Date of this Version
HORTSCIENCE 44(3):852–853. 2009
Penstemon Mitch. (Plantaginaceae Juss. formerly Scrophulariaceae Juss.) is a genus of plants with ≈ 271 species that can be found from low deserts to high alpine areas (Lindgren and Wilde, 2003; Wolfe et al., 2006). It is one of the largest genera of North American wildflowers. Some Penstemon are easy to grow; others are very challenging to maintain (Lindgren and Wilde, 2003). Numerous selections of Penstemon have been named and released (Lindgren, 2006) and many crosses between species have been attempted (Lindgren and Schaaf, 2007). New Penstemon selections are needed that combine valuable traits of multiple species and cultivars. Several nurseries have also expressed the desire to have a plant similar to Penstemon digitalis Nutt. ‘Husker Red’ only with purple and/or red flowers instead of white flowers.
A cross was made in 1995 between Penstemon digitalis Nutt. ‘Husker Red’ (Lindgren, 1984) with the pollen parent Penstemon ‘Prairie Splendor’ (Penstemon cobaea Nutt. ×Penstemon triflorus A. Heller) (Lindgren, 1993). Three selections were made in 1997 out of the resultant population of seedlings, DM1, DM2, and DM3. All three selections displayed darker fall foliage color than the parent ‘Husker Red’ and were more similar in appearance to ‘Husker Red’ than ‘Prairie Splendor’. The plants were evaluated in field plots until 2003. In 2004, plants of the three selections were evaluated in an additional site at Canby, OR. Selection DM1 was selected and given the cultivar name ‘Dark Towers’. The name ‘Dark Towers’ was selected because after flowering is complete, the flower stalks have dark stems and seed pods, darker than Penstemon ‘Husker Red’. The flowers of ‘Dark Towers’ are pink–lavender rather than white as found in ‘Husker Red’. A comparison of traits of the parents, ‘Husker Red’ and ‘Prairie Splendor’, with ‘Dark Towers’ is found in Table 1.