Cobaea beardtongue, or purple beardtongue, is probably Missouri’s showiest species of penstemon. The flowers may be purple or white. A perennial wildflower with upright stalks, sometimes from a spreading base, the plant is densely covered with glandular hairs.
The stem leaves are opposite, clasping, with a heavy midrib, sharply toothed, 1–6 inches long, the lower leaves reverse-lance-shaped to narrowly oblong-elliptic; higher up, they gradually become lance-shaped to ovate, with sharply pointed tips. The upper surfaces of the leaves usually appear glossy from a distance. The basal leaves may be spoon-shaped, with a winged leaf stem.
The flowers are in panicles at the tops of the plant and resemble snapdragons, with the 2-lobed upper lip spreading or else curving forward somewhat, and the 3-lobed lower lip spreading to somewhat bent backward. The floral tube is enlarged and looks inflated. The flowers may be white or purple, or (rarely) pink or light purple. When purple, they sometimes have a white ring at the base of the petal lobes. The throat is lined with darker reddish-purple nectar guides and is noticeably ridged on the lower side. Like other penstemons, they have 4 fertile stamens (which produce viable pollen and curl up along the sides of the floral tube) and 1 infertile stamen (called a staminode), which is white, extends outward toward the floral opening, is flattened toward the tip, and bears numerous hairs on its upper surface. Blooms April–June.
The seed capsules are oval, 4-valved with a pointed tip, positioned upright against the stem, about ½ inch long, and hold small, black-ridged seeds.
The purple-flowering strains of this species have sometimes been treated as a distinct variety, var. purpureus, but because few other characters are different, that special designation seems unwarranted.
Similar species: This is one of 7 species of Penstemon that are native to Missouri. It’s the only one that can have such vivid purple flowers. Note that white-flowering forms of cobaea penstemon might be confused with large-flowered penstemon (P. grandiflorus). Large-flowered penstemon, however, has strongly glaucous (whitish-waxy-coated) stems and leaves.
Height: 8–30 inches.
Uncommon to scattered in the southern portion of the Missouri’s Ozarks, with a disjunct population in Bates County (on our western border, south of Kansas City). Introduced elsewhere in the state.
Habitat and Conservation
In its native Missouri habitat, in the southern part of the Ozarks, it occurs on limestone and dolomite glades and rock outcrops, and on roadsides.
Because it’s arguably Missouri’s showiest penstemon, and it thrives in dry, rocky, sunny situations, it has been growing in popularity as a landscaping plant. You may see it growing along highways thanks to roadside beautification and native plant projects. You can purchase young plants or seeds at reputable Missouri wildflower nurseries.
Missouri populations of this species are on the eastern edge of the distribution of this species. The overall range is to our west, stretching from Nebraska to Texas, and east to Iowa and Arkansas. As noted above, the flowers may be white or purple. Because people have long cultivated the purple-flowering plants in their gardens, and those plants have sometimes escaped into nature, gardeners may have helped to expand the range of the purple-flowering form.
Status
Showy wildflower native to portions of southern Missouri. Endemic to the central United States. Introduced statewide. The purple form is especially popular in native wildflower gardening and in native roadside plantings.
Human Connections
This species is growing in popularity as a native plant for landscaping. It is a great choice for sunny areas such as rock gardens, borders, and for naturalizing in more natural settings. It is attractive to bees and other pollinators. It is also popular as a beautiful roadside wildflower. It forms clumps and thrives on average, well-drained soils in full sun. If you are interested in growing it, purchase starts or seeds from a reputable wildflower nursery. Missouri primrose, which blooms about the same time and has large, butter-yellow flowers, is a great companion.
Apparently, one drawback of growing penstemons in a garden is that as perennials, they tend to be rather short-lived and usually must reseed themselves to remain present in a garden for more than a few years.
The name “cobaea” references the unrelated genus Cobaea, a group of plants in the phlox family. One of its members in particular, C. scandens, has flowers that closely resemble those of cobaea beardtongue; its bell-shaped flowers have flaring lobes and are the same shade of purple, with white streaks in the throat. A native of Mexico, C. scandens is also called cup-and-saucer vine, cathedral bells, or Mexican ivy. You might have seen it as a landscaping plant. The name Cobaea (the genus of the Mexican plant) honors Padre Bernabé Cobo (1582–1657), a Spanish Jesuit missionary and writer who spent decades living in Latin America. He studied plants as well as human cultures, and he helped bring global attention to the bark of the cinchona tree, which contains quinine and was used to treat malaria. So, this penstemon species indirectly honors Padre Cobo.
Pronunciation: usually, the plant name cobaea is pronounced “ko-BEE-ah.” Latin words are pronounced differently in different contexts. In botanical Latin, the “ae” vowel combination usually is pronounced like “ee,” though in the Catholic Church, “ae” would usually be pronounced “ay,” rhyming with say. Romans a few thousand years ago probably pronounced it “aye,” rhyming with sky.
Cobaea penstemon is said to be a nutritious and palatable forb in livestock pastures. It tends to disappear on overgrazed lands.
The name “penstemon” refers to the unusual fifth stamen that’s characteristic of the genus (pen deriving from Greek penta-, meaning “five”). The name “beardtongue” also refers to the flowers’ infertile but conspicuous, hairy fifth stamen.
Ecosystem Connections
The flowers are attractive to several types of pollinating insects, including bumblebees, moths, and butterflies. The deep purple stripes help guide pollinators into the flower where they are rewarded with nectar as they transfer pollen from one plant to another. The flower’s design encourages (or even forces) a visiting bee to squeeze itself deep into the floral tube. As it wiggles around inside the flower, it presses against the stamens and rubs pollen onto its body. While this is going on, the bee rubs against the flower’s stigma, depositing a previous penstemon’s pollen into it and thus cross-pollinating the flower.
Moths visit the flowers, too, and so do butterflies and a wide variety of bees. Other visitors include certain types of bee flies, the dark flower scarab (also called the spangled flower beetle, Euphoria sepulcralis), and the penstemon wasp (Pseudomasaris occidentalis), whose only food plants are penstemons.
Hummingbirds may also visit the flowers. Reports vary as to the importance of the seeds as food for birds and mammals.
The Baltimore checkerspot (Euphydryas phaeton) and chalcedony midget (Elaphria chalcedonia, a type of noctuid or owlet moth) both use species of penstemons as larval food plants, and they probably use this species as well.
There are about 285 species in genus Penstemon, and this group of colorful wildflowers occurs almost entirely in North America. The greatest diversity is in the Intermountain Region of the western United States, and many of the species are narrow endemics (native to and occurring in a relatively small area). Utah is the center of diversity for the genus, with some 78 different species in various special habitats. In addition to the many natural species in the genus, there are numerous hybrid cultivars developed by gardeners.
