About Penstemon digitalis Nutt.
Penstemon digitalis Nutt. is a glabrous herbaceous plant, growing between 3 and 5 feet tall, with slender purple stems and opposite, simple, shiny green leaves. Its leaves reach up to 5 inches long; basal leaves are elliptic, while stem leaves are lance-shaped to oblong. Most upright stems average 2 to 3 feet in height. The flowering panicle extends to almost one-third of the plant's total height, and bears repeated pairs of branches that each produce two flowers. The pedicels are almost one-quarter of an inch long, and produce 1.25-inch long two-lipped tubular flowers that sit above dark green foliage. The outer surface of the flower tube has tiny white hairs. The species was originally described as "Fox-Glove-Like Pentstemon" (sic), and its specific epithet digitalis directly references the foxglove genus Digitalis. This plant grows in moist, sandy soil in full sun, found in meadows, prairies, fields, wood margins, open woods, and along railroad tracks. It blooms from late spring to early summer, attracts butterflies, bees, and birds including hummingbirds, and tolerates deer browsing. Its natural native range is in the central United States, centered largely on the Mississippi River watershed. It extends southwest into Texas, east into Alabama, and north into Michigan. It has become naturalized across eastern United States and Canada, ranging from South Carolina up the eastern seaboard to Ontario and Québec. Like other Penstemon species, it is used for roadside plantings because it is easy to grow and has showy blooms. The American Penstemon Society recommends it for easy garden use from the Midwest to the Atlantic coast and Pacific Northwest. Iowa's Living Roadway Profiler, a project of the Iowa Department of Transportation, notes that the plant's decorative seed capsules add visual interest during fall and winter. One popular cultivar of this species is 'Husker Red', named for its red foliage, and it bears white or bluish-pink flowers. The Perennial Plant Association selected Penstemon digitalis 'Husker Red' as the 1996 Perennial Plant of the Year. The author of the book Perennial All-Stars described 'Husker Red' as "a stunning flowering perennial" and noted that "you can easily see why the Perennial Plant Association chose this perennial above all others". This cultivar was named after the Nebraska Cornhuskers. A second cultivar, 'Mystica', has green foliage when young that changes to red in the fall. Penstemon 'Dark Towers' is a hybrid cross between Penstemon digitalis 'Husker Red' and Penstemon 'Prairie Splendor'—itself a hybrid of Penstemon cobaea and Penstemon triflorus. This hybrid grows 1.5 to 3 feet tall, has red foliage, and produces tubular pink flowers that reach up to 1.5 inches long. While similar to 'Husker Red', 'Dark Towers' has darker red foliage, greater overall height, and retains its red color for a longer period through the summer. Dale Lindgren created and named both 'Husker Red' and 'Dark Towers' at the University of Nebraska–Lincoln, with 'Husker Red' originating in 1983. Lindgren developed 'Husker Red' specifically for its purplish-red foliage.
