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Species In Our Midst
Rhododendron flammeum

by Sally Perkins


Rhododendron flammeum 'Hazel Hamilton'
Picture by S & J Perkins
Rhododendron flammeum 'Hazel Hamilton' in Salem, NH


Rhododendron flammeum

Rhododendron flammeum (Michx.) Sargent is a deciduous azalea, commonly called the Oconee azalea. It is incorrectly but formerly known as Rhododendron speciosum. The exact date of Western discovery for R. flammeum is not known, but it was in cultivation in Britain in 1789 and was probably sent there by William Bartram prior to that date.

Native to the upland woods, dry slopes, sandhills and bluffs of stream banks in the Piedmont region of Georgia and South Carolina it blooms in April before or with the expansion of its leaves. The scarlet, reddish orange to orange flowers are typically 6-11 in a inflorescence. Although the color range from yellowish-orange to red is variable an orange blotch is typical. Large flower clusters or "ball trusses" is a desirable horticultural trait resulting from multiple terminal flower buds and depend on the health and vigor of the plant. The corolla tube abruptly expands to 5 lobes 1 1/4 to 1 3/4 inches across. The tube is longer than the lobes and is sparsely covered with hairs but has no well-defined glands. The lack of glands is an important identifying feature for this species. The floral bud-scales also have short hairs along their margins but no glands, again an important feature. The long stamens and the longer pistil that extend well beyond the throat give the inflorescence a spidery appearance.

This species is a heat tolerant, low to tall shrub up to 8 feet (2.5 m). It is also considered to be relatively drought tolerant for a deciduous azalea. Breeding programs have incorporated R. flammeum for its color and heat tolerance. It is difficult to root from softwood cuttings and therefore seed propagation and tissue culture has been used. It is not commonly grown in New England but being hardy in USDA zone 6 should be tried. We have grown and bloomed the yellow selection R. flammeum 'Hazel Hamilton' since 1993 in partial shade but is very slow growing for us. Selections include:

  • 'Lemon Popsickle' (Carlson)
  • 'Orange Popsickle' (Carlson)
  • 'Party Girl'
  • 'Hazel Hamilton'

A natural hybrid of R. flammeum with R. canescens called R. x fastigifolium is fragrant ranging in colors of pale yellow to deep pinks. Other hybrids are 'Daty's Plum' and 'Kelly's Orange' hybrids from Fred Galle and 'Cherokee Sunrise' from Joe Parks.

Sources:

Kron, K.A. (1993). A revision of Rhododendron section Pentanthera. Edinburgh Journal of Botany. 50(3): 311-315

Galle, F. (1987) Azaleas Revised and Enlarged Edition. Timber Press, Inc.

Davidian, H. H. The Rhododendron Species Volume IV-Azaleas. Timber Press 1995

Don Hyatt's website: http://www.tjhsst.edu/~dhyatt/azaleas/

Sally Perkins, Salem, NH


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