Azaleas

      
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Azaleas

Azaleas are often considered as distinct from other rhododendrons and in fact formed a separate genus from 1753 to 1796. Azaleas are divided into two groups: Deciduous Azaleas and Evergreen Azaleas.

Azaleas

Subgenus Description
Members
Azaleastrum evergreen azaleas & deciduous azaleas
45 evergreen azaleas & 6 deciduous azaleas
Hymenanthes elepidotes rhododendrons & deciduous azaleas
20 deciduous azaleas & (199 elepidotes)

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Azaleas are shrubs of the genus Rhododendron and members of the heath family. There are 8 divisions of the genus Rhododendron. Azaleas comprise one of those divisions and part of another. Technically classified as rhododendrons, azaleas are generally more floriferous than other rhododendrons, but have less impressive foliage. Typically other rhododendrons are evergreen and have flowers that are in trusses (a truss is a flower-like structure composed of many flowers). Typically an azalea is either evergreen with flowers singly rather than in a truss or are deciduous and may have flowers singly or in a ball-shaped truss.

When Linnaeus created the botanical grouping called genus Rhododendron in 1753, he created a separate genus for Azaleas containing 6 species. In 1796 Salisbury pointed out that Azaleas and Rhododendron could not be maintained as distinct genera. In 1834, George Don subdivided the genus Rhododendron into 8 sections. Azaleas comprised two of these sections.

Although azaleas have been considered to by part of genus Rhododendron since 1796, American and British horticulturists prefer to keep the two separate and most people familiar with rhododendrons and azaleas have no trouble keeping the distinction alive. Despite this artificial distinction, hybridizers have long known that deciduous azaleas are more likely to hybridize with elepidote rhododendrons than evergreen azaleas. The very first hybridized rhododendron, R. 'Hybridum,' was between deciduous azalea, R. viscosum, and the elepidote rhododendron, R. maximum.

The two sections of Genus Rhododendron comprised of Azaleas are: Subgenus Pentanthera typified by deciduous Rhododendron nudiflorum and Subgenus Tsutsusi typified by evergreen Rhododendron tsutsusi.

  1. If flowers grow from terminal buds, new leaves and shoots grow from lateral buds and leaves are deciduous, then the rhododendron is an azalea in the Pentanthera Section of the Hymenanthes Subgenus.
  2. If flowers and leaves grow from the same terminal buds, and the flowers have 5 to 10 stamens, then the rhododendron is an azalea in the Azaleastrum Subgenus.

In 2004, Goetsch, et. al. rearranged these 8 subgenera into 5 subgenera. Today, azaleas are grouped into the Pentanthera Section and Azaleastrum Subgenus.

Most azaleas grow in damp acid soils of hills and mountains, and are native to North America and Asia. Native American azaleas include the flame azalea (R. calendulaceum) and the fragrant white azalea (R. viscosum), also called swamp honeysuckle. Most of the brilliantly flowered garden varieties are from China and Japan. Some have deciduous leaves and are usually very hardy, while other are evergreen and frequently less hardy. The deciduous varieties are usually hard to propagate, but much progress had been made in this area. Evergreen varieties are usually easy to propagate. Many hybrid and species azaleas are in the commercial trade. They typically bloom early in the season and are popular for the color they add to the landscape.

One term that is used in describing many azaleas is hose-in-hose. This term is meant to describe what looks like a flower inside a flower. This actually is a flower with a large calyx. The sepals of the calyx are shaped like the petals of the corolla.

Another term that is more common with azaleas is double. A double flower looks like the interior is filled with petals. This is because the stamens grow into petal-like structures. The pistol may also be transformed into a petal-like structure or may be absent.

Another term is semi-double. In this case the stamens are partially transformed into petal-like structures. Occasionally extra petals are present and all stamens are present also.

Another version is hose-in-hose double. A perfect example of this is Gable's Rosebud azalea. The name is descriptive of the flowers appearance.

There are 18 species of azaleas that are native to North America.

Examples of Deciduous Azalea Species from subgenus Azaleastrum

 

Examples of Deciduous Azalea Species from subgenus Hymenanthes

 

Examples of Evergreen Azalea Species from subgenus Hymenanthes

 

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Azalea Deciduous Azalea Species from the Subgenus Azaleastrum

R albiflorum
 
R schlippenbachii
 
R vaseyi
 

R. albiflorum - 3', -25F. The Cascade Azalea is an upright, white-flowering, deciduous azalea that is widespread and common near flowing water in many forested mountainous areas of western North America from 4,000 to 7,200 ft. It is found in from British Columbia and Alberta to Oregon and Colorado near the timberline. An extremely unusual and quite unique species unrelated to any other, it is a difficult and rare species in cultivation, requiring excellent drainage and a cool but bright position. It does not do well in cultivation except in Scotland.

R. schlippenbachii - 4', -20F. The Royal azalea is a deciduous Korean species. It has soft green leaves that grow in whorls around the stem and turn yellow, orange and crimson in the fall. It is so lovely that man can hardly hope to improve upon its soft pink flowers. They are 3 inches across, and freckled on the upper petals and have a delicate fragrance. Schlippenbachii tolerates less acid soils in Zones 5-8 than the other species. It is hardy to -10° F and grows to 6 to 10 feet tall. [Return to Azalea Species Index]

R. vaseyi - 4', -15F. The Pinkshell Azalea is a medium to tall deciduous azalea found in North and South Carolina. It grows best in the moist soil bordering ponds in Zones 5-8, hardy to -10° F, where they grow 6 to 8 feet tall and bears 1 1/2-inch pink flowers in late spring to early summer. It also has a white variation. It has showy fall foliage when the willow-like leaves turn yellow and red. Discovered by George Vasey in 1878, this native azalea has a relatively restricted natural habitat in four mountainous counties of North Carolina. Growing at elevations of 3000 to 5500 feet, the rare Pinkshell azalea can be seen in bloom along the Blue Ridge Parkway in early spring. [Return to Azalea Species Index]

Deciduous Azalea Species from subgenus Hymenanthes

R alabamense
 
R arborescens
 
R atlanticum
 
R austrinum

R. alabamense - 4', -5F. The Alabama Azalea is a deciduous azalea found in Alabama and adjacent states. It has snowy white flowers with a prominent yellow blotch. Blooming in midseason, the flowers have a distinct lemon-spice fragrance and measure .8 to 1.5 inches across. Originally thought to be a white form of R. periclymenoides (R. nudiflorum), this plant was first described by Dr. C. Mohr in 1883. It grows naturally in north central Alabama, and western to central Georgia and South Carolina. R. alabamense is low to medium in height, and spreads by underground stems or stolons. It propagates with relative ease from soft wood cuttings and makes a delightful landscape plant.

R. arborescens - 5', -15F. The sweet or smooth azalea grows 4 to 6 feet tall and bears clusters of very fragrant 2-inch white or rose-tinged flowers in midsummer. Its leaves turn a deep glossy red in autumn and is hardy in Zone 5 to -15° F. It is a deciduous azalea found from Pennsylvania south to Georgia and Alabama. It is a good late flowering, scented species that can be used in cultivation. It has white to blush pink flowers with red stamens, and a very strong fragrance similar to heliotrope. It blooms in late spring to early summer and individual flowers measure 1.5 to 2 inches across. First described by John Bartram in 1814, this species has a wide distribution in the eastern United States, but can usually be found growing near streams or moist areas. It is sometimes known as the "Smooth Azalea" because the stems are very smooth and do not have hairs similar to the other azaleas. An excellent landscape plant, R. arborescens can perfume a wide area when in bloom. Relatively easy to propagate, there are a number of excellent forms in the trade.

R. atlanticum - 3', -15F. The Atlantic Azalea or Coastal Azalea is a low deciduous azalea found on coastal plains from Pennsylvania and Delaware south to Georgia. It is a good late flowering, scented species that can be used in cultivation. It is a common understory plant along the southeastern coastal plains of the United States. The white flowers are 1 to 1.5 inches across, but are often blushed with pink on the outside and some have a yellow blotch. Collected by John Clayton in 1743, this plant was appreciated more in England than in its native land. The plant habit is relatively low but stoloniferous. Spreading by underground stems, R. atlanticum can develop into very large colonies of an acre or more in sandy soils. R. atlanticum is easy to propagate, and makes a nice landscape plant in heavier soils that will restrict the spreading habit.

R. austrinum - 5', -5F. The Florida Azalea is a deciduous azalea found from northwest Florida to Georgia, Alabama and southeast Mississippi. This plant blooms in early spring as the leaves are beginning to expand. The fragrant blossoms come in shades of orange through gold and yellow, and measure approximately 1 to 1.5 inches across. This species has very long stamens and the tube of the flower is often flushed with red but there is no blotch. Discovered by Dr. A. W. Chapman before 1865, R. austrinum is similar in many respects to R. canescens including the sticky glandular hairs on the flower tube, but differs in the color variations which are orange to yellow rather than pink to white. R. austrinum makes an excellent landscape plant as well as a valuable hybridizing resource, especially in southern gardens where heat tolerance is important. [Return to Azalea Species Index]

More Deciduous Azalea Species from subgenus Hymenanthes

R calendulaceum
 
R canadense
 
R canescens
 
R colemanii

R. calendulaceum - 6', -10F. The Flame Azalea is one of the most brightly colored of native North American shrubs, bearing large clusters of 2-inch flowers in early summer. Plants usually grow 4 to 9 feet tall in Zones 5-8, hardy to -10° F, and occasionally reach 15 feet. It bears clusters of 2-inch clove-scented bright scarlet, orange or yellow flowers in late spring or early summer flowers that are long lasting, even in full sun. The leaves are 3 inches long and drop in the fall.

R. canadense - 2', -25F. The Rhodora Azalea is a low deciduous azalea found from Eastern Quebec to Newfoundland and Nova Scotia, and south the northern parts of Pennsylvania and New Jersey. It has showy lavender flowers. It has a white form that comes true from seed. It does well in moist acidic soils. Rhododendron canadense is a very unusual native azalea species and was originally considered an entirely separate genus, Rhodora. The top three petals of the flower are fused together almost to the end to form a single lobe, whereas the bottom two are completely separate lips. The purplish pink blossoms are approximately 1.5 inches across and have 10 stamens, twice the number of most east coast natives. First described by Linnaeus in 1762, R. canadense is a low stoloniferous shrub that is the most northern of the east coast native azaleas, the species is very cold hardy but a difficult plant where summers are hot and dry.

R. canescens - 5', -5F. The Florida Pinxter or Piedmont Azalea is often confused with R. periclymenoides. Both are medium deciduous azaleas that are found in the Carolinas but can be separated by the flower tubes, which in R. periclymenoides are fuzzy. R. canescens also has tiny hairs, but they are sticky and glandular. Another noticeable difference is that when a flower of R. periclymenoides dies, a ridge on the corolla tube tends to catch on the end of the pistil so that a flower cluster past its prime consists of several dangling blossoms. Although widespread in the eastern half of the U.S., these two wild azaleas differ in distribution. In South Carolina, for example, R. periclymenoides is a Piedmont plant, with almost no specimens reported from the Sandhills or Coastal plain, while R. canescens is predominantly a Low Country plant absent from the Piedmont, except in counties that border the Savannah River. In general, if it grows wild north of South Carolina, it's likely R. periclymenoides; south of the Palmetto State and it's probably R. canescens. Both species prefer moist, humus-laden, acidic soil but seem to do equally well in shade or sun. Old specimens can reach heights of 12-15 feet and have multiple stems or trunks up to 5" in diameter. Rhododendron canescens was discovered by Mark Catesby, who published a picture of it in 1731. Michaux collected it in South Carolina between 1784 and 1796. It was probably introduced to England in the mid-eighteenth century.

R. colemanii - 6', -5F. The Red Hills Azalea, from the upper Coastal Plain of Alabama and Western Georgia, was named in 2008. It was initially collected and propagated by S. D. Coleman, Sr. It is one of the tallest, most fragrant and most richly colored of all the native azaleas. Different plants may show flower colors ranging from pure white to deep pink, and even yellow or nearly orange. It's also late blooming, typically flowering in early May. In the field, the azalea can be distinguished from R. alabamense and other coastal azaleas by its late spring (early to mid May) flowering time, its wide range of flower color (white, pink or yellow), longer flower buds, its often warty seed capsules with glandular hairs, and its taller stature (3-7 m). Its natural distribution extends from southwestern Alabama to the Chattahoochee Valley in Georgia. [Return to Azalea Species Index]

More Deciduous Azalea Species from subgenus Hymenanthes

R cumberlandense
 
R eastmanii
 
R flammeum
 
R luteum

R. cumberlandense – 4', -15F. The Cumberland Azalea is a low deciduous azalea found in Kentucky, Virginia, Tennessee, North Carolina, Georgia and Alabama. It has long been grown under the name, R. bakeri. It is an excellent, low-growing, late blooming orange to red-flowered azalea suitable for small gardens. The flowers are not large, about 1.5 to 1.75 inches across, and typically range from yellowish-orange to deep red. This species is sometimes difficult to distinguish from the larger flowered R. calendulaceum, but the blossoms generally appear several weeks later after the leaves have fully expanded and the undersides of the leaves are usually waxy white or bluish in color. Lemon and McKay first described the species distinction for R. cumberlandense in 1937. This native azalea makes an excellent landscape plant in its own right, but it also hybridizes easily with many of the other species, producing beautiful hybrids in a broad range of colors.

R. eastmanii - 3', -15F. The May White Azalea is a deciduous azalea found in South Carolina in 13 counties of the piedmont and coastal plain to date, officially named, described and proposed as a new species in Novon in September of 1999. It has snowy white flowers with a prominent yellow blotch. Blooming in mid May, the flowers have a distinct, strong, fresh fragrance and measure .8 to 1.5 inches across. Originally thought to be R. alabamense, this plant was first described, noticed and thought to be different from known S.C. species by Charles Eastman in the early 1980s, one hundred years after Dr. C. Mohr discovered R. alabamense. R. eastmanii is low to medium in height, and has a clump habit but does not spread by underground stems. It propagates with relative ease from woody cuttings and makes a delightful landscape plant.

R. flammeum - 3', -5F. The Oconee Azalea (synonymous with R. speciosum) is a deciduous azalea found in the lower Piedmont from central Georgia to South Carolina. It is seldom cultivated in cooler climates but does well in the southeast. Its blossoms are approximately 1.2 to 1.8 inches across and come is shades of yellow, yellow-orange or red. This species can be distinguished from the earlier blooming R. austrinum in that the flowers usually have a large yellow blotch on the top lobe (petal), they are not fragrant, nor do they have sticky glandular hairs on the corolla tube. R. speciosum was collected by Michaux on April 26 and 27, 1787 near Two Sisters Ferry on the Savannah River described in his 'Flora' as A. callendulacea v. flammea. Several other early collections were also made of this species. Sweet assigned the name R. speciosum in 1830. Plants of this species were described by Aiton at Kew Gardens in 1789 and were probably sent there by William Bartram prior to that date. This species is a heat tolerant shrub and holds much breeding potential where hot summer stress is a problem.

R. luteum - 4', -10F. The Honeysuckle Azalea is a species of Rhododendron native to southeastern Europe and southwest Asia. In Europe, it occurs from southern Poland and Austria south through the Balkans and east to southern Russia, and in Asia, east to the Caucasus. Despite the sweet perfume of the flowers, the nectar is toxic, containing grayanotoxin; records of poisoning of people eating the honey date back to the 4th century BC in Classical Greece. [Return to Azalea Species Index]

More Deciduous Azalea Species from subgenus Hymenanthes

R molleJ
 
R occidentale
 
R periclymenoides
 
R prinophyllum

R molle ssp. japonicum - 4', -15F. The Japanese Azalea is an upright, bushy shrub that is cold hardy down to -15 degrees F with small, oblong leaves turning red in autumn. The orange-red flowers are borne in large, showy trusses in mid-spring just before the leaves emerge and carry a sweet fragrance. In the 1800's many form of R. molle ssp. japonicum were found. These were called the Mollis Azaleas. Some were selected forms of R. molle ssp. japonicum and others were hybrids.

R occidentale - 5', -5F. The Pacific or Western Azalea is a tall deciduous azalea found in the Pacific Coast states. The flower color is usually white or pale pink with a strong yellow flare, but may be red, yellow or orange-pink and occasionally the flare is maroon. The foliage turns red and copper shades in the fall. It is among the showiest of all species with bright colors on impressive flowers. However it is difficult to propagate and grow. It is considered impossible to grow on the East Coast. Rhododendron occidentale is the only native azalea that grows naturally west of the Rocky Mountains in the United States. William Lobb, a collector for Veitch and Sons of Exeter, is credited with having introduced R. occidentale to England in 1850.

R. periclymenoides - 5', -15F. Formerly R. nudiflorum, the Pinxterbloom Azalea is a medium deciduous azalea found from Vermont and Massachusetts south to South Carolina and north Georgia and Alabama and west to Tennessee and Ohio. It has showy pinkish-white flowers. Pinxter-flower, with lightly fragrant inch-wide blooms, is perhaps the most common and most familiar wild azalea in the eastern U.S. The name "pinxter" comes not from its coloration but from the Dutch words Pinxter blomachee, which relate to the fact that this is supposedly the azalea that blossoms on Pentecost, 50 days past Easter. We suspect this name was given by folks in northern parts of the plant's range, since in the Carolinas it is more likely to be in bloom for Easter Sunday itself. R. periclymenoides, was probably discovered by John Banister. Plunkenet described it as "Cistus virginiana pericyclemeni flore ampliori et minus odorato". Peter Collinson who received it from John Bartram in America and introduced to England between 1725 and 1730.

R. prinophyllum - 5', -25F. Formerly R. roseum, the Early Azalea is a medium deciduous azalea found from southwestern Quebec, through New England, to Appalachian Mountains in Oklahoma and Arkansas at the higher elevations. The flowers are typically rose pink measuring 1.2 to 1.8 inches across and are very fragrant. Assumed to be a form of R. periclymenoides (R. nudiflorum) since its first mention in 1787, it was first described as a distinct species in 1914 by Small but had been under cultivation as A. rosea in Europe before 1812. R. prinophyllum can be distinguished from R. periclymenoides by a number of characteristics including the fact that it is usually deeper pink in color and with a strong cinnamon to clove fragrance. R. prinophyllum is a good landscape plant for northeastern gardens, but may be more difficult in the south because of summer heat.

[Return to Azalea Species Index]

More Deciduous Azalea Species from subgenus Hymenanthes

R prunifolium
 
R viscosum
       

R prunifolium - 4', -10F. The Plumleaf Azalea is a medium deciduous azalea found on the Georgia-Alabama border. The color ranges from orange-red to red, and occasionally orange or yellow. The petals have a deep red blotch. This species blooms very late, usually in late June or in July. Plants are usually 5 to 8 feet tall, although some mature plants may attain a height of 20 feet. First collected by R.M. Harper in 1913, R. prunifolium prefers more shade than most deciduous azaleas to prolong the flowers during hot summer months. It is the signature plant of Callaway Gardens in Pine Mountain, Georgia.

R. viscosum - 6', -20F. The Swamp Honeysuckle or Swamp Azalea is a medium deciduous azalea found in low areas along stream banks from Maine to Georgia and west to Texas. Rhododendron viscosum now includes two closely related forms that were previously considered separate species, R. serrulatum and R. oblongifolium. The fragrant flowers with a clover-like fragrance are generally white to pale pink, and bloom after the leaves have fully expanded. Flowers vary in size from 0.75 to 1.5 inches across depending upon the form, but have a long narrow tube covered with sticky glandular hairs. It grows up to 9 feet tall and is hardy to -20° F. The leaves turn orange or bronze red in the fall. The species has a wide distribution from Maine to Florida, and westward to Texas. R. viscosum was the first North American azalea grown in England. It can be distinguished from the other late blooming white, R. arborescens in that the stamens are greenish white rather than red, and the stems are not smooth but contain hairs. R. viscosum is a variable species closely related to R. serrulatum, R. arborescens, R. oblongifolium, and R. atlanticum. These species are sometimes not easily distinguished from each other and have been frequently confused. Bishop Henry Compton raised the plant in 1680 from seed collected by John Bannister, an English missionary in eastern North America. John Banister sent a drawing of R. viscosum to Dr. Henry Compton, Bishop of London. Leonard Plundent published it in 'Phytographia' in 1692 after Banister's untimely death. The species was an important parent in early hybridizing efforts with deciduous azaleas. In1734, John Bartram, an American farmer-horticulturist, sent R. viscosum to Peter Collinson in England. [Return to Azalea Species Index]

Evergreen Azalea Species from subgenus Hymenanthes

R kiusianum
 
R macrosepalumL
 
 Rmucronatum
 
R yedoense

R. kiusianum - 3', +5F. The Kyushu azalea is a low-growing Japanese species, only 18 inches high. Its leaves are deciduous when the plant is young but evergreen in maturity, remaining on the plant all winter, though often changing color. In its original form the Kyushu azalea is covered in mid-spring with 8- to 10-inch clusters of lilac pink flowers, but there are many named hybrids derived from this species bearing white, pink, rose or purple flowers. It blooms while still young, bearing flowers 1 to 1 1/2 inches across. It is hardy in Zone 7, +5° F. This semi-evergreen spreading shrub grows 3 feet tall, but up to 5 feet wide. The shiny 1-inch leaves sometimes turn red in winter.

R. stenopetalum var. linearifolium - 4', -15F. The Spider azalea is an unusual Japanese species. It is a 4-foot-tall shrub with narrow, ribbon-like evergreen leaves, 3 inches long and 1/2 inch wide, and rose-pink flowers with deeply divided petals. It is hardy to Zone 5, -15° F. In one variety, R. linearifolium 'Macrosepalum', the plant is somewhat smaller, 3 feet tall, and the leaves are deciduous and 3 inches long. But the flowers are even more curiously shaped than those of the species; they have 1 1/4-inch-long sepals that overshadow the petals. The flowers of this variety are fragrant and have been bred in several colors; in one, 'Polypetalum', flower petals and leaves are so similar in size that the plant seems to have pink and green leaves.

R. mucronatum - 3', -5F. The Snow azalea has Chinese ancestry but is not found in the wild. It is commonly used for ornamental pruning, grows 6 feet high and 4 to 6 feet wide. It is hardy to Zone 5, -15 F. Its many branches are densely covered with oval evergreen leaves, 1 1/2 to 2 1/2 inches long, matted with hairs. Its fragrant white flowers, 1 to 3 inches wide, often bloom in pairs and may be stained with green, lilac or pink at the base, depending on the variety.

R. yedoense - 2', -5F. The Yodogawa azalea has 2-inch double reddish purple flowers in late spring. Although this plant is technically an evergreen azalea it is deciduous in cold climates. Plants rarely grow more than 3 feet tall, but may spread to 6 feet in diameter. It is hardy in Zone 6 to -5° F. The variety R. yedoense 'Poukhanense', Korean Yodogawa azalea, has single flowers and is a bit more resistant to winter cold than the double-flowered type. It is a low, spreading plant that is hardy to -15° F. The leaves of both drop in Northern gardens, but remain nearly evergreen in milder climates. [Return to Azalea Species Index]

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How To Grow Azaleas

Azaleas are alike in their need for moist well-drained, acid soil (pH 4.5 to 5.5) that has been well supplemented with humus such as peat moss or leaf mold. Azaleas will grow in full sun or light shade, but light shade is preferable in hot areas.

The most important factor in achieving vigorous growth is an acid soil mixture high in organic content. Many commercial growers set azaleas in pure peat moss, or in a 50-50 mixture of peat moss and coarse sand or perlite. A favorite mixture on the West Coast is 1/2 peat moss and 1/2 ground redwood, but in such mixtures, plants must be fed regularly.

Because the roots grow near the surface, a bed prepared especially for rhododendrons and azaleas need not be more than 12 inches deep; deep planting keeps the roots from getting the air they need. In fact, it is a good idea to set them about 1 inch higher than they grew at the nursery. Balled-and-burlapped plants may be transplanted in blossom but it is better to transplant them early in spring in areas where their hardiness is questionable, and in spring or fall where there is no likelihood of winter damage.

Cultivating the soil around azaleas would damage their roots. Instead, keep the roots cool and moist with a permanent 2- to 3-inch mulch of wood chips, oak leaves, chunky peat moss or other light organic material. Plants that have been given a soil mixture rich in organic matter probably will not need feeding for several years. Do not stimulate fast growth because it produces long weak stems and few flowers. But if a plant seems weak or sickly, use cottonseed meal or a special rhododendron-azalea-camellia fertilizer, dusted on the soil early in the spring. For maximum flower production, pinch off faded flowers or the seed capsules that follow.

Most evergreen azaleas may be propagated from stem cuttings. Most evergreen azaleas do not develop their full hardiness until after three seasons. In general, they need protection their first three winters after they are rooted. Normally, they will be grown in a protected area the first winter. Then they will be container grown in protected areas the second year. Then the third winter they will be field grown in a somewhat protected area. Then the fourth winter they should have reached their full hardiness.

Evergreen azaleas can be sheared for hedges or borders. Unlike rhododendrons, evergreen azaleas can be sheared each year after flowering to create a dense rounded plant. Highly trained Japanese gardeners prune evergreen azaleas extensively and with great results.

Deciduous rhododendrons are propagated by seed, grafting or cutting. Deciduous azaleas are very tricky to propagate from cuttings. Tissue culture is used to propagate varieties that are difficult to root. It is a laboratory technique that is very successful.

Take cuttings of deciduous azaleas when the new growth is soft and pliant. This is often coincident with time of bloom in early June. The ability to root decreases rapidly as new growth matures. Select cuttings daily for best results. Trim cuttings below a node (overall length of cuttings 3 to 5 inches) and dip in a root hormone containing fungicide. Insert in a medium of 60% peat moss and 40% horticultural perlite. Usually bottom warmth of 75°F is used to encourage root growth. In late August, transplant cuttings that are rooted and grow on in the greenhouse with supplementary light (14-hours a day) to prevent dormancy and induce new growth. In the fall after new growth has matured, transfer to a cool, frost-free cool (35°F to 41°F) environment to induce dormancy. As new growth develops in the spring, transfer plants to a shaded environment. [after "Rhododendrons and Azaleas" by J. Lounsbery, Horticultural Research Institute of Ontario, Canada]

Where soils are moist and naturally very acid, deciduous azaleas and rhododendrons thrive in partial shade, especially in hot areas, but grow reasonably well in full sun. The species and hybrids listed need very little pruning and seldom have serious infestations. Their foliage may turn to bright hues in autumn.

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