Source: JARS V48:No.1:p73:y1994
R. prunifolium and Its Children
The flowering season for many rhododendrons and azaleas is completed by June, but there are other varieties available to extend the blooming period even into September. Many of these late bloomers are derived from the plumleaf azalea, Rhododendron prunifolium.
Rhododendron prunifolium, a native deciduous plant of Georgia and Alabama, grows into a large shrub, often attaining a height of 15 feet in the wild. The orange to orange-red or even red flowers, appearing in July and August, have a tubular shape with graceful long stamens. They stand out in bright profusion against the dark green foliage. The flower buds are usually striped in appearance. Even with its southern heritage, R. prunifolium has proven to be completely hardy and a "good doer" on Long Island, and certain clones have demonstrated hardiness to -20°F. A semi-shady planting site is recommended to preserve the flowers, especially during the heat of summer.
There are several selections of the species which include the following: "Summer Sunset" selected by the Crown Estate Commissioners, Windsor, with vivid red flowers; 'Hohman' chosen by Hohman for its deep reddish-orange flowers; and 'S. D. Coleman' selected by David Leach and enhanced by vibrant reddish-orange flowers.
Several hybridizers have tried to lengthen and extend the flowering time by using R. prunifolium as a parent. It has proven to be surprisingly hardy as well as a good parent. David Leach, while at North Madison, Ohio, made several crosses utilizing the 'S. D. Coleman' form of R. prunifolium to extend the blooming season. Among his July Series are 'July Jester' (R. prunifolium 'S. D. Coleman' x R. bakeri 'Scarlet Salute') with vivid reddish-orange flowers and a medium height; 'July Jewel' (R. prunifolium 'S. D. Coleman' x R. bakeri 'Scarlet Salute') showing a deep reddish-orange color and semi-dwarf habit, and 'July Jubilation' (R. prunifolium 'S. D. Coleman' x 'Cream Puff') another semi-dwarf with strong reddish-orange flowers.
Weston Nurseries of Massachusetts had an ambitious hybridizing program for summer blooming azaleas. It was begun in the 1930s by Edmund Mezitt and is carried on today by his son Wayne. Among their R. prunifolium hybrids are: 'Cherry Bomb', a July bloomer with large cherry red flowers; 'Tangerine Glow' bringing a show of dark orange flowers from July into August; 'Everglow' with dark orange-red flowers from July into August; and 'Pennsylvania' blooming in July with light pink flowers.
Jim Cross of Environmentals on Long Island has just recently introduced a wonderful new hybrid called 'Sweet September'. The plant blooms reliably in mid-September with clear pink flowers and red stamens. It has an upright habit.
Roslyn Nursery of Dix Hills plans to release in 1995 a new September blooming form of R. prunifolium with large orange-red flowers. The plant has bloomed profusely on Long Island for the past six years, and it is an attractive shrub year round.
These plants will become more popular in the future as the public realizes their exciting possibilities. The late bloomers offer bright colors when many people are spending more time in the outdoors. These azaleas are easy to grow, reliably hardy, shade tolerant, and have attractive foliage. They should have a place in every garden, especially those of ARS members