Native Azaleas: Natural Color in the Shade Garden

Prepared by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University, 02/14.

HGIC 1094

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Among the most beautiful of South Carolina’s native flowering shrubs are the native azaleas. Gardeners in all parts of the state can enjoy the spectacular flowers and delightful fragrance of many of these eastern native shrubs.

There are numerous native azalea species in South Carolina, with bloom times from early spring through late summer. The flower colors range from white to many shades of pink, red, yellow, orange and salmon. These deciduous shrubs (that is, they lose their leaves during the winter) are members of the genus Rhododendron, which also includes the evergreen azaleas and rhododendrons. Mature plant sizes vary from two-foot tall spreading species to 15 foot tall tree-like shrubs.

Popular choices include the Florida flame azalea (Rhododendron austrinum), which blooms in April with orange, yellow or scarlet flowers. This magnificent species is certainly one of the showiest of the native azaleas.  

Florida flame azalea (Rhododendron austrimum)
Florida flame azalea (Rhododendron austrinum)
Joey Williamson, ©2013 HGIC, Clemson Extension

The piedmont azalea (R. canescens) is one of the earliest bloomers and begins its show with pale pink flowers in early April. ‘Camilla’s Blush’ is a selection with ball-shaped trusses of soft pink blossoms, and grows to eight feet.

Piedmont azalea (Rhododendron canescens).
Piedmont azalea (Rhododendron canescens).
Joey Williamson, ©2013 HGIC, Clemson Extension

The sweet azalea (R. arborescens) has white blooms, dark green foliage and is very fragrant. This June bloomer usually needs relatively moist soil. This species will grow to six to eight feet.

The flame azalea (R. calendulaceum) flowers in May and typically has large orange blooms, but again, colors vary widely. ‘Kelsey’s Flame’ is an outstanding cultivar with striking yellow and orange flowers, and grows to eight to ten feet.

Other native azaleas available include the coastal azalea (R. atlanticum), the pinxterbloom azalea (R. periclymenoides), the swamp azalea (R. viscosum) and numerous cultivars of crosses between the native azaleas. These crosses have added to the many color variations and color combinations naturally present in our native azaleas.

Flame azalea (Rhododendron calendulaceum).
Flame azalea (Rhododendron calendulaceum).
Joey Williamson, ©2013 HGIC, Clemson Extension

From a landscaping perspective, these native species can be grouped by flower color: white, pink or orange. However, considerable variation in flower color occurs within each species, and nurserymen have selected those with the most stunning colors. Recently, more garden centers in South Carolina offer native azaleas for sale, including many cultivars and hybrids of these species that have been selected for superior flower color. For more information on the native azalea species, see Table 1 below. Table 2 below lists examples of selections and hybrids of the Southeastern native azaleas often available for sale. For photos of the many species and cultivars, please see HGIC 1058, Azaleas.

Landscape Site

Native azaleas prefer cool, partially shaded sites with rich, moist woodland soil. But exceptions occur as some will tolerate dry woodland soil, and others flourish in what would be considered excessively moist areas. They can be planted any time of the year, but greater success may be obtained with an autumn planting. However, spring is usually the time these shrubs are found at the garden centers.

When choosing a site for a native azalea, morning sun and afternoon shade will be best. In general, species that flower in June or later may require more shade, as the delicate flowers will not tolerate the hot summer sun. For overall plant health, adequate soil moisture can help compensate for the excessive summer heat.

Soil Preparation & Planting

Native azaleas prefer acid soils with a pH 5.2 to 5.8, and most South Carolina soils are naturally acidic. Unless directed by a soil test to add lime to the soil, you should not lime the soil near these plants, because their foliage may become yellow or chlorotic.

At planting, it’s always best to loosen and prepare the soil in large planting beds, rather than individual holes. One of the best forms of organic matter to incorporate with the existing soil is composted pine bark, which is naturally acidic. These shrubs must be planted at the same level in the soil as they were in the container, or slightly higher if the soil is poorly drained.

Be sure to mulch the plants with a three-inch thick layer of pine bark, pine needles or leaves to help keep the soil cool and to conserve soil moisture. However, the mulch should not be piled against the stem or trunk of the plants. Then be sure to water the plants well initially to settle the soil. Remember that until a plant is established, it is dependent upon the homeowner for water. They will need to be watered weekly during the first growing season if there is insufficient rainfall.

Fertilization

Fertilize native azaleas lightly in the spring and early summer with a well-balanced, extended-release, azalea fertilizer. Fertilizer examples are Lilly Miller Ultra Green Azalea, Camellia & Rhododendron Food (10-5-4), Vigoro Azalea, Camellia & Rhododendron Food (10-8-8), and Scotts Evergreen, Flowering Tree & Shrub Fertilizer (11-7-7).

Complete, acid-forming organic fertilizers are also excellent choices for use on native azaleas, such as Espoma Holly-Tone (3-4-3) or Fertrell Holly Care (4-6-4). Never fertilize azaleas in the late fall as this may delay dormancy and result in plant injury.

With proper site selection and planting, you will be pleasantly surprised at how well they perform and pleased with their exceptional beauty. For additional information on planting procedures for shrubs, please see HGIC 1052, Planting Shrubs Correctly.


Table 1. Native Deciduous Azaleas of the Southeastern US.
Native Azalea Rhododendron SpeciesFlower ColorBloom TimePlant SizeComments
*Native populations exist within South Carolina
R. alabamense
Alabama Azalea
Snowy white flowers with a prominent yellow blotch Mid-April-May Low to medium, 2 - 6’ Spreads by stolons. Native to GA, AL, TN & FL panhandle. Distinct lemon-spice fragrance. Propagates easily from cuttings.
R. arborescens*
Sweet Azalea
White to blush pink flowers with red stamens Early May - June To 15’ Native from AL to PA primarily along Appalachians, especially near streams. Very strong fragrance. Easy to propagate.
R. atlanticum*
Coastal Azalea
White flowers are often blushed with pink – some with a yellow blotch Early April - May Low, 1 - 5’ Native from GA through NJ along the coast. Spreads by stolons. Easy to propagate. Fragrant.
R. austrinum
Florida Flame Azalea
Shades of orange through gold and yellow. No blotch. The tube of the flower is often flushed with red. Very long stamens Late March - April To 15’ Native to lower AL, GA & FL panhandle. Fragrant. Heat tolerant. Easy to propagate
R. calendulaceum*
Flame Azalea
Wide range of colors from clear yellow, through shades of orange, to brilliant red Early May - June To 12 - 15’ Native in Appalachians & piedmont from GA to WV. Large flowers. Difficult to propagate from cuttings.
R. canescens*
Piedmont Azalea
Shades of pink to white with no blotch. Long stamens Late March - April 10 - 15’ Native over lower Southern states. Fragrant. Easy to propagate.
R. eastmanii*
Eastman’s Azalea
White flowers with yellow blotch & red stamens May Native in SC only; less common.
R. flammeum*
Oconee Azalea
Shades of yellowish orange, through orange to deep red. Flowers usually have a blotch. Early-April - early May Variable Native in SC & GA. Heat tolerant. Not fragrant.
R. periclymenoides*
Pinxterbloom Azalea
White to pale or deep pink flowers. Long stamens. Mid-April- mid-May 3 - 8’ Native from AL through New England. Slightly fragrant. Moderate to easy to propagate.
R. prunifolium
Plum Leaf Azalea
Orange to vivid red flowers Late June - July, or later To 15’ Native to AL & GA. Easy to propagate by cuttings & from seeds. Not fragrant.
R. vaseyi
Pinkshell Azalea
Delicate pink to white flowers April To 15’ Native to mountains of NC. Less common.
R. viscosum*
Swamp Azalea
Flowers white, sometimes pinkish tinge. Mid-May - June 3 - 15’ Spicy fragrance. Tolerates damp or wet soil. Spreads by stolons. Easy to propagate.

Table 2. Examples of Selections and Hybrids of Native Deciduous Azaleas.
Cultivars of Hybrid Native AzaleasFlower ColorBloom TimePlant Size
‘Camilla’s Blush’ Soft pink flowers; fragrant. Early April 8’
‘Darlin’s Dream’ White flowers with lavender-pink edging and golden yellow throat. Mid-April 10 - 12’
‘Firecracker’ Intense orange flowers with a touch of red; very fragrant. April 8’
‘Kelsey’s Glow’ Bright yellow flowers with reddish hues. Mid-April 10 - 12’
‘Kennell’s Gold’ Golden yellow flowers; fragrant. Early April 12 - 15’
‘Lisa’s Gold’ Bright gold flowers. Early April 10 - 12’
‘Lucky Lady’ Vibrant red flowers with peachy centers. Mid-April 6 - 8’
‘My Mary’ Pure yellow flowers; fragrant. April 8’
‘Nacoochee Princess’ Large, slender white flowers with tinge of pink; fragrant April 8 - 10’
‘Rosy Pink Nudiflorum’ Pink flowers – rose in bud. Early April 6 - 8’
‘Rushin’s Austrinum’ Bright yellow flowers with clear yellow tubes; very fragrant. Mid-April 8 - 10’
‘Sautee Sunset’ Peachy-pink flowers with soft yellow throat. Mid-April 6 - 8’
‘Summer Eyelet’ White flowers; spicy fragrance. July 6’
‘Tangerine Delight’ Bright orange flowers. Late April 10’

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