Culture
Easily grown in average, dry to medium, well-drained soils in full sun. Plants have some tolerance for drought, summer heat and humidity. Avoid wet, poorly-drained soils. Remove spent flowering racemes to prolong bloom. Plants may be cut back to basal foliage after flowering to improve appearance of the planting. Plants in cold winter climates often benefit from a loose winter mulch.
Noteworthy Characteristics
Penstemon is a genus of about 250 species of herbaceous perennials and sub-shrubs which are primarily native to the continental U.S., Canada, Mexico and Guatemala in a variety of habitats ranging from desert to plains to alpine slopes. A large number of hybrids have been developed over the years, but most are of unclear parentage.
The genus name Penstemon likely comes from the Latin paene meaning "almost" or "nearly" and the Greek stemon meaning "stamen". The name may also comes from the Greek penta meaning "five" and stemon meaning "stamen". Both refer to the fifth, sterile stamen (staminode) that characterizes members of this genus.
Penstemons are sometimes commonly called beardtongues because the sterile stamen (staminode) can be hairy.
‘Dark Towers’ is a clump-forming penstemon that typically grows 1.5-3’ tall. It is noted for its pink flowers and dark wine-red foliage. Two-lipped, tubular, pale pink flowers (each to 1.5”) in loose terminal racemes bloom from late spring into summer atop erect, rigid, leafy stems. Foliage (oblong to ovate basal leaves and lance-shaped stem leaves) are an attractive dark maroon/wine red. Foliage generally retains good color throughout summer. 'Dark Towers' is similar to Penstemon digitalis 'Husker Red', but differs by having darker red foliage that appears to maintain its dark red color better in summer, pink instead of white flowers and slightly taller plant height. Both cultivars were developed and introduced by Dale Lindgren at the University of Nebraska.
Problems
Root rot can occur in wet, poorly-drained soils. Leaf spots, rusts, powdery mildew and Southern blight may also occur. Slugs and snails may chew on the foliage. Watch for spider mites. Deer tend to avoid this plant.
Uses
Sunny areas of borders, rock gardens, cottage gardens and open woodland areas.