Index of Species Information

SPECIES:  Rhododendron calendulaceum


SPECIES: Rhododendron calendulaceum
AUTHORSHIP AND CITATION : Carey, Jennifer H. 1994. Rhododendron calendulaceum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: [].

ABBREVIATION : RHOCAE SYNONYMS : Azalea calendulacea Michx. [8,20] SCS PLANT CODE : RHCA4 COMMON NAMES : flame azalea TAXONOMY : The currently accepted scientific name for flame azalea is Rhododendron calendulaceum (Michx.) Torr. (Ericaceae) [8,20]. There are no currently accepted infrataxa. LIFE FORM : Shrub FEDERAL LEGAL STATUS : See OTHER STATUS OTHER STATUS : The status of flame azalea in New York and Maryland is undetermined. Although historically reported in these states, no extant populations are known [3,30]. Flame azalea is listed as endangered in Ohio [13]. It is secure throughout the rest of its range.


SPECIES: Rhododendron calendulaceum
GENERAL DISTRIBUTION : Flame azalea occurs in the Appalachian Mountains from southern Pennsylvania and southeastern Ohio south to northern Georgia and northern Alabama [8,20,28].  Historically it has been reported as far north as southeastern New York [30]. ECOSYSTEMS :    FRES13  Loblolly - shortleaf pine    FRES15  Oak - hickory    FRES18  Maple - beech - birch STATES :      AL  GA  KY  NC  OH  PA  SC  TN  VA  WV BLM PHYSIOGRAPHIC REGIONS : NO-ENTRY KUCHLER PLANT ASSOCIATIONS :    K104  Appalachian oak forest    K109  Transition between K104 and K106    K111  Oak - hickory - pine forest SAF COVER TYPES :     44  Chestnut oak     52  White oak - black oak - northern red oak     53  White oak     55  Northern red oak SRM (RANGELAND) COVER TYPES : NO-ENTRY HABITAT TYPES AND PLANT COMMUNITIES : Flame azalea occurs in mixed deciduous forests [11,19,26].  It occurs in the well developed shrub layer of oak (Quercus spp.) forests of southern and western exposures, and with more mesic site species in ravines. Flame azalea is an important understory shrub in forests formerly codominated by American chestnut (Castanea dentata) [1,26]. Flame azalea occurs with other ericaceous shrubs including rosebay rhododendron (Rhododendron maximum), mountain-laurel (Kalmia latifolia), highbush cranberry (Vaccinium corymbosum), and huckleberry (Gaylussacia spp.) [1].  It occurs at low coverage in the grassy bald vegetation type and the grassy bald edge ecotone [26].


SPECIES: Rhododendron calendulaceum
IMPORTANCE TO LIVESTOCK AND WILDLIFE : NO-ENTRY PALATABILITY : NO-ENTRY NUTRITIONAL VALUE : NO-ENTRY COVER VALUE : NO-ENTRY VALUE FOR REHABILITATION OF DISTURBED SITES : NO-ENTRY OTHER USES AND VALUES : Flame azalea is considered one of the finest ornamental shrubs in the United States [14]. OTHER MANAGEMENT CONSIDERATIONS : Many nursery cultivars have been developed from flame azalea.  It is highly sought after for its striking colors and relative cold hardiness [17,18].  In states where flame azalea is rare, illegal collection is a threat [13].


SPECIES: Rhododendron calendulaceum
GENERAL BOTANICAL CHARACTERISTICS : Flame azalea is a native, deciduous, erect, much-branched shrub that grows to 10 feet (3 m) in height.  Its morphology and phenology are highly variable [28].  The fruit is a capsule [8,20,29].  Rhododendrons (Rhododendron spp.) have a diffuse shallow root system [22].  Flame azalea is not rhizomatous [8]. RAUNKIAER LIFE FORM :       Phanerophyte REGENERATION PROCESSES : Rhododendron fruits split along the sides soon after ripening and release many small seeds which are disseminated short distances by wind.  Moist mineral soil or a short moss seedbed is required for seedling establishment [9,16]. Rhododendrons sprout from the root crown when top-killed [9]. Propagation techniques from cuttings are described [5,23].  Day-night temperatures and durations for maximizing flame azalea seedling growth are reported [12]. SITE CHARACTERISTICS : Flame azalea occurs on south- and west-facing slopes of mountainous sites.  It occurs on submesic to subxeric sites at lower elevations and on submesic sites at elevations above 5,000 feet (1,500 m) [26]. Adequate humidity and soil moisture are required.  Rhododendrons grow best on acidic soils from pH 4.5 to 5.5 [4]. SUCCESSIONAL STATUS : Facultative Seral Species Flame azalea is intermediate in shade tolerance.  It grows well in the indirect light of open woods but declines as forests mature and canopies close [13]. SEASONAL DEVELOPMENT : Flame azalea flowers in late April and May at lower elevations and in June and early July at higher elevations [28].  Flowers appear before or with the leaves and last several weeks.  Fruit matures July through September [2,8,20,29].


SPECIES: Rhododendron calendulaceum
FIRE ECOLOGY OR ADAPTATIONS : Flame azalea is probably fire resistant because of its ability to sprout from the root crown.  Fire may open up maturing forest canopies and rejuvenate declining flame azalea.  Flame azalea occurs in oak woods that periodically experience fire [27]. POSTFIRE REGENERATION STRATEGY :    Tall shrub, adventitious-bud root crown


SPECIES: Rhododendron calendulaceum
IMMEDIATE FIRE EFFECT ON PLANT : Rhododendrons are sensitive to fire [9].  Fire probably top-kills flame azalea. PLANT RESPONSE TO FIRE : Flame azalea probably sprouts from the root crown when top-killed.
The Research Project Summary Early postfire effects of a prescribed
fire in the southern Appalachians of North Carolina
provides information
on prescribed fire and postfire response of plant community species,
including flame azalea, that was not available when this species review
was originally written.


SPECIES: Rhododendron calendulaceum
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Seeds of woody plants in the United States.        Agric. Handb. 450. Washington, DC: U.S. Department of Agriculture,        Forest Service: 709-712.  [7739] 17.  Pellett, N.; Halvorsen, L. 1981. The search for hardy azaleas        Rhododendron calendulaceum, Mt. Pisgah in North Carolina. American        Nurseryman. 153(11): 7, 107.  [23051] 18.  Pellett, N. E.; Rowan, N.; Aleong, J. 1991. Cold hardiness of various        provenances of flame, roseshell, and swamp azaleas. Journal of the        American Society of Horticultural Science. 116(1): 23-26.  [23052] 19.  Quarterman, Elsie; Turner, Barbara Holman; Hemmerly, Thomas E. 1972.        Analysis of virgin mixed mesophytic forests in Savage Gulf, Tennessee.        Bulletin of the Torrey Botanical Club. 99(5): 228-232.  [11128] 20.  Radford, Albert E.; Ahles, Harry E.; Bell, C. Ritchie. 1968. Manual of        the vascular flora of the Carolinas. Chapel Hill, NC: The University of        North Carolina Press. 1183 p.  [7606] 21.  Raunkiaer, C. 1934. The life forms of plants and statistical plant        geography. Oxford: Clarendon Press. 632 p.  [2843] 22.  Read, D. J. 1983. The biology of mycorrhiza in the Ericales. Canadian        Journal of Botany. 61: 985-1004.  [10602] 23.  Sanders, C. R. 1978. Some aspects of the propagation of Rhododendron,        Mahonia, and Ilex by cuttings. Combined Proceedings, International Plant        Propagators Society. 28: 228-232.  [10693] 24.  Stickney, Peter F. 1989. Seral origin of species originating in northern        Rocky Mountain forests. Unpublished draft on file at: U.S. Department of        Agriculture, Forest Service, Intermountain Research Station, Fire        Sciences Laboratory, Missoula, MT; RWU 4403 files. 7 p.  [20090] 25.  U.S. Department of Agriculture, Soil Conservation Service. 1982.        National list of scientific plant names. Vol. 1. 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