5. Penstemon pallidus Small (pale beard-tongue)
Pl. 485 a–c; Map
2217
Stems 25–60 cm
long, erect or ascending, densely pubescent with minute, nonglandular hairs,
also with moderate to dense, longer, glandular hairs, green to grayish green,
not glaucous. Basal leaves 2–12(–18) cm long, the blade oblanceolate to
spatulate, obovate or elliptic, rounded to bluntly pointed at the tip, tapered
basally to a usually winged petiole, the margins entire or nearly so to bluntly
or sharply and sometimes minutely toothed, the surfaces moderately to densely
pubescent with shorter nonglandular and longer glandular hairs, sometimes
mostly along the margins and main veins, not glaucous. Stem leaves 2–10 cm
long, the lowermost with the blade oblanceolate to narrowly oblong-elliptic or
narrowly ovate, grading into lanceolate or narrowly lanceolate at the stem tip,
bluntly to sharply pointed at the tip, sessile or nearly so, the base of the
lower blades tapered, grading through rounded to those of the uppermost leaves
usually shallowly cordate and clasping, the margins entire or nearly so to
bluntly or sharply and sometimes minutely toothed, at least above the midpoint,
the surfaces pubescent with shorter nonglandular and longer glandular hairs,
sometimes mostly along the margins and main veins, not glaucous. Inflorescences
narrow to occasionally more broadly pyramidal panicles, the central axis
densely glandular-hairy, green to grayish green, not glaucous, with 3–8 nodes,
each with a pair of relatively small, linear to narrowly lanceolate, somewhat
clasping bracts, the branches loosely to strongly ascending or arched upward,
with a pair of few-to several-branched clusters per node, each main branch with
2–9(–16) flowers. Calyces 3–5 mm long at flowering, densely glandular-hairy,
not glaucous, the lobes ovate. Corollas 17–23 mm long, the tube abruptly but
relatively slightly enlarged at about the midpoint (usually very slightly so on
the lower side), strongly bilabiate, the upper lip spreading to somewhat
recurved, the lower lip slightly spreading to nearly straight, white or
occasionally pale pinkish- to purplish-tinged, the throat appearing slightly
flattened, relatively strongly 2-ridged and usually lined with purple 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, white-hairy on the upper surface, slightly curved
downward apically and bearded with yellow hairs. Fruits 5–7 mm long. Seeds
0.5–0.8 mm long, brown to dark brown, the tan to reddish brown ridges usually
poorly developed. 2n=16. April–July.
Scattered to
common nearly throughout the state, but absent or uncommon in the southern
portion of the Mississippi Lowlands Division and the western half of the
Glaciated Plains (eastern U.S. west to Minnesota, Kansas, and Arkansas;
Canada). Glades, ledges and tops of bluffs, upland prairies, savannas, and
openings of dry upland forests; also pastures, old fields, quarries, railroads,
and roadsides; on both acidic and calcareous substrates.
This species is
morphologically similar to P. arkansanus. For further discussion, see
the treatment of that species. Steyermark (1963) noted that this species
usually appears hairier than other members of the genus in Missouri. Pennell
(1935) hypothesized that the colonization of P. pallidus into much of
the easternmost states occurred relatively recently.