Foxglove Beard Tongue
Penstemon digitalis
Snapdragon family
Click on an image for a higher resolution photograph.
All photos taken at the Klein Prairie -- Murrayville, Illinois, USA
Description:
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. One or more flowering stalks emerge from the
clustered rosettes during the spring, which are about 3' tall. 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. The white flowers occur in a panicle at the top of each
flowering stem, and bloom during late spring or early summer for about a month.
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. Sometimes 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 hairless, except
on the outer surface of the flowers. The flowering stalk eventually turns dark
brown, developing 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. The root system has short rhizomes, which often produce new
plantlets around the base.
Cultivation: 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
neighboring 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.
Range & Habitat: Foxglove Penstemon occurs
occasionally, except in some counties of central and NW Illinois, where it is
uncommon or absent (see
Distribution Map). However, in other areas, it may be locally common.
Habitats include mesic black soil prairies, openings in upland and floodplain
forests, woodland borders, thickets, savannas, acid gravel seeps, pastures, and
abandoned fields.
Faunal Associations: 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 beardtongues, but this does not appear to be the case in Illinois. The
seeds are not often eaten by birds, nor is the foliage an attractive source of
food to mammalian herbivores, although they may browse on it when little else is
available.
Comments: This is probably the easiest
Penstemon sp. 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. Foxglove Penstemon 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.
Source: http://www.illinoiswildflowers.info
The text above is Copyright © 2002-2005 by John Hilty. All photography on this site is © 2005, 2007 by Kevin Klein. Photo quality prints and permission for image use may be obtained by contacting the photographer at kklein@ic.edu.
