3. Penstemon digitalis Nutt. ex Sims (smooth beard-tongue, tall white beard-tongue)

P. alluviorum Pennell

Pl. 485 f, g; Map 2215

Stems 25–90(–140) cm long, erect or ascending, usually glabrous, but sometimes moderately to densely pubescent toward the tip with minute, usually nonglandular hairs, these often in longitudinal lines, green to olive green or more commonly purplish-tinged, at least toward the base, often somewhat shiny, not glaucous. Basal leaves 3–20 cm long, the blade oblanceolate to spatulate or obovate, rounded to bluntly or sharply pointed at the tip, tapered basally to a usually winged petiole, the margins entire or nearly so or bluntly to sharply and sometimes finely toothed, the surfaces glabrous or occasionally minutely hairy along the main veins, the undersurface often dotted with minute sessile glands, not glaucous. Stem leaves 2.5–18.0 cm long, the lowermost with the blade oblanceolate to narrowly oblong-elliptic, grading into ovate, lanceolate, or narrowly lanceolate toward the stem tip, mostly sharply pointed at the tip, sessile or nearly so, the base of the lower blades tapered, grading through rounded to those of at least the uppermost leaves often shallowly cordate and clasping, the margins variously entire to bluntly or sharply, irregularly, and sometimes minutely toothed, the surfaces glabrous or occasionally minutely hairy along the main veins, the undersurface often dotted with minute sessile glands, not glaucous. Inflorescences narrow to more broadly pyramidal panicles, the central axis sparsely to moderately glandular-hairy, sometimes also nonglandular-hairy, green or purplish-tinged, not glaucous, with (2–)3–6 nodes, each with a pair of relatively small, linear to narrowly lanceolate, somewhat clasping bracts, the branches ascending or arched upward, with a pair of few- to several-branched clusters per node, each main branch with 3–18 flowers. Calyces (3–)4–8 mm long at flowering, moderately to densely glandular-hairy, not glaucous, the lobes narrowly ovate to ovate, angled or only slightly tapered to the sharply pointed tips. Corollas (18–)20–30 mm long, the tube abruptly enlarged at or more commonly below the midpoint, strongly bilabiate, the upper lip spreading to slightly recurved, the lower lip spreading to strongly arched downward, not projecting significantly beyond the upper lip, white or occasionally pale pinkish- to purplish-tinged, the throat not appearing flattened, only slightly 2-ridged and usually lined with purple and/or pink and occasionally also yellow nectar guides on the lower side, minutely glandular-hairy externally and sparsely to moderately nonglandular-hairy in the throat. Staminode white, strongly flattened toward the tip, sometimes somewhat curved or curled downward apically, bearded on the upper surface above the midpoint, the hairs yellow or purple toward the base, yellow to yellowish brown toward the tip. Fruits 10–15 mm long. Seeds 0.8–1.3 mm long, tan to dark brown or black, the tan to reddish brown ridges sometimes well-developed. 2n=96. April–June.

Scattered to common nearly throughout the state, but absent or uncommon in much of the western half of the Glaciated Plains Division (eastern U.S. west to South Dakota and Texas; Canada). Bottomland forest, mesic to dry upland forests, savannas, glades, ledges and tops of bluffs, upland prairies, sand prairies, bottomland prairies, sloughs, oxbows, banks of streams, marshes, and fens; also pastures, old fields, fallow fields, fencerows, ditches, railroads, and roadsides.

This is the most abundant and morphologically variable species of Penstemon in the state. Pennell (1935) and Steyermark (1963) maintained P. alluviorum as a separate species, but most recent authors (Koelling, 1964; Cooperrider, 1976; Gleason and Cronquist, 1991) have considered it to represent merely small-flowered plants of P. digitalis. The rare f. baueri Steyerm. was described from a single historical population in Osage County in which the leaves occur in whorls of three at most stem nodes. Pennell (1935) hypothesized that the original distribution of P. digitalis was confined largely to the western and southern portions of its present range and that its presence in much of the eastern United States is a relatively recent phenomenon. It is difficult to know with certainty what the extent of the species’ distribution might have been prior to European colonization, but it apparently has been successful in using disturbance corridors such as railroads and roads to spread naturally into new areas.