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Publication #FPS503

 

Rhododendron austrinum Florida Flame Azalea1

Edward F. Gilman2

Introduction

Florida flame azalea is well-noted for its vivid display of yellow-orange, slightly fragrant, clustered blooms appearing in spring, before the new leaves emerge. Well-suited to mass plantings in natural woodland settings, Florida flame azalea makes a traffic-stopping showing whenever it is in full bloom. It is usually quite a surprise in flower since it generally goes unnoticed during the rest of the year.

General Information

Scientific name: Rhododendron austrinum
Pronunciation: roe-duh-DEN-drun oss-TRY-num
Common name(s): Florida flame azalea
Family: Ericaceae
Plant type: shrub
USDA hardiness zones: 6B through 9 (Fig. 1)
Planting month for zone 7: year round
Planting month for zone 8: year round
Planting month for zone 9: year round
Origin: native to Florida
Uses: mass planting; specimen; container or above-ground planter; trained as a standard; attracts hummingbirds
Availability: somewhat available, may have to go out of the region to find the plant

Description

Height: 6 to 10 feet
Spread: 4 to 8 feet
Plant habit: vase shape; upright
Plant density: moderate
Growth rate: slow
Texture: fine

Foliage

Leaf arrangement: alternate
Figure 1. 

Shaded area represents potential planting range.


[Click thumbnail to enlarge.]
Leaf type: simple
Leaf margin: entire
Leaf shape: ovate
Leaf venation: pinnate
Leaf type and persistence: deciduous
Leaf blade length: 2 to 4 inches
Leaf color: green
Fall color: yellow
Fall characteristic: not showy

Flower

Flower color: yellow-orange
Flower characteristic: pleasant fragrance; spring flowering

Fruit

Fruit shape: elongated
Fruit length: .5 to 1 inch
Fruit cover: dry or hard
Fruit color: brown
Fruit characteristic: inconspicuous and not showy

Trunk and Branches

Trunk/bark/branches: not particularly showy; typically multi-trunked or clumping stems
Current year stem/twig color: brown
Current year stem/twig thickness: thick

Culture

Light requirement: plant grows in part shade/part sun
Soil tolerances: clay; acidic; loam; sand;
Drought tolerance: moderate
Soil salt tolerances: poor
Plant spacing: 36 to 60 inches

Other

Roots: usually not a problem
Winter interest: no special winter interest
Outstanding plant: plant has outstanding ornamental features and could be planted more
Invasive potential: not known to be invasive
Pest resistance: long-term health usually not affected by pests

Use and Management

Florida flame azaleas are rather straggly and upright when very young but will spread out, the large, medium green leaves causing the branches to gently cascade down to the ground. A single specimen should be allowed at least six feet of spread to develop into the cascading form. These make a dramatic effect planted in mass three to five feet apart as part of a shrub border.

Rich, moist, acid soil in light shade with some direct sun, protected from harsh winds, is an ideal location for Florida flame azaleas. Azaleas grow best in filtered shade from tall trees, but will bloom poorly when in root competition with trees. Plants are very sensitive to drought. The soil must be open and porous, yet able to retain water well. A thick mulch is recommended to help ensure adequate moisture retention and root growth. Locate the plants so that they can receive frequent irrigation. Roots are located in the top several inches, even in sandy, well-drained soil.

Pruning is seldom necessary except to control shoots that extend above the normally mounded shape. Since plants bloom on the previous year's growth, any desired pruning should be done in spring after flowering. Pinching new shoots when they are several inches long increases branching and flower display.

The cultivar 'My Mary' has 2.5-inch-wide, single, fragrant yellow flowers.

Propagation is by seed sown in late fall on moist peat moss or by softwood cuttings taken in late spring.

Mites.

Pests and Diseases

Problems include iron deficiencies from too high a soil pH and mushroom root rot from over watering or poorly drained soil.

Footnotes

1.

This document is FPS503, one of a series of the Environmental Horticulture, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date September 1999. Revised June 2007. Reviewed June 2011. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Edward F. Gilman, professor, Environmental Horticulture Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, Dean.