7. Penstemon tubaeflorus Nutt. (trumpet beard-tongue)

Pl. 485 d, e; Map 2219

Stems 30–100 cm long, erect or strongly ascending, glabrous (occasionally with 2 longitudinal lines of minute, glandular hairs extending partway to the stem base elsewhere), green or rarely slightly purplish-tinged, not glaucous. Basal leaves 2–11 cm long, the blade obovate to spatulate, rounded to bluntly pointed at the tip, tapered basally to a winged petiole, the margins entire or occasionally with sparse, minute, teeth, the surfaces glabrous, not glaucous. Stem leaves 1.5–14.0 cm long, relatively few toward the stem tip, variously lanceolate to oblong-lanceolate or narrowly ovate, bluntly to more commonly sharply pointed at the tip, sessile and mostly somewhat clasping, variously angled to rounded or cordate, the margins entire or with sparse, minute teeth, the surfaces glabrous, not glaucous. Inflorescences narrow panicles, the central axis glabrous or sparsely glandular-hairy near the nodes, green to dark green or rarely somewhat purplish-tinged, not glaucous, with 4–8 nodes (dense and with the upper nodes not clearly separable in robust plants), each with a pair of relatively small, linear to lanceolate, somewhat clasping bracts, the branches strongly ascending, with a pair of branched clusters per node, each with 3–10 or more flowers. Calyces 2.5–5.0 mm long at flowering, moderately to densely glandular-hairy, not glaucous, the lobes broadly lanceolate to ovate. Corollas 15–25 mm long, the tube slender, expanded evenly only toward the tip, nearly actinomorphic, only slightly bilabiate, the lobes spreading, the 3 lower lobes usually projecting slightly farther forward than the upper 2, white or the tube sometimes pale purplish-tinged toward the base, the throat lacking colored nectar guides and ridges, minutely glandular-hairy externally and in the throat. Staminode white, slightly flattened toward the tip, curled-under apically and relatively sparsely bearded with yellow or brown hairs. Fruits 7–10 mm long. Seeds 1.0–1.5 mm long, tan to dark brown or black, the tan to reddish brown ridges usually poorly developed. 2n=32. May–June.

Scattered to common in the southwestern quarter of the state, progressively less common to the north and east (Nebraska to Maine south to Texas and Mississippi; Canada). Upland prairies, glades, savannas, openings of mesic to dry upland forests, and rarely fens and openings of bottomland forests; also pastures, railroads, and roadsides.

Pennell (1935) hypothesized that the original distribution of P. tubaeflorus was confined largely to the Ozarks and surrounding areas, and that its present, broader distribution is the result of a relatively recent range expansion northward and eastward. This appears to be a natural spread along disturbance corridors such as roadsides. Plants in the northeastern states that are relatively tall and slender have sometimes been segregated as var. achoreus Fernald, but this distinction does not appear worthy of formal taxonomic segregation. Note that the species epithet sometimes has been erroneously spelled tubiflorus (Yatskievych and Turner, 1990; Gleason and Cronquist, 1991).