Sorting Out the Azalea Groups
Reprinted from the Valley Forge newsletter August 1996
When I was new to the Society, I was puzzled, overwhelmed, and intimidated by some of the terms used by "old hands." Using various resources, but especially Fred Galle's Azaleas, I started for my own enlightenment a list of the major groups of azaleas frequently identified by the name of the hybridizer or by some other affiliation. The list, which is by no means complete, is shared with others who are new to the subject.
Gable hybrids: Joseph Gable of Stewartstown, Pennsylvania, introduced some of the hardiest evergreen azaleas and rhododendrons. Most of his azaleas are of medium height (6-8 inches). An extensive list of the highly regarded Gable hybrids, rhododendrons and azaleas, can be found in the chapter's January 1994 newsletter.
Linwood azaleas: Charles Fisher, Jr., of Linwood, New Jersey, started in 1950 to develop hardy evergreen azaleas, a project taken over in 1953 by Al Reid. 'Hardy Gardenia', which does look like a gardenia, is one of the hardy azaleas with good plant habit, foliage, and flower quality that were developed.
Hershey azaleas: These come from the Hershey Azalea farm in Cap, Pennsylvania, started in 1936 by the late Ralph Hershey and continued by his son. Most of these evergreen azaleas are Kurume hybrids. Their exact parentage is unknown.
Kurume hybrids: Kurume, a city on the Japanese island of Kyushu, is home to this large group of hybrids, believed to be derived from evergreen azalea species in the southern part of the island.
Beltsville (Yerkes-Pryor) hybrids: The Horticultural Crops Research Division of the U.S. Department of Agriculture in Beltsville introduced evergreen azaleas in the 1950s. These plants were hybridized for hardiness.
Shammarello hybrids: These hybrids were introduced by the late Tony Shammarello of South Euclid, Ohio, and are hardy to -15°F.
Robin Hill hybrids: Robert Gartrell of Wyckoff, New Jersey, started in 1937 to produce hardy and late-blooming evergreen azaleas with flowers comparable to those of Satsuki hybrids. They bloom in our area from mid-May to early June. Most are 3-5 feet in height. Among them, 'Nancy of Robinhill', is probably the best known.
Glenn Dale hybrids: Hybridizing was started in the 1930s by B. (Ben) Y. Morrison, horticulturist and Chief of Plant Introduction Section at the National Arboretum, USDA. These hybrids take their name from the location of the plant introduction station at Glenn Dale, Maryland. Morrison concentrated on cold-hardy plants with large flowers that bloom from mid-April to mid-June. 'Ben Morrison' is a beautiful bi-color that was named in his memory.
Weston hybrids: After a killing winter (1933), Ed Mezitt of Weston Nurseries in Hopkinton, Massachusetts, started selecting and breeding azaleas hardy to -25°F. However, Weston Nurseries is probably best known for some of the hardiest small-leaf rhododendron hybrids, such as the PJM Group, which flowers early and has beautiful winter foliage.
Knap Hill hybrids: In 1870, Anthony Waterer and his son of Knap Hill, England, started to cross Ghent azaleas with Chinese azaleas and other species. Their deciduous hybrids are generally medium high or large shrubs (4-10 feet high and 4-6 feet wide). The flowers are large, and many are fragrant. Fall foliage is excellent.
Satsuki azaleas: They are the most popular in Japan. Their range of flower color, form, leaf shape, and growth habit is greater than that of any other group of azaleas. Their development is shrouded in mystery, but at least one cultivar is known to be 400 to 500 years old. They usually bloom from mid-May to June and have single flowers that range in size from less than 1 inch to over 5 inches. Ben Morrison (see Beltsville hybrids) used Satsuki azaleas as parents for many Glenn Dale hybrids, and so did Robert Gartrell for his Robin Hill hybrids.
Kaempferi hybrids: cultivars have R. kaempferi as a parent. Prof. C.S. Sargent of the Arnold Arboretum introduced R. kaempferi to the United States from seed collected in Japan and sent seed to Kew Gardens in England in the 1890s. Hybrids were developed in Holland during World War I by P.M. Koster, who later left Holland and established a nursery in New Jersey. Kaempferi hybrid evergreen azaleas are very hardy in the northeastern and midwestern United States. Joseph Gable (see Gable hybrids) and others used R. kaempferi for their hybrids.
Girard hybrids: Peter Girard of Geneva, Ohio, hybridized for resistance against mildew and heat and used mainly Knap Hill hybrids. Many of his deciduous hybrids are doubles with a wide range of colors and have good fall foliage. Girard started hybridizing evergreen azaleas with Gable hybrids and then crossed his own seedlings and named hybrids. His plants are hardy and of medium size (4-6 feet).
There are many other groups of rhododendrons and evergreen and deciduous azaleas, such as Exbury azaleas introduced by Lionel de Rothschild of Exbury, England, and Mollis deciduous azalea hybrids derived mainly from R. japonicum.