Penstemon (Bearded Tongue) is a wonderful but underappreciated perennial. It may be finicky about drainage but it’s well worth the effort of amending your soil.
One of the easiest to raise is P.digitalis and its cultivars. The best known of these is ‘Husker Red’ which features darker foliage than the species but retains the white flowers. For the past few years, I’ve been growing two other cultivars, ‘Dark Towers’ and ‘Pocahontas’, that I prefer. I find it difficult to tell them apart even though I grow them side by side. The foliage is even darker than that of ‘Husker Red’ and the flowers are a pale lavender pink. They probably grow twenty-four inches high instead of eighteen inches. The tubular flowers last for about a month and the dark foliage provides contrast for the rest of the summer to all of the green foliage in the garden and to the bi-colored foliage of an unknown Sedum.
I also grow P.tubaeflorus, a Missouri native that occurs in dryish soils. In my garden, it grows three feet tall and has seeded a little bit. Its white clusters of trumpets sit at the toop of rigid stems. It flowers at the same time as ‘Dark Towers’ in the same bed with intervening perennials so that the repetition of form is a welcome sight. The foliage is narrower than that of ‘Dark Towers’ and is green.
Totally different is P.barbatus, a native of the Southwest. I first saw it in Arizona. The bright reddish-orange flowers stay in bloom for a very long time. They make quite a show in June and July. Then I cut them back and they rebloom in August and September. Although technically, this Penstemon is eighteen to thirty-six inches high, the stems are quite lax resulting in a height of approximately twelve to eighteen inches. Perfect drainage is essential for this species. You, too, can achieve this by purchasing Turface, an enlarged aggregate, at a garden center. Dig copious amounts of it into your soil so that the roots do not stay wet during the winter. The effort will be well worth it.