When the dog days of summer roll around, your garden takes a break from flowering. Thanks to the late breeder Donald Egolf at the U.S. National Arboretum, you can fill this color void with two fabulous dog day bloomers in their new and improved varieties.
Egolf worked hard to breed superior forms of two beloved old plants, shrub althea and crape myrtle. Both are hallmarks of the South, but improved hybrids from the arboretum make it possible to enjoy both just about everywhere.
The single drawback to crape myrtle trees is their vulnerability to mildew, which has limited their use in coastal regions in the past. The disease of the foliage is common where warm temperatures and humidity create an ideal environment for fungus to thrive. Egolf’s 1959 startup program at the arboretum was dedicated to breeding new mildew-resistant varieties, as well as those with more variable size and new flower colors.
Breeding kicked off with seed of L. fauriei, gathered in Yakushima, Japan, by John Creech of the Raulston Arboretum in North Carolina around 1956. This well-known mildew-resistant species also featured improved bark colors for a new appealing characteristic in its progeny. This was the pivotal species for Egolf’s program to transform Lagerstroemia indica into a series of mildew-free hybrids.
A second breakthrough came in 1981 with L. limii, another mildew-resistant species contributed by the Shanghai Botanic Garden to further the genetic potential for problem-solving through breeding.
The crape myrtle breeding program has resulted in scores of hybrid trees and shrubs that offer disease resistance and a range of sizes, growth habits, flower and bark color. You’ll know the arboretum hybrids by their names honoring Native American tribes such as Sioux and Chickasaw.
Egolf was also interested in Hibiscus syriacus, an old-fashioned deciduous flowering shrub native to southeast Asia that became a Texas heirloom. It’s fondly known as shrub althea. Egolf utilized state-of-the-art technology to breed triploid hybrids, which contain three times the usual number of chromosomes. This proportionately increases the potential for new characteristics that would have been impossible in the past.
Among Egolf’s goals with the hibiscus was to maximize drought resistance, reduce the size of the species to a more versatile shrub, increase flower production, extend the season of bloom and create exciting flower colors. These outstanding hybrids are named for mythological goddesses such as Aphrodite or Diana.
With the current drought and nationwide demands for water conservation, Egolf’s triploid althea hybrids developed in the 1960s are suddenly highly valued for drought-resistant landscaping. What makes them so important is cold hardiness. Too many arid zone plants hailing from mild winters of Australia and the Mediterranean are restricted to very warm winter climates. But these hibiscus goddesses take winters in Zone 5, 100-degree days, minimal water and virtually any kind of soil. This is a rare heavy bloomer for dry gardens in western mountains and colder inland regions.
To learn more about both these groups of U.S. National Arboretum plant introductions, go to usna.usda.gov to access full color printable fact sheets for all their plants. These give details to help you select the right one for the space or create the look you have in mind. Print them and keep on hand when you go shopping at the garden center, or use to aid in special ordering if the plants are not in stock.
To bring color into a late summer garden, choose from these old-fashioned favorites re-created for modern times. They are the legacy of a brilliant plant breeder who deserves more recognition outside of horticul-
tural circles because his creations make our nation’s landscapes and cityscapes stunningly beautiful.
Get a traditional look and romantic sense of place by lighting up the garden at summer’s end without having to worry about disease, heat, cold or drought.