Rhododendron calendulaceum

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Plant types and subtypes: Root Catalog, Trees & Shrubs, Shrubs, Deciduous

Light Requirements: part-sun, part-shade

Water Use: low, medium

Soil Moisture: dry, moist

Soil Description: acid, rich, average, loam, clay

Height: 10'-15'

Bloom Time: March, April, May, June

Bloom Color: orange

Leaf Color: green

Hardiness Zone: 6, 7, 8

Additional Tags: attracts bees, attracts birds, attracts butterflies, poisonous, shade garden plant

Rhododendron calendulaceum

Pricing & Availability


Rhododendron calendulaceum

Also known as:

flame azalea


butterfly azalea

Scientific Synonyms:

Azalea calendulacea, Azalea lutea


Rhododendron calendulaceum is likely the showiest of all the native azaleas. The common name "flame azalea", as well as the species epithet "calendulaceum" are presumably a reference to the flower buds and their resemblance to a candle flame. However, there are also many references to entire hill sides becoming ablaze with orange flowers when this azalea goes into bloom. The plants themselves are unusually tall, growing up to a height of 15' under ideal conditions. The tubular flowers are quite large as well, up to 3" in length and in diameter, and appear in terminal clusters of 5 to 15. The color is typically orange, but can tend towards more yellow or red hues, and is always intense.


The native range of this large deciduous azalea follows the Appalachian range from Alabama and Georgia up to Pennsylvania, with a few isolated populations even further north. It is adapted to hill-sides with heavy, acidic soil, exposed to filtered light. In cultivation, moist, well drained soil is best. It can tolerate strong exposure to direct sunlight (which will increase bloom production), but will require additional mulch to maintain adequate soil moisture. This might also lead to leaf scorch, particularly in hotter parts of its range. Bloom times will vary from late March in the south, to early June in the north, and will last for about 2 weeks. Zones 6-8


Rhododendron calendulaceum can be difficult to propagate by cuttings. If a vegetative method is preferred, you should try layering, but even this method can be slow in producing transplantable cuttings. It is easier to propagate from seed. Use a light, but moisture retentive medium, and maintain at a cool temperature, within 45 to 55 degrees. No pretreatment is required.

Native Range & Classification

Recorded County Distribution: USDA data

Native Range:

USDA Endangered Status:

  • Endangered: OH
  • Extirpated: PA


Kingdom Plantae Plants
Subkingdom Tracheobionta Vascular plants
Superdivision Spermatophyta Seed plants
Division Magnoliophyta Flowering plants
Class Magnoliopsida Dicotyledons
Subclass Dilleniidae
Order Ericales
Family Ericaceae Heath family
Genus Rhododendron rhododendron
Species Rhododendron calendulaceum flame azalea