foxglove beardtongue (Penstemon digitalis)
foxglove beard tongue
tall white beard-tongue
talus slope penstemon
Penstemon laevigatus ssp. digitalis (Nutt. ex Sims) Bennett
Penstemon laevigatus var. angulatus Bennet
CONFIRMATION STATUS: Pending confirmation.
TAXONOMY: The currently accepted scientific name of foxglove
beardtongue is Penstemon digitalis Nutt. ex Sims. Foxglove beardtongue
can be distinguished from other members of the genus by the absence
of hairs on the leaves and stems, a corolla that is primarily white on the
outer surface (but sometimes with violet tints), the presence of tiny white
hairs on the anthers (resembling small combs), and an absence of ridges
on the lower inner surface of the corolla. The small hairs on the anthers
can lodge against the hairs of a visiting bee, causing the stamens to bend
downward to deposit pollen on the back of the insect, if it is sufficiently
large in size.
NATIVE STATUS: Native, United States; Introduced, Canada.
GENERAL BOTANICAL CHARACTERISTICS:
Habit: One or more flowering stalks, about 3' tall, emerge from clustered
rosettes during the spring.
Leaves: Prior to developing an inflorescence, this native perennial plant
consists of one or more rosettes of basal leaves that are clustered together.
They are medium green, sometimes with reddish tints. They are variable
in shape, but tend to be ovate, obovate, or broadly lanceolate, and are up
to 6" long and 2½" wide. Their margins are usually smooth. They are
hairless and light green, while the opposite leaves on these stalks are more
lanceolate in shape than the basal leaves. Their edges often have tiny teeth,
and the leaf surface is often shiny.
Flowers: The white flowers occur in a panicle at the top of each flowering
stem. They are tubular in shape and about 1" long, with the corolla divided
into a lower lip with 3 lobes and and an upper lip with 2 lobes. Somtimes
there are fine lines of violet within the corolla, which function as nectar
guides to visiting insects. There is no floral scent. The entire plant is hair-
less, except on the outer surface of the flowers.
Fruit/Seeds: The flowering stalk eventually turns dark brown, develop-
ing numerous oval seed capsules, each containing numerous seeds. These
seeds are gray, finely pitted, and irregularly angled. This inflorescence
eventually falls over are the seeds have formed, helping to distribute
them, but the basal leaves remain. The small seeds can also be carried
aloft by the wind for short distances.
Roots: The root system has short rhizomes, which often produce new
plantlets around the base.
REGENERATION PROCESS: Foxglove beardtongue propagates itself
HABITAT TYPES: Habitats include mesic black soil prairies, open-
ings in upland and floodplain forests, woodland borders, thickets, savan-
nas, acid gravel seeps, pastures, and abandoned fields.
SITE CHARACTERISTICS: The preference is full or partial sun,
average levels of moisture, and loamy soil. This plant matures quickly
during the spring, and the flowering stalks often ascend above neigh-
boring plants. It adapts well to cultivation, is not bothered by disease,
and is easy to grow. Under severe drought conditions, however, the
leaves may turn yellow and the plant will wilt.
SEASONAL DEVELOPMENT: Foxglove beardtongue blooms during
late spring or early summer for about a month.
GENERAL DISTRIBUTION: Foxglove beardtongue is naturally found
all parts of the eastern United States (except Florida) and Canada (except-
ing Labrador). It extends into the Ohio Valley, mid-West and the Plains
states, but is not found in the far southwest states, Rocky Mountain states,
or the far west Pacific states.
SKY MEADOWS DISTRIBUTION: To be determined.
IMPORTANCE AND USES: The tubular flowers of this plant attract
long-tongued bees, including honeybees, bumblebees, anthophorine bees,
miner bees, mason bees, and large leaf-cutting bees. To a lesser extent,
halictid bees, butterflies, sphinx moths, and hummingbirds may visit the
flowers, but they are not effective pollinators. The caterpillars of the moth
Elaphria chalcedonia (chalcedony midget) feed on the foliage of this and
other beardtongues. There have been reports that the caterpillars of the
butterfly Euphydryes phaeton (Baltimore) feed on the foliage of various
Beetles and syrphid flies feed on either pollen or stray pollen and are non-
pollinating. Some wasps and the large carpenter bee perforate the flowers,
suck nectar from perforated flowers, and are non-pollinating while the
Penstemon wasp sucks nectar and collects pollen. The seeds are not often
eaten by birds (hummingbirds have been reported sucking nectar), nor is
the foliage an attractive source of food to mammalian herbivores, although
they may browse on it when little else is available.
As an ornamental, foxglove beardtongue is probably the easiest Penstemon
species to grow in areas that lie east of the Mississippi River. The flowers
are quite showy, and the plant is large enough to compete against many
kinds of weeds. Another desirable feature is that the blooming period is
rather long for an early season plant.
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Crooked Run Valley