Perennial Notes Excerpts
Regular contributor, and former GPPA President, Paula Refi, showed great foresight in writing about Penstemon digitalis back in Spring of 1994. This plant became the 1996 Perennial Plant of the Year, as selected by the Perennial Plant Association. Paula assisted in updating this article which first appeared in the Spring 1994 issue of Perennial Notes.
THE PERENNIAL SEARCH
It's difficult enough when an admirable plant has an unfamiliar Latin epithet. It's worse when that plant is also burdened with an off-putting common name. And its humble status as a southeastern native wildflower means that foxglove beardtongue (Penstemon digitalis) languishes in relative obscurity and is rarely cultivated in perennial gardens. Recently, however, the selection of Penstemon 'Husker Red' at the University of Nebraska, a form that displays distinctive burgundy stems and foliage, has legitimized the plant and earned it a listing in several respected mail-order catalogs. Favorable reviews awarded to this aristocratic offspring have resulted in better press for the species.
Penstemon comes from two Greek words, 'pente' meaning five and 'stemon' meaning stamen. Together, they describe the flower's five stamens. Four of these are fertile. The sterile fifth one is hairy and gives the plant its common name of beardtongue. Digitalis refers to its foxglove cousin in the family Scrophulariaceae.
The flowering stem can rise to 36 inches above the basal foliage, and it bears a spike or raceme of many tubular white flowers with pink or light purple veins. Typical of the family of "Scrophs", five petals fuse to create the floral tube. Two of the petals are above and three are below. The blossom's lower throat is also hairy.
A few minutes of close inspection with a hand lens can leave one awestruck by the delicate beauty of Penstemon digitalis. The corolla is small enough, at two or three centimeters, that the effect of the inflorescence is soft and upright. It wafts and leans even in full sun, without the necessity for staking. The blooms appear in May and June.
In the wild, P. digitalis is a plant of roadsides and old fields. It is often found in places with poor drainage. The plant's adaptive character has been proven in recent years at the Georgia Perimeter College Botanical College, where George Sanko has put it through its paces in several locations. After two years, in full sun and without amending the soil, Sanko reports superb bloom and vigor. Clumps are big enough to divide in the third year. In a partly shaded bed enriched with compost, he observed comparable performance. In total shade, the blooms were less showy, as one would expect. Volunteer seedlings sometimes appear, and Sanko finds germination rates approaching 100% when freshly harvested seed is sown in the greenhouse.
Such a vigorous perennial deserves better exposure in our gardens. With its versatile white blossoms, it would enhance blue or purple companions, such as Siberian iris (Iris siberica) or columbine (Aquilegia canadensis). Or try stretching foxglove beardtongue to its shaded limit with pink astilbe (Astilbe x arendsii).
After four seasons in my garden, Penstemon digitalis 'Husker Red' grows just as well as the species. Its burgundy stems and red-tinged leaves are nearly as ornamental as the blooms, and they are much appreciated against the silver-gray foliage of nearby artemisia. It is available at many local nurseries and mail-order perennial sources.
This photo appears with the permission of Bluestone Perennials, Inc. and is borrowed from their online catalog at www.bluestoneperennials.com.