Foxglove beardtongue (Penstemon digitalis) of the Plantain (Plantaginaceae) family, formerly of the Figwort (Scrophulariaceae) family, is the largest of five white-flowered beardtongues in Arkansas. It is found throughout much of the eastern U.S. The genus name is from Greek words translating to “five stamens.” The specific epithet refers to the foxglove-like flowers of the genus Digitalis. Another common name is smooth white penstemon. The common name of the genus, “beardtongue,” describes the sterile, typically hairy (bearded) fifth stamen (a staminode) that is characteristic of all Penstemon species. Preferred habitats are well-drained, mesic, loamy soils in sunny prairies, sunny road drainages and partially sunny woodlands.
Plants have a thick clump of light colored fibrous roots and a woody caudex that may produce adjacent off-set plants. Ground-hugging basal leaves may survive winter and be present when spring growth appears. Mature caudices have multiple growth points that produce multiple stems 1 to 3 inches long bearing basal leaves only as well as one to several slender flowering stems from 3 to 4 feet tall. The unbranched flowering stems, becoming erect with maturity, are sturdy and very smooth (glabrous). The only pubescence on the plant occurs in the inflorescence.
Photo 1: In mid-March, along with over-wintering basal leaves, several rosettes of new leaves have appeared. New leaves are on stems that will either remain short with leaves only while other new leaves are of stems that will become tall and produce flowers.
Photo 2: In this mid-April photo, rapidly growing flowering stems are not erect but will become erect with further growth.
Basal leaves occur as closely spaced, decussate (rotated 90 degrees) and opposite pairs on the short stems. Leaves, with smooth margins, are a shiny medium green on the upper surfaces and a lighter green below. Basal leaves, with a total length to 11 inches, have a lanceolate blade to 5 inches long and a tapering winged petiole to 6 inches long. Young basal leaves and over-wintering leaves may have purplish shading, especially along petioles and lower blade surfaces. Leaf midribs are sunken above and sharply raised below. Widely spaced secondary pinnate veins curve gently toward leaf apex, but fade away without reaching leaf margin. Tertiary veins are obscure. Veins are the same color as leaf blade except lower-surface veins are a light yellowish green. Basal leaves persist after the flowering/fruiting stems have dried; a few that are ground-hugging persist into spring.
Leaves on flowering stems (cauline leaves) are in widely spaced (to 6 inches apart) opposite decussate pairs. These leaves, sessile to clasping, are lanceolate to oblanceolate, becoming small and elongate-triangular below the inflorescence. Generally, leaves have a rounded base and a long-tapering acute apex. Lowermost leaves may have wings that widen toward the base. Leaf length ranges from 8 inches, along lower portion of stem, to 2 inches and less, just below the inflorescence. Margins tend to be finely dentate, with teeth of lower leaves widely spaced and those of upper leaves more closely spaced. Leaf coloration is about the same as that of basal leaves. Venation is also about the same, but secondary veins are more closely spaced.
Photo 3: Two basal leaves (11 inches long) are displayed at bottom of photo with other leaves being cauline leaves. Upper leaf surfaces shown on left and lower surfaces shown on right.
In mid- to late-spring, the terminal inflorescence occurs as opposite pairs of branched ascending clusters (cymes), beginning about 6 inches above last leaf pair. Three to five opposite pairs of primary cymes tend to compose an inflorescence with spacing between pairs decreasing upwards to a cluster of flowers. Cymes are generally branched into secondary cymes. Primary and secondary cymes are subtended by decreasingly small linear bracts that have broadened, clasping bases. Each division of a cyme tends to have one to three flowers per branch. A terminal inflorescence has a length to 8+ inches and a width of up to 3 inches.
Photo 4: The terminal inflorescence is an elongate cluster of cymes. Photo taken in mid-May.
Foxglove beardtongue’s cream colored flower buds have a bulbous appearance before opening as white (sometimes with purplish shades) swollen corollas to 1½ inches long. Corolla tube abruptly enlarges to become strongly two-lipped (bilabiate), the lower lip with three larger lobes, the upper with two slightly smaller lobes. All five lobes, broadly rounded at their distal ends, have a similar appearance and similar length. Corollas, more broad than high, with a nearly flat lower inner surface, may have a few longitudinal purple veins (insect guides) along lower portion of the tube. Flowers are perfect (both male and female parts) with four fertile stamens and a pistil along with a prominent staminode. Two pairs of stamens, attached to the corolla tube, arise from the flower’s center so that their anthers are positioned at the top of the enlarged portion of tube. Anthers are held in see-saw fashion at tips of filaments. Style, straight with the small stigma, is centered between and in close proximity to the two anther pairs. The staminode, centrally positioned at the bottom of tube, has scattered long spiky hairs near its distal end. Spiky hairs are also scattered along lower surface of throat. Corollas are set in a small bell-shaped, medium-green calyx edged with five narrowly-triangular ascending to flaring lobes. Exterior of corolla, calyx and pedicels are densely covered with short, sticky, glandular hairs. Filaments, staminode and style are white, as are the glandular hairs. Anthers produce white pollen.
Photo 5: Large corollas are set in relatively short calyxes rimmed with five narrowly-triangular lobes. Glandular hairs cover exterior of corolla and calyx. A staminode can be seen in flower near photo-center.
Photo 6: Display shows a bud, an open complete flower and a flower with most of corolla removed. Note shape of flower, small calyx, glandular hairs, two-part anthers and straight hairs at distal end of staminode.
With fertilization, ovaries enlarge to form raindrop-shaped capsules that taper to the apex tipped by the drying style. Capsules enlarge to about three times longer than calyx, turning light brown at maturity and splitting from tip to base to release numerous tiny, angular, irregularly ridged, brown seeds.
In a garden or natural area, foxglove beardtongue would stand out due to its height, large widely spaced stem leaves and its showy foxglove-type flowers. Flowers may be present for a month in mid-spring. Timely removal of seed capsules can prevent any undesired self-seeding. Foxglove beardtongue has been listed by the Missouri Prairie Foundation as a “Grow Native!” plant (recommended for home landscapes).
Four other white-blooming beadtongues occur in Arkansas: Arkansas beardtongue (Penstemon arkansanus), nodding beardtongue (Penstemon laxiflorus), pale beardtongue (Penstemon pallidus), and white wand beardtongue (Penstemon tubaeflorus). Foxglove beardtongue can be distinguished by its 1) large size (plant and flowers), 2) glabrous nature, except for its glandular hairs on and near flowers, 3) foxglove-like corollas with lobes that are similarly flared and with similar length, and 4) a staminode that has scattered long straight hairs near its distal end.
Article and photographs by ANPS member Sid Vogelpohl
Photo 1: As plants become dormant, leaves and stem dry and shrink away, leaving only the bulb to persist underground. Photo – early June.
Photo 2: Death camas first appears as an erect rosette of leaves. Photo – late February.
Photo 3: Thick smooth basal leaves, u-shaped in cross-section, are erect to recurved. Cauline leaves have a similar appearance, but have a basal sheath or are clasping. Note exaggerated length of leaves (bracts) just below the inforescence. Photo – late April.
Photo 4: Lowermost flowers are past anthesis while uppermost flowers remain in bud. Pedicels and rachis continue to grow as flowers bloom so that clusters become cylindrical. Photo – early May.
Photo 5: The three outer tepals (sepals) are wider and cupped as compared to the three inner tepals (petals). Flowers have three styles that flare outward as flowers mature.
Photo 6: In late June, plant has become dormant and seed capsules have dried.
Photo 1: In its preferred habitat, a seeded colony stands out.
Photo 2: In early spring, the first leaves are rising from the duff.
Photo 3: Mature plants produce a stem that terminates with the inflorescence. Upper stem leaves, with a broadened base, are sessile and clasping.
Photo 4: This early stem, with inflorescences still crowded, terminates with two divergent scorpioid cymes with a separate lower cyme.
Photo 5: Whitish buds become pale blue as flowers reach anthesis. Note elevated ring around throat and dense appressed pubescence on pedicles and calyx.
Photo 6: Whitish flower buds are nearer distal end of coiled cymes than blue flowers. Ovaries split into four spiky nutlets while style is still present.
Photo 1: In early spring, stems of older multi-stemmed plants grow from perimeter of root clump. Apical clusters of tightly wound pubescent blue flower buds are quickly apparent.
Photo 2: Upper leaves of these main stems subtend floral branches and secondary stems. Note leaf venation and pubescence of tightly wound flower buds.
Photo 3: Flowers are set in tiny calyxes with greenish dilated corolla tubes, as seen on buds at left. Pale blue flowers have a whitish center with radiating hairs. Secondary stems grow from leaf axils below floral branches.
Photo 4: Flowers have tiny calyxes, styles with knob-like stigmas, and anthers on short filaments. Villous pubescence occurs on exterior and interior of floral tube.
Photo 5: With fertilization, the two ovaries of the pistil separate and lengthen into bean-like pods that may be 5 or more inches long
Photo 6: In this early June photo, seed pods are maturing. Brown seed capsules in background are on
Photo 6: In this mid-November photo, leaves are an attractive golden-yellow.
Photo 1: Leaves unfold as peduncles rise. Photo: mid-March.
Photo 2: Some bulbs may produce a vertical icicle-like rhizome. Matted layer of right-center bulb removed to expose light orange scales. Photo: mid-March.
Photo 3: Bulbs may be replaced by a vertical icicle-like rhizome. Photo: late April.
Photo 4: Bulbs produce leaves and inflorescences directly from upper side basal plates within the bulb. The two smaller plants grew from exterior of basal plate and additional bubils remain attached to the large plant.
Photo 5: In late summer, plants may produce a second bloom at which time, leaves are not present. Photo: mid-September.
Photo 6: As seen in this early March photo, a clonal group may produce many umbels. A couple of flowers in an umbel bloom at any one time, as additional umbels rise from the bulbs.
Photo 7: A “pin” morph flower is shown on left (styles longer than stamens) and a “thrum” morph flower is shown on right (styles shorter than stamens). In the inset, shorter pistils can be seen below stamens (thrum morph).
Photo 1: Near-surface rhizomes are smooth and heavily rooted. New growth originates at terminal and lateral buds.
Photo 2: Leaves, occurring singly or in pairs, are orbicular with deep, broadly-open sinuses at the bases.
Photo 3: Single flowers grow from between pairs of leaves. Note pubescence on leaf blades, petioles and calyx. Leaf in upper right corner is a violet. Photo taken April 7th.
Photo 4: The twelve stamens have released their yellow pollen, some of which can be seen on the six stigmas. Six of the now-barren stamens are positioned between pistils (see star pattern) while other six stamens are positioned across stigmas.
Photo 5: After anthesis, stamens and styles shrink and colors fade. Photo taken April 20th.
Photo 6: Fruit capsule has split to discharge mature, smooth, brown seeds with attached elaiosomes. Photo taken May 19th.
Photo 1: New stalks grow upright from tips of new horizontal rhizomes. Photo in early February
Photo 2: Mottling of leaves is strongest when they first expand. In this early March photo, sepals still cover the upright flower buds.
Photo 3: At anthesis, sepals flare horizontally while petals remain mostly upright. Photo taken mid-March.
Photo 4: Display shows one of three leaves (upper center), three sepals (right), three petals (left), six stamens (lower left and right) and the pistil (lower center). Note venation of leaf, sepals and petals.
Photo 5: Immature ovoid fruits are surrounded by persistent sepals and leaves. Plant in background with palmate leaves is tall thimbleweed (Anemone virginiana), a common associate plant in the wild. Photo taken in early May.
Photo 6: Fruit disintegrates to expose smooth, brown seeds with white elaiosomes. Inset shows seeds with elaisomes. Photo in late June.
Photo 1: Main trunks are furrowed while smaller trunk to right is smooth with splotches of lighter color. Lowest portion of central main trunk is 18 inches in circumference.
Photo 2: In this early February photo, imbricated bud scales are elongating as enclosed rudimentary inflorescence and stems develop. Upper surface of two fallen leaves shown on left. Lower surface of leaves shown on right.
Photo 3: In mid-March, flowers of downy serviceberry are in bloom while nearby trees remain dormant. Before the advent of the exotic, invasive Callery pear, serviceberry was the first tree with showy flowers to bloom in the woods, earlier even than the wild plums.
Photo 4: Racemes of flowers that are approaching anthesis. Previous year’s stems are brown to purplish, while older stems are gray.
Photo 5: Pedicels, peduncles, margins of bud scales and pedicellate bracts are woolly. Bud at left shows that the inflorescence is fully developed before the stem (to which inflorescence is attached) becomes evident.
Photo 6: In early May, the fruit cluster is attached opposite a leaf on the lower portion of the new stem. Up-folded leaf blade along midrib, serrated margins and venation can be seen.
Photo 1: This late-January photo shows a single, newly rooted stem that produced a flower spike the previous year (dead stem at upper left). Thereafter, lateral axillary stems developed that will produce apical flower spikes in the current year.
Photo 2: In late January, previous year’s stems (purple) that were elevated were subject to freezing while ground-hugging stems thrived, producing new side stems with fresh leaves.
Photo 3: Lavender flower buds appear from calyxes rimmed with linear tooth-like lobes. Note leaf shape, venation and pubescence as well as glandular pubescent calyx lobes. Photo in mid-March.
Photo 4: Early flowers of two spikes are shown along with a developing spike (upper left center). Flowers have long corolla tubes (see lower flower of upper spike). Leaves of this plant are more elongate than plant in previous photo.
Photo 5: Throats of flowers are covered by a thick fringe of hair so that reproductive parts cannot be seen.
Photo 6: Rose vervain in a sunny rock garden setting. Photo in late March.