklahoma and Colorado. May-July.
Pentstemon tubiflorus Nutt. Trans. Am. Phil. Soc. (II.) 5: 181. 1833-37.
Glabrous, except the viscid-pubescent calyx and pedicels; stem slender, strict, 2° - 3 1/2° high, leafless above. Leaves oblong, ovate, or lanceolate, 1' - 4' long, obtusish or acute, the basal narrowed into broad margined petioles, the upper sessile or clasping, entire or merely undulate; thyrsus narrow, interrupted, the clusters several-flowered; pedicels 1"- 3" long, calyx-segments ovate, acuminate, short, striate-nerved; corolla nearly funnelform, white or purplish, less than 1' long, nearly as broad when expanded, its tube gradually enlarged, the limb nearly equally five-lobed, the lobes spreading; sterile filament short bearded above; capsule ovoid, acute, about twice as long as the calyx.
In moist soil, Missouri, Kansas and Arkansas. May-July.