Date of this Version
HORTSCIENCE 44(3):839–840. 2009
Penstemon Mitch. (Plantaginaceae Juss. formerly Scrophulariaceae Juss.) is a diverse genus of ≈271 species that occur throughout the United States (except Hawaii), Canada, Mexico, and Guatemala (Lindgren and Wilde, 2003). Many cultivars have been named (Lindgren, 2006). Although selections from interspecific crosses are less common than intraspecific crosses, many European hybrids have been derived from intercrossing species and hybrids from Mexico with the large flowered P. cobaea Nutt. from the central United States. Most of these large and colorfully flowered European hybrids do not overwinter in the United States except in the milder climates.
Selections from intersectional crosses between the Sect. Fasciculus Keck ex Straw and the Sect. Peltanthera Keck of Penstemon have resulted in a group of plants known as the Mexicana complex, which is a hybrid population. This complex displays intermediate characteristics between the parents. In 1980, the first of the Mexicali complex was established by introducing the large-flowered variety called ‘Sensation’ into the Mexicana complex. Plants from the Mexicali complex are believed to have received their winterhardiness and long bloom from the Penstemon Section Fasciculus and larger flowers from the Penstemon Section Peltanthera and the variety ‘Sensation’ (Meyers, 1998). Meyers produced four Mexicali lines. One line resembled the Section Peltanthera parents, one line resembled the ‘Sensation’ parent, and two lines resembled the Section Fasciculus parents.
Seeds of the Mexicali complex were distributed to members of the American Penstemon Society (APS) through the APS seed exchange, and the resultant seedlings of some of these Mexicali selections performed well. Red Rocks™, Pikes Peak Purple™, and Shadow Mountain™ are three selections from the Mexicali complex made in Colorado and released through the Plant Select® plants program. Other selections from the Mexicali complex have been made as well (Lindgren, 2006). Some plants in this group possess fascicles. Fascicles are secondary branches that grow out and produce flowers later in the season, which extends the flowering season (Way and James, 1998). New Penstemon selections with large flowers, cold-hardiness, longevity, adaptation to a range of growing conditions, and an extended flowering season are needed. ‘Sweet Joanne’ meets these requirements.