Rhododendron calendulaceum, flame azalea
Carey, Jennifer H. 1994. Rhododendron calendulaceum, flame azalea. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/rhocae
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| RHOCAE | flame azalea | Rhododendron calendulaceum | Life Form: Plants/Shrub Kingdom: Plantae Class: Dicot Order: Ericales Family: Ericaceae Genus: Rhododendron | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Taxonomy
The currently accepted scientific name for flame azalea is Rhododendron calendulaceum (Michx.) Torr. (Ericaceae) [8,20]. There are no currently accepted infrataxa.
Synonyms
- Azalea calendulacea Michx. [8,20]
Other Common Names
No entry.
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].
States
- United States: AL, GA, KY, NC, OH, PA, SC, TN, VA, WV
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].
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].
Botanical Description
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 (Raunkiaer 1934)
- Phanerophyte
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].
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].
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].
Immediate Fire Effects
Rhododendrons are sensitive to fire [9]. Fire probably top-kills flame azalea.
Postfire Regeneration Strategy (Stickney 1989)
- Tall shrub, adventitious-bud root crown
Fire 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].
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.
Fire Regimes
For fire regime information, search FEIS for this species by entering the species name on the Advanced Search page and selecting “Fire Regime” as the publication type.
Fire Management Considerations
No entry.
Federal Status
None
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.
Importance to Wildlife and Livestock
No entry.
Palatability and Nutritional Value
No entry.
Cover Value
No entry.
Value for Rehabilitation or Restoration of Disturbed Sites
No entry.
Other Uses
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].
Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.
Forest and Range Ecosystems (Garrison et al. 1977)
- FRES13 Loblolly - shortleaf pine
- FRES15 Oak – hickory
- FRES18 Maple - beech - birch
BLM Physiographic Regions (Bernard and Brown 1977)
No entry.
Kuchler Plant Associations (Kuchler 1964)
- K104 Appalachian oak forest
- K109 Transition between K104 and K106
- K111 Oak - hickory - pine forest
SAF Cover Types (Eyre 1980)
- 44 Chestnut oak
- 52 White oak - black oak - northern red oak
- 53 White oak
- 55 Northern red oak
SRM Rangeland Cover Types (Shiflet 1994)
No entry.
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