Smooth beardtongue, calico beardtongue
Zones 4 to 8
24 to 30 inches
Adaptable native plant, excellent in the landscape and in rain gardens
Variable pale pink to purple flowers. The bright green, pointed foliage remains attractive throughout the season, sometimes tinged with red when grown in full sun
Many native denizens of our woodlands and prairies with great ornamental potential have been largely ignored in horticulture. This seems to be the case with the common native Penstemon calycosus. I first encountered this lovely species a couple of decades ago along a woodland stream just a short walk from my home. There, its attractive lavender flowers stood out among the assorted floodplain vegetation. Under a canopy of green ash and sycamore, it grew with green-headed coneflower (Rudbeckia laciniata), burr sedge (Carex grayi) and pagoda dogwood (Cornus alternifolia). Handsome stands of this hardy plant are often seen along woodland edges and stream terraces here in central Indiana.
While the large genus Penstemon reaches peak diversity in the western United States, there are about a dozen species native east of the Mississippi River. Most of us in the nursery trade are familiar with Penstemon digitalis (foxglove beardtongue) and its common selection ‘Husker’s Red’ with its distinctive white flowers and red foliage. Penstemon calycosus (smooth beardtongue) is similar in form but with excitingly variable pale pink to purple flowers. While some individuals sport pale lavender to pink flowers, others are a rich violet. Unfortunately, this beautiful species has remained almost unknown in the nursery trade. Native to most states east of the Mississippi River and hardy to Zones 4 to 8, it was first described by botanists in the late 1800s.
Blooming in late May and early June, it is a beautiful addition to perennial borders. It is very adaptable to most soil types, performing best in loamy soils, but adapting to disturbed soil profiles in developed areas. It typically occurs in neutral soils in its native habitat.
Courtesy of Kevin Tungesvick
Penstemon calycosus is tolerant of both periods of saturation and drought. While it performs well in the dappled shade of open woodland, full sun intensifies the flower color. The bright green, pointed foliage remains attractive throughout the season, sometimes tinged with red when grown in full sun. Usually reaching about 24 inches in height, mature clumps will be up to a foot wide.
Due to its wide tolerance of soil moisture, Penstemon calycosus is an excellent plant for rain gardens. In a rain garden, it will tolerate standing water for up to 24 hours after a rain event. Native species with similar tolerance that make effective companions include pink turtlehead (Chelone oblique), bottle gentian (Gentiana andrewsii), mountain mint (Pycnanthemum virginianum), and obedient plant (Physostegia virginiana).
Penstemon calycosus is also attractive in mass plantings in the landscape. The pleasantly variable flower color adds interest to such plantings. The plants are proving long-lived in the field, with no noticeable decline in our seed production plots after 6 years. Like other Penstemon species, it is easily propagated by seed. It is not especially susceptible to pests or diseases.
Maintenance of this plant in minimal. It may be deadheaded in early summer if seed development is unwanted. As is the case with other penstemons, the ripe seed has an unpleasant odor that can be quite noticeable after a rain. Otherwise, care is limited to removing the previous year’s stems and foliage. The crown is superficial, so take care to cut them back at least 2 inches above soil level.
Other than minor fungal leaf spots, this plant has been largely free of pests and diseases at our nursery and in nearby native stands.
I heartily recommend this beautiful and adaptable species for commercial landscaping, storm water bio-retention, or a residential perennial border. The late-spring blooming period provides color during a period when most spring flowers are finished and summer blooming species have yet to open. The clean foliage is attractive throughout the season. Its adaptability to varying moisture levels makes it ideal for rain gardens. The unusually variable flower color provides interest in the landscape and may lend itself to production of named cultivars in the future. Penstemon calycosus definitely deserves a place in our perennial gardens and commercial landscapes.
Spence Restoration Nursery, Muncie, Ind.