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Rhododendron calendulaceum (Flame azalea)
Cressler, Alan

Rhododendron calendulaceum

Rhododendron calendulaceum (Michx.) Torr.

Flame Azalea

Ericaceae (Heath Family)

Synonym(s): Azalea calendulacea, Azalea lutea

USDA Symbol: RHCA4

USDA Native Status: L48 (N)

Flame azalea is usually an upright-branched deciduous shrub, 6-12 ft. tall and equally as wide, with large, showy, funnel-shaped flowers in clusters of 5 or more. Summer foliage is medium green and the fall color is subdued yellow to red. The non-fragrant flowers, appearing before or with the leaves, vary in color from pale yellow to apricot to brilliant scarlet red. A deciduous shrub with terminal clusters of tubular, vase-shaped, orange, red, or yellow flowers.

This beautiful southern Azalea forms striking displays on some of the grassy balds of the southern Appalachians. A wide variation of color forms occurs, from all shades of yellow to orange-yellow and scarlet. The flowers appear before or with the new leaves. This species is extensively planted as an ornamental. Like most members of the heath family, it does best in acid soil.


From the Image Gallery

34 photo(s) available in the Image Gallery

Plant Characteristics

Duration: Perennial
Habit: Shrub
Leaf Retention: Deciduous
Leaf Arrangement: Alternate
Leaf Complexity: Simple
Breeding System: Flowers Bisexual
Fruit Type: Capsule
Size Notes: Usually shrub-like, up to about 12 feet tall. Sometimes tree-like, up to about 30 feet tall.
Autumn Foliage: yes
Fruit: Brown

Bloom Information

Bloom Color: Red , Orange , Yellow
Bloom Time: Mar , Apr , May , Jun , Jul , Aug


USA: AL , CT , GA , KY , MD , NC , NY , OH , PA , SC , TN , VA , WV
Native Distribution: NY to s. OH, s. to GA & MS
Native Habitat: Dry, rocky, mountain woods; heath balds

Growing Conditions

Light Requirement: Part Shade
Soil Moisture: Moist
Soil pH: Acidic (pH<6.8)
Soil Description: Well-drained soil.
Conditions Comments: Rhododendron calendulaceum tolerates dry soil. It needs at least a few hours of sun each day, proper soil, and careful pruning when young for the best floral displays. Floral show lasts nearly two weeks. Good cultural practices reduce the incidence of disease and insect damage.


Warning: Rhododendrons contain poisonous substances and should not be ingested by humans or animals. Honey made from flowers also may be toxic. POISONOUS PARTS: All parts. Highly Toxic, May be Fatal if eaten. Symptoms include salivation, watering of eyes and nose, abdominal pain, loss of energy, depression, nausea and vomiting, diarrhea, weakness, difficult breathing, progressive paralysis of arms and legs, coma. Toxic Principle: Andromedotoxin. (Poisonous Plants of N.C.)
Attracts: Birds

Value to Beneficial Insects

Special Value to Bumble Bees

This information was provided by the Pollinator Program at The Xerces Society for Invertebrate Conservation.


Description: Combine seeds loosely with sphagnum moss and sprinkle lightly over a 2:1 perlite/peat mixture. Germinate under mist or a plastic tent. Optimum temperatures for germination are 45-50 degrees. Transplant seedlings to acid soil with a high content of orga
Seed Treatment: No pretreatment is necessary.
Commercially Avail: yes

From the National Organizations Directory

According to the species list provided by Affiliate Organizations, this plant is on display at the following locations:

Delaware Nature Society - Hockessin, DE
Mt. Cuba Center - Hockessin, DE


Bibref 1620 - Gardening with Native Plants of the South (Reprint Edition) (2009) Wasowski, S. with A. Wasowski

Search More Titles in Bibliography

Web Reference

Webref 38 - Flora of North America (2019) Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.

Additional resources

USDA: Find Rhododendron calendulaceum in USDA Plants
FNA: Find Rhododendron calendulaceum in the Flora of North America (if available)
Google: Search Google for Rhododendron calendulaceum


Record Modified: 2022-10-20
Research By: TWC Staff

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