- Deciduous Azaleas Glendoick Gardens
- Deciduous azalea Hybrids £14 each ex VAT
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- common yellow azalea – Rhododendron luteum
- ‘Admiral Semmes’
- ‘Camilla’s Blush’
- ‘High Tide’
- ‘Linda Guy’
- ‘Lisa’s Gold’
- ‘My Mary’
- ‘Summer Eyelet’
- ‘Tallulah Sunrise’
- ‘Tangerine Delight’
- Native Azaleas: Natural Color in the Shade Garden
- Landscape Site
- Soil Preparation & Planting
- AzaleaEssential Southern Plant
Deciduous Azaleas Glendoick Gardens
Size 1.2m+ after 10-20 years.
Hardiness very tough: mostly H5-6.
The Mollis and Exbury hybrids are well-known, but the species are becoming more and more popular with their subtle, often scented flowers.
Many deciduous azaleas are late flowering so extend the season.
Most deciduous azaleas are very tough (H5-6) and wind/exposure tolerant.
They can be cut back to keep them in bounds.
Autumn colour in most varieties: red, orange, yellow shades as the leaves fall.
Plant them in full sun or part day shade. In southern England they will flower in more shade.
Azaleas, Ken Cox, Glendoick from Glendoick on Vimeo.
Deciduous Azalea Species
£14 each ex VAT Varieties marked * are scented
AZALEA ALBRECHTII H4-5 Deep rose, early. One of the finest azalea species. Early growth, best with some shelter.
AZALEA ARBORESCENS * H5-6 Sweet heliotrope-scented white tubular fls with contrasting purplish red style, late. One of the best white scented species.
AZALEA CALENDULACEUM H6 Small vibrant orange fls. The famous ‘flame azalea’ of eastern U.S.A. A parent of many of the best hybrids.
AZALEA CANADENSE H6 Small frost resistant purple flowers in early May. The neatest and most compact deciduous azalea species. White and purple forms.
AZALEA LUTEUM (Azalea pontica) * H4-5 Sweetly-scented yellow. Excellent autumn colour. Easily grown and good for naturalising. The most popular azalea species. ‘GOLDEN COMET’ Selection from Rhododendron Species Foundation, USA
AZALEA MOLLE ssp. JAPONICUM (syn. A. Mollis)H5 1-2m. Orange or salmon-pink flowers in May. Very hardy, easy and compact.
AZALEA OCCIDENTALE H4 * Large-flowered scented white, flushed pink, orange-yellow flare. Late. ‘CRESCENT CITY DOUBLE’ form with double flowers.
AZALEA QUINQUEFOLIUM H4 Low-Med EM Small white fls. Beautiful foliage. Choice. Very hard to propagate: usually a waiting list for this.
AZALEA SCHLIPPENBACHII H4-5 Beautiful pale pink, early. Autumn colour. Compact. Early growth needs protection. Often considered the finest azalea species.
AZALEA VASEYI H5-6 Lovely pink flowers in April-May. Splendid, usually scarlet autumn colour. Charming in every way. ‘WHITE FIND’ white
AZALEA VISCOSUM* H5 (swamp honeysuckle) Sweetly-scented small white flowers in June-July with a fine scent.
Deciduous azalea Hybrids £14 each ex VAT
Grow to 1.2-1.6m, ultimately 2-2.5m+. Can be pruned. Hardiness H5-6.
There are several well known categories of deciduous azalea hybrids.
GHENT/RUSTICA FLORE PLENO (GH) H6 hybrids mostly raised in the 19th century and have small, often double flowers. May-June.
MOLLIS (MO) H6. Showy flowers in May. Slower growing than the other groups. Not scented.
EXBURY or KNAPHILL (EX) H6 the largest flowered and brightest group of azalea hybrids. Flowering in late May and early June. Some are scented and some have good autumn colour.
OCCIDENTALE (OC) H4 white to pale pink or pale yellow range, strongly or lightly scented. Most are June flowering.
VISCOSUM (VIS) pink to white scented flowers. H4-5
Scented are marked *
AZALEA ARNESON’S GEM (MO) Spectacular large orange-yellow fls, Outstanding. Vigorous.
AZALEA BEN SERIES (EX) NEW Scottish Mountain Series. A new range of Glendoick double azalea hybrids in a range of colours: BEN CRUACHAN cream, pink edge, BEN LAWERS deep pink, BEN LOMOND pale pink, BEN VRACKIE salmon pink, orange centre.
AZALEA CROSSWATER RED (EX) One of the reddest azaleas. Upright habit. Late.
AZALEA DELICATISSIMA (OC) * Cream, tinged pink, yellow flare, scented.
AZALEA EXQUISITA (OC) * Pale pink-apricot with orange centre, scented.
AZALEA FIREBALL (EX) $ Deep orange-red. Reddish leaves.Tall. Very free-flowering.
AZALEA GIBRALTAR (EX) Vivid orange. The most popular azalea, very free-flowering from a young age and fairly compact/slow-growing.
AZALEA GOLD TOPAZ (EX) Pure yellow.
AZALEA IRENE KOSTER (OC) * Light pink scented flowers in May-June.
AZALEA JOCK BRYDON (OC) * Pink with a bold reddish blotch, scented. Vigorous and really striking.
AZALEA JUNE FIRE (EX) Fine red, very late. Compact and spreading, fine colour.
AZALEA JUNIDUFT NEW (VIS)* Low-Med L Late flowering fragrant medium pink.
AZALEA KLONDYKE (EX) Large orange-yellow flowers. Reddish bronze foliage. Compact.
AZALEA LEMON DROP (VIS) * Scented small creamy yellow in mid July. Glaucous foliage.
AZALEA MIDSUMMER MERMAID. (VIS) Late pink, scented. Blue leaves.
AZALEA OCCIDENTALE X ARBORESCENS (OC) * Scented pale pink, late.
AZALEA PARKFEUER (EX) rich orange-red.
AZALEA PERSIL (EX) Fine large-flowered white with a yellow flare. The most popular white hybrid.
AZALEA ROSATA (VIS) * Lovely lightly scented deep pink. Bushy, and tough.
AZALEA SOIR de PARIS (VIS) * Pale pink with orange throat, lightly scented. Good habit and grey-green foliage.
AZALEA STRAWBERRY ICE (EX) The most popular pink. Bronzy young foliage.
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The Arboretum in Hørsholm > Plant Descriptions – Plant of the Month > common yellow azalea
common yellow azalea – Rhododendron luteum
common yellow azalea
Ericaceae (heath family)
up to 3 M in our collection
Late May & June
Eastern Europe and Caucasus north to Poland
The 45 year old Rhododendron luteum in the picture is from seed received from Arboretum Mlynany Bratislava, Slovak Republic. The plant pictured here can be found in the azalea collection adjacent to our Rhododendron Dalen: in square 2104, position 2938.
This months plant Rhododendron luteum is a dominate element in the arboretum in early June with its strong scent and brilliant yellow flowers. The scent can be detected dozens of meters from massive plantings, both of which create a lasting impression.
Rhododendron luteum belongs to section Pentathera within the genus Rhododendron. In this section leaves are alternate, stamens are 5 and the flower petals are densely hairy on the outer surfaces. All but two species within this section come from North America. One of the two exceptions comes from Eastern China and Japan, and the other (R. luteum) from Europe. This is Europes only azalea.
The flowering season of Rhododendron luteum is rather long for a rhododendron, because the flowers in each inflorescence open in succession. An attractive autumn leaf colour is also typically for the species. We have about 75 examples of
Rhododendron luteum in our collection in Hørsholm. But because of the massive dense plantings in a few areas it is difficult to count them all. Our oldest living plants came from the J. Madsen Nursery, in the town of Middelfart, Denmark, in 1952. Our documented, wild-collected specimens come from several places in the Caucasus, as well as from Greece and Turkey.
Rhododendron luteum was originally named Azalea pontica by Carl von Linne, was renamed Rhododendron flavum, and finally the given the name R. luteum in 1830. Sometimes the old names are stilled used. It has been grown in Denmark at least as early as 1831. It is grown in much of Europe as a garden plant and has naturalized in Britain but is not reported to be a problem there in contrast to R. ponticum. In its native range it can be a difficult weed that spreads with underground runners invading and reducing the productivity of pastures.
These are vigorous deciduous upright shrubs that can spread by underground runners. The oblong leaves are 5 to 15 cm long and 1.5 to 4 cm wide. The upper and lower surfaces are pubescent at first, but later they are hairless except for a few sticky hairs. They often have fine autumn leaf colours in red, and orange. Young twigs and flower stalks can also have sticky hairs. The flowers open before or at the same time as the leaves and open in succession within a given inflorescence. This later trait is variable in our collection, with some plants opening their flowers more or less simultaneously and other over a longer time. The petals form a funnel-shaped flower with sticky hairs on the outside. They are bright yellow with a darker blotch and strongly fragrant. Occasionally orange coloured flowers are reported. It is distinguished from its close relative R. austrinum by having a shorter flower-tube and by the strong scent and the fact that it grows in eastern Europe and western Asia.
This is an excellent garden plant for Denmark. Flowering is reduced in strong shade and the plants under densest shade in our collection produce no flowers at all. Pictures from its native range indicate it often grows on open slopes. Because it spreads by runners, it is possible to regenerate exact copies of especially desirable mother plants. However, it also produces abundant viable seed and is more often regenerated by seed. Because of the ease of regeneration it is often used as understock for grafting. Soon after its introduction it was used to produce numerous early hybrids.
Bean, W.J. 1976 Trees and Shrubs Hardy in the British Isles Vol III. N-Rh. Bean and Murray publishers. 973 pp.
Cox, P.A. 1990. The Larger Rhododendron Species. B.T. Bratsford Ltd. London 389 pp.
Cox, P.A. & Cox, K.N.E. 1997. The Encyclopedia of Rhododendron species. Glendoick Publishing, Perth Scotland. 396 pp.
Davidian, H.H. 1995. The Rhododendron Species. Vol IV. Azaleas. Timber Press Inc. Portland. 184 pp.
3Jørgensen, Per M. 2003. Rhododendron i det norske arboret på Milde. 2nd addition, Vigmostad & Bjørke AS, Bergen. 264 pp.
Native azaleas are deciduous and they do not care for dry areas and require good drainage. They won’t thrive in poorly drained, clay soil where they may develop root rot or in sun where they may burn. These plants perform best in dappled shade along woodland edges, shade gardens or above creek and pond banks.
Fragrant. Rhododendron ‘Admiral Semmes’ Native Azalea. Yellow 10′ – 15′. Well suited for our heat and humidity, is considered to be a trouble free native azalea. Large, showy flowers appear in late spring which will steal the show in your landscape. Blooms are a vibrant yellow and highly fragrant. ‘Admiral Semmes’ is a fast growing, large shrub so be sure to give it space! A stunning specimen for a wooded area, ‘Admiral Semmes’ will show up for a distance while in bloom.
Fragrant. Rhododendron ‘Camilla’s Blush’ Native Azalea Soft pink 6′ – 8′. This deciduous native is frequently seen as a selection of Piedmont azaleas. ‘Camilla’s Blush’ has highly fragrant, showy, pale pink flowers in spring. It is a must have for the scented garden. Like most native azaleas, ‘Camilla’s Blush’ does not like wet feet so plant this beauty in a well drained spot where it will get some relief from our hot Georgia sun!
Rhododendron ‘Gibraltar’ Exbury hybrid azalea. Orange, 6′. ‘Gibraltar’ is an exceptional flowering shrub with huge trusses of flowers featuring fringed, bright orange red petals. The fringed petal edges have a crepe paper like look. ‘Gibraltar’ blooms mid-season and has very heavy buds. This deciduous azalea is fragrant, hardy, and easy to grow.
Rhododendron ‘High Tide’ Deciduous, 5′-8′. Ivory with with gold center and light pink flush to the petals. Fragrant.
Rhododendron ‘Linda Guy’ 6-8′. Gorgeous flowers in a bright pink color. ‘Linda Guy’ will fill your garden with a wonderful spicy aroma. This native Azalea is an Aromi hybrid produces abundant clusters of red buds which open to large, true pink petals with a spicy sweet scent. Blooms have a golden yellow blotch.
Fragrant. Rhododendron ‘Lisa’s Gold’ Native Azalea. Gold yellow 10′ – 12′. Very fragrant, golden yellow blooms in late spring. An early bloomer for a native, ‘Lisa’s Gold’ puts on quite a show and will fill the air with its wonderful scent. A mid size to tall bush, give her plenty of space to grow. Habit is open and airy, ‘Lisa’s Gold’ may be planted with other denser bushes in a mixed border or as a specimen.
Fragrant. Rhododendron ‘My Mary’ Native Azalea. Orange yellow 4′ – 6′. A deciduous native hybrid rhododendron with showy, very fragrant flowers in late spring. The blooms are a stunning orange yellow, tubular shaped and are very attractive to butterflies and hummingbirds. While in bloom, ‘My Mary’ will scent your entire yard. Foliage is a medium to pale green and emerge late in the season. ‘My Mary’ is a beautiful shrub for a woodland garden, mass plantings or shrub border.
Fragrant. Rhododendron ‘Summer Eyelet’ Native Azalea. Pure white 5′. This native features an open, airy shape. ‘Summer Eyelet’ blooms late in the season and will fill a yard with a wonderful, spicy clove like scent. Flowers are pure white with lovely red stamens. A strong growing selection of the native viscosum azalea, ‘Summer Eyelet’ is a desirable shrub for a shady spot in the garden.
Fragrant. Rhododendron x ‘Tallulah Sunrise’ Native Azalea bright orange.
Fragrant. Rhododendron ‘Tangerine Delight’ Native Azalea. Orange 10′. A hybrid of native species, deciduous. Blooms mid spring with bright orange, show stopping flowers. ‘Tangerine Delight’ is among the easiest of the native varieties to grow and a great choice for starting a native collection. ‘Tangerine Delight’ is a prolific bloomer and considered among the best of the orange blooming varieties.
Deciduous and Native Azaleas varieties for sale in our plant nursery garden center are subject to change.
Native Azaleas: Natural Color in the Shade Garden
Florida flame azalea (Rhododendron austrinum).
Joey Williamson, ©2013 HGIC, Clemson Extension
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.
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).
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.
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.
Flame azalea (Rhododendron calendulaceum).
Joey Williamson, ©2013 HGIC, Clemson Extension
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.
Fertilize native azaleas lightly in the spring and early summer with a well-balanced, extended-release, acid-forming, azalea fertilizer. By well-balanced, this means to look for nutrients in the ratio of 2-1-1. Never fertilize azaleas in the late fall with these high nitrogen fertilizers, as this may delay dormancy and result in plant injury.
Fertilizer examples are:
Complete, acid-forming organic fertilizers are also excellent choices for use on azaleas, and these are great to mix into the soil at planting, as well as for use with spring fertilization. They are typically not as nutrient rich, and because of both the low nitrogen content and inability to burn the roots, they can be used to mix lightly into the soil in the fall at planting. Organic acid-forming fertilizer examples are:
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 Species||Flower Color||Bloom Time||Plant Size|
| R. alabamense
|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*
|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*
|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*
|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*
|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*
|White flowers with yellow blotch & red stamens||May||Native in SC only; less common.|
| R. flammeum*
|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*
|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
|Delicate pink to white flowers||April||To 15’||Native to mountains of NC. Less common.|
| R. viscosum*
|Flowers white, sometimes pinkish tinge.||Mid-May- June||3 – 15’||Spicy fragrance. Tolerates damp or wet soil. Spreads by stolons. Easy to propagate.|
|*Native populations exist within South Carolina|
Table 2. Examples of Selections and Hybrids of Native Deciduous Azaleas.
|Cultivars of Hybrid Native Azaleas||Flower Color||Bloom Time||Plant 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’|
AzaleaEssential Southern Plant
- Evergreen and deciduous shrubs
- For zones, see below
- Filtered sunlight
- Regular to ample water
- Leaves are poisonous if ingested
Rhododendrons and azaleas are arguably the South’s favorite shrubs. Many people think of them as entirely different plants, but they both belong to the genus Rhododendron, which comprises more than 800 species and 10,000 named selections. Even to the untrained eye, one difference between the two groups is obvious: rhododendrons generally have much larger leaves. From a technical standpoint, rhododendron flowers are bell shaped and have ten or more stamens, while azalea blooms are typically funnel shaped and have five stamens.
By making their choices carefully, gardeners in almost every part of the South can enjoy some of these plants, even if that means growing them in containers. Rhododendrons generally do better in the Upper and Middle South, though a number of selections thrive in the Lower South. Azaleas, however, are more accommodating; with the necessary attention to soil, light, and proper selection, they can be grown throughout the South.
Rhododendrons and azaleas have much the same basic requirements for soil and water. They need acid, well-drained, organically enriched soil that should neither get too dry nor remain soggy. Planting in heavy clay is a no-no: root rot often ensues, indicated by yellowing, wilting foliage and collapse of the plant. Planting in limy, alkaline soil is another mistake; lack of iron quickly results in chlorosis (yellow leaves with green veins). Alkaline soil has not, however, discouraged azalea lovers in Texas and Oklahoma. The recommended practice there is to build raised beds 15–18 in. deep and fill them with a half-and-half mixture of finely milled bark and coarse sphagnum peat moss (be sure to mix the two thoroughly with water before filling the beds). Irrigating with alkaline water will slowly raise the pH; to keep it in the desired range of 5.0–6.0, prepare a mixture of 3 parts garden sulfur to 1 part iron sulfate, then apply it at the rate of 1 pound per 100 sq. ft. of garden bed. This should lower the pH by one point.
Plant azaleas and rhododendrons with the top of the root ball slightly above soil level. Don’t cultivate around these plants, as they have shallow roots. Because they absorb water through their foliage, wet both the leaves and root zone when you water. Overhead watering with sprinklers works well, but to prevent fungal diseases do this in morning so that leaves dry by afternoon. Avoid drip irrigation―it doesn’t wet the root system uniformly.
In spring, just after the blooms fade, apply mulch and fertilize with a controlled-release, acid-forming fertilizer such as cottonseed meal or commercial azalea/camellia food. Do not mulch in fall; this will hold heat in the soil and delay the onset of dormancy, increasing the chances of winter damage. And don’t fertilize before bloom―you’ll encourage leafy growth at the wrong time.
The sun tolerance of azaleas and rhododendrons varies by species and selection. In general, most types prefer the partial sun or filtered shade beneath tall trees. The east and north sides of the house are better locations than the west and south. Too much sun bleaches or burns the leaves; too little results in lanky plants that don’t bloom.
Insects and diseases seldom bother healthy, vigorous plants. However, rhododendrons growing in heavy clay often fall victim to Phytophthora, a deadly soil-borne fungus that causes dieback. Azaleas growing in full sun are often plagued by sucking insects called lace bugs. For solutions to both problems, see the Southern Living Garden Problem Solver.
The rhododendrons listed here are all evergreen; azalea species and hybrids may be evergreen or deciduous. Plant sizes vary somewhat within groups, but most individual plants are roughly equal in height and width.
Pruning rhododendrons is simple―just follow these general guidelines. Tip-pinch young plants to make them bushy; prune older, leggy plants to restore shape by cutting back to a side branch, leaf whorl, or cluster of latent buds. Do any extensive pruning in late winter or early spring. Pruning at this time will sacrifice some flower buds, but the plant’s energies will be diverted to latent growth buds, which will then be ready to push out their new growth early in the growing season. You can do some shaping while plants are in bloom; use cut branches in arrangements. To prevent seed formation, which can reduce next year’s bloom, clip or break off spent flower trusses, taking care not to damage growth buds at base of each truss.
Evergreen azaleas are dense, usually shapely plants; heading back the occasional wayward branch restores symmetry. To keep bushes compact, tip-pinch frequently, starting after flowering ends and continuing until mid-June. Prune deciduous azaleas while they are dormant and leafless. You don’t have to prune azaleas as carefully as you do rhododendrons―the leaves are fairly evenly spaced along the branches, with a bud at base of each leaf, so new growth will sprout from almost anywhere you cut (in either bare or leafy wood).
Kinds of Rhododendrons
Most people know rhododendrons as big, leathery-leafed shrubs with rounded clusters (“trusses”) of stunning white, pink, red, or purple blossoms. These are primarily hybrids of catawba rhododendron, R. catawbiense, which is native to the Appalachians. But there are also dwarfs just a few inches tall, giants that reach 40 ft. or even 80 ft. in their native Southeast Asia, and a host of species and hybrids of intermediate size. Hybrids with Asian parentage may display exotic colors of yellow, apricot, and salmon; unfortunately, plants with these colors are often less tolerant of the South’s summer heat.
The following sections place named selections in categories to help you decide whether they’re suited to your garden and how to employ them.
Vireyas for indoors and frost-free areas. The Vireya rhododendrons, from the tropics of Southeast Asia, manage nicely in frost-free and nearly frostless zones. They are also fine container plants (even indoors), so they can be grown in colder zones if brought inside for the winter. They need an especially fast-draining potting mix (many species are epiphytes in the wild); a combination of equal parts peat moss, ground bark, and perlite works well. Typically, plants flower on and off throughout the year rather than in one blooming season. They bear waxy-textured blossoms in exciting shades of yellow, gold, orange, vermilion, salmon, and pink, plus cream, white, and bicolors. Species, named hybrids, and unnamed seedlings are offered by some specialty growers.
Rhododendrons in Clay or Alkaline Soil? They don’t like it. Planting in raised beds that are 1–2 ft. above the original soil level is the simplest way to give these plants the conditions they need. Liberally mix organic material into top foot of native soil, then fill bed above it with a mixture of 50 percent organic material, 30 percent soil, 20 percent builder’s sand. This mixture will hold air and moisture while allowing excess water to drain.