Evergreen Azalea Hybrids and Species
A genealogical study of the 503 varieties and species grown at Sonoma Horticultural Nursery
All evergreen azaleas we carry are classified into the Rhododendron subseries obtusum. Of the the 20 known species, all are native to Eastern Asia. These are the parents of the hybrid groups below.
BELGIAN INDIAN (INDICA) (BI) HYBRIDS
Developed from R.simsii and possibly R.indicum in Belgium for greenhouse-forcing in the mid 1800's. Not so cold hardy (Zones 8-9). They form medium-sized shrubs, 4'-6' high, well-branched and spreading with medium-sized leaves. Floriferous habit. Blooming ranges from early to mid-late season.
The American equivalent of BI Hybrids. Developed in the 1920's in New Jersey as greenhouse forcing azaleas. Hardy in Zones 8-9. Medium-sized shrubs, 4'-6' high, spreading, compact, and floriferous. Colors range from reddish orange, to purple and white. Many are frilled.
Developed in Modesto, California using some Southern Indian and Kurume Hybrids. Hardy in Zone 8. Medium-sized, to 4'-6' tall. Bloom time: mid-season to late.
Another group developed in California, resulting in forcing azaleas that are more adaptable for landscaping. Some show their BI parentage, while others are Kurume type. Upright habit, 3'-5' tall. Hardy in Zone 8.
-CORAL MAY QUEEN
-----MOSSHOLDER-BRISTOW HYBRIDS aka: GOLD CUP AZALEAS
From California, these are fourth generation hybrids, derived from BI hybrids and Rutherford hybrids for greenhouse forcing, but are quite hardy to cold (Zone 8). Medium-sized shrubs, 4'-6' tall.
SOUTHERN INDIAN (INDICA) (SI) HYBRIDS
This hybrid group was developed from a large collection of Belgian Indian hybrids in the Southeastern US around 1870. It is a mixed group, including forms and hybrids of R. indicum X R. simsii and 'Mucronatum' forms X R. indicum. Early bloomers are usually more upright and vigorous, while later bloomers are more compact and spreading. This group is sometimes referred to as "Sun Azaleas" because of their strong sun and heat tolerance. Hardy in Zones 8-10.
-DUC de ROHAN
-GEORGE LINDSEY TABER
-PRIDE OF DORKING
-PRIDE OF MOBILE
This large group of azaleas has a long and complex history. For over 300 years, the Japanese have hybridized the Kirishima Azalea (R.X'obtusum') and at one time, there were as many as 700 different cultivars. Once thought to be derived soley from R.kiusianum found on Mt. Kirishima in Japan, further research has shown that there are two more species involved; R.kaempferi and R.sataense; as well as one naturally occurring hybrid: R.x'obtusum'. All three are found on the surrounding mountains, where they freely hybridize with each other, producing groups which strongly resemble the Kurume Hybrid Azalea in flower and form. These groups show strongest alliance to R.sataense, not R.kaempferi and R.kiusianum as previously believed.
In 1915, at the Panama Pacific Exposition in San Francisco, Kurume Hybrids were introduced to the Western World. Over the next decade, thousands of new types were introduced from Japan. Unfortunately, English names (not translations) were substituted for the Japanese ones, wiping out all records of the original names.
Upright, compact growth habit (many are twiggy with reddish-hued stems and smaller foliage much like R.kiusianum). Early to early midseason flowers, mostly single with some hose-in-hose, ranging in size from 1/2" to 1 1/2" wide. Full range of colors from pink, red, purple and white, with some striped or flecked flowers. They are quite hardy to cold (Zones 7-8) and most are sun tolerant.
We grow 80 varieties. Related groups include:
Over 10,000 seedlings were grown for eight years in South Carolina. Six were later selected as the best for hardy, greenhouse-forcing azaleas. We grow the one named for the hybridizer's four daughters: POlly, SAlly, EMmie, and ANn.
-----BELTSVILLE (YERKES-PRYOR) HYBRIDS
These were produced by the U.S.D.A. in Maryland starting in 1950. Good cold hardiness (Zones 7-9).
True genetic dwarfs, selected from the above group. Early bloomers with a very low, compact, spreading habit and normal-sized flowers which cover the plant in bloom.
Introduced around 1947 from Maryland. R.y.var.poukhanense was used as part of the seed parent. They bloom early to midseason, and are medium to tall, compact plants. Hardy in Zones 7-9.
From Pasadena, California, this group was introduced in the 1930's. Some have R.'Mucronatum' parentage. Hardy in Zones 7-9.
This group was started in Pennsylvania in the mid 1930's to be used for greenhouse forcing, but shows hardiness in Zones 7-9.
Developed around 1885 in Massachusetts from some of the first evergreen azaleas to be introduced to the U.S. Many are now lost. The 'HEXE' cross was also done in Austria at the same time, where it was used extensively as a stock plant to graft Indidan Azaleas.
R.kaempferi, from the mountains of Japan, was first introduced by the Arnold Arboretum in 1892. It proved hardier than the Kurume Azalea on the east coast. Here, it was extensively hybridized, reaching a peak in the late 1920's.
The original Kaempferi Hybrids are mostly medium to tall shrubs (4' or more), with flowers 1 1/2" to 2 1/2". Colors range from pinks to reds and purples, with a few whites. Some of the red or orange types may fade in too much sun. Some show excellent fall and winter color. Hardy in Zones 6-9. They may loose some leaves in very cold weather.
These were produced in Pennsylvania, using mostly R.y.var.poukhanense and R.kaempferi, resulting in some of the hardiest evergreen azaleas available (Zones 6-9).
Looking to produce compact, hardy evergreen azaleas for use in landscaping and containers, this group was started in the late 1940's in Ohio.
This group was started in the 1950 in New Jersey with greenhouse-forcing azaleas in mind. By 1953, breeding was focusing more on plant habit and form, as well as cold tolerance. Hardy parents included Kurume and Kaempferi Hybrids plus some Indian Hybirds.
-GARDEN STATE GLOW
-GARDEN STATE SALMON
-GARDEN STATE WHITE
From Ohio, this group bears some similarity to the Gable Hybrids. They are extremley hardy to cold (down to -15oF in Zone 5).
Developed in Holland starting in 1921, this is a hardy group with large flowers.
-VUYK'S DOUBLE BEAUTY
For several centuries, the Japanese have held this group of evergreen azaleas in the highest regard, developing many hundreds of different cultivars, giving this group the greatest range in flower, foliage, and form of all evergreen azaleas. Those derived primarily from R.indicum and/or R.tamurae (R.eriocarpum), with some other species in the mix, are considered Satsuki Azaleas.
In early June, festivals and exhibitions take place in parts of Japan to celebrate the Satsuki. In its use in Japanese gardens, flower display may play a secondary role, for foliage and form are also very important. They may be sheared to resemble rocks and many are used for Bonsai work. Their small leaves and their purple-red tones in winter are considered essential elements to the Satsuki group.
Satsukis were first introduced to the Western world in the early 1900's with major introductions coming in the late 1930's. They are late bloomers, usually late May into June. The flowers are generally single, although there are a few hose-in-hose, semi-double, and doubles. There is a great variation in petal structure as well as flower color. There can be solid tones, stripes, flecks, and sectors in different shades - all on the same plant. Japanese books may describe 12 or more color patterns. Most are slower-growing, compact, spreading plants. They are hardy in Zones 7-9. Because of their late blooming habit, it is best to give them some protection from the hot, mid-day sun.
We grow 80 varieties as well as the following clones:
These are relatively new groups of evergreen azaleas, starting with the introduction of the Glenn Dale Hybrids in the late 1940's. At least 75% of the azaleas introduced in the past 30 years are inter-group hybrids, using Satsuki, Kurume, and Kaempferi Hybrids, as well as other groups.
-----AUGUST KEHR HYBRIDS
From North Carolina, this group was started in the early 1960's looking to produce low-growing plants with double flowers and good cold hardiness (down to 0oF).
-----CARLA HYBRIDS aka: N.C.S.U. HYBRIDS
This breeding program began in 1965 at North Carolina State University. The goal was to produce greenhouse-forcing azaleas with mostly double flowers that opened simultaneously. This group is also disease-resistant and cold hardy.
-----GLENN DALE HYBRIDS
Starting in 1935 at the National Arboretum in Glenn Dale, Maryland, an extensive hybridizing program was undertaken with several objectives in mind: To develop plants with flowers as large and varied as the Southern Indians but with good cold hardiness, and to produce varieties that would bloom from late April to June to fill the mid-May flowering gap that was then typical of evergreen azaleas. Over 70,000 seedlings were started, with 440 clones introduced in the 1940's.
The Glenn Dale Hybrids represents a full range in flowers, foliage, form, and bloom times. Those species used in breeding include R.indicum, R.simsii, and R.y.var.poukhanense, as well as the Satsuki, Kaempferi, Kurume, and Southern Indian Hybrids. They are hardy to -10oF in Zones 6-9.
We carry 58 varieties.
From Canby, Oregon, this group was started in 1960 to develop compact plants for moist, temperate climates. Most have single flowers and are hardy to 0oF.
Begun in 1970 in Lawrenceville, Georgia, this group has large flowers that bloom late-mid-season. Hardy in Zones 7-9.
-PRIDE OF LAWRENCEVILLE
-----LOBLOLLY BAY HYBRIDS
From Maryland, this group was selected from seedlings of Glenn Dale Azaleas. Hardy in Zones 6-9.
-GEISHA #2 (GEISHA, TOO)
Developed in the late 1970's in Virginia for greenhouse-forcing and container culture, this group is hardy in Zones 8-9.
-----NORTH TISBURY HYBRIDS
From Martha's Vineyard in Massachusetts, beginning in the 1960's, this group was created from seed and cuttings sent from Japan. Many show R.nakaharai heritage with their low-mounding, spreading habit and cold hardiness (Down to -5oF).
This group comes from Altadena, California. Since the mid 1930's, an extensive breeding program has produced a wide range of evergreen azaleas. This nursery is also well-known for its work with Camellias.
-NUCCIO'S CARNIVAL QUEEN (BI type)
-NUCCIO'S DEW DROP
-NUCCIO'S EASTER DELIGHT
-NUCCIO'S GARDEN MAGIC
-NUCCIO'S HAPPY DAYS (BI type)
-NUCCIO'S HIGH SIERRA (Kurume type)
-NUCCIO'S IVORY TOWER (Kurume type)
-NUCCIO'S LITTLE GEM (Kurume type)
-NUCCIO'S LITTLE RED RIDING HOOD (Kurume type)
-NUCCIO'S MELODY LANE
-NUCCIO'S MT. BALDY (Satsuki type)
-NUCCIO'S PINK BUBBLES (BI type)
-NUCCIO'S PINK SNOW
-NUCCIO'S PLUM PURTY (Kurume type)
-NUCCIO'S TREASURE CHEST (BI type)
-NUCCIO'S WILD CHERRY (Satsuki type)
Developed in Pennsylvania, this group was first exhibited at the Philadelphia Flower Show in 1931. Used mostly for greenhouse-forcing, they also show good cold hardiness (Zone 7-9) with their Kurume parentage.
-----ROBIN HILL HYBRIDS
Started in 1937 in New Jersey to produce hardy, late blooming azaleas resembling Satsukis, this group blooms late season and is hardy in Zones 6-9.
-MRS. EMIL HAGER
-NANCY OF ROBIN HILL
-ROBIN HILL GILLIE
This group was developed in the 1960's and 1970's by Mr. Stewart Barber, the original owner of SHN. Most of the information on the crosses has been lost. The Sonoma Dwarf series was developed from Satsuki seed sent from Japan and were introduced in 1974 by color.
-MRS. GARNET KYMPTON
-nakaharai X 'DEEP SALMON'
-nakaharai X 'MEDIUM PINK'
-nakaharai X RUKIZON
-SONOMA DWARF 'PINK'
-SONOMA DWARF 'PINK PICOTEE'
-SONOMA DWARF 'ROSE REDWOOD'
-SONOMA DWARF 'VERMILLION'
From Yokohamashi, Japan, this group is closely related to the Satsuki group.
MISCELLANEOUS INTER-GROUP HYBRIDS
-CORAL DOGWOOD (sport of DOGWOOD)
-HOT SHOT VARIEGATED
-PEARL BRADFORD SPORT (sport of PEARL BRADFORD)
-SHIRO CHAN VARIEGATED
AZALEODENDRONS (HARDIJZER HYBRIDS)
Developed in Boskoop, Holland, and first registered in 1958, this group is technically a distinct hybrid subgenus and not "true" azaleodendrons. They are evergreen with small, clustered flowers.
-HARDIJZER'S BEAUTY (R.racemosum x Kurume Hybrid)
-MARITIME (MARTINE) (R.racemosum x Kurume Hybrid)
-RIA HARDIJZER (R.racemosum x Hinode Giri)
-----listed with evergreen azaleas:
-indicum (syn. macrantha)
-macrogemmum '77-642 RSF' (may be a var. of R.kaempferi)
-macrosepalum 'LADY LOCKS' (also 'Linearifolium' & 'Koromo shikibu')
-mucronatum & forms (should be in SI hybrids with R.mucronatum clones)
-noriakianum '78-036 RSF'
-pianensis '79-088 RSF'
-tamurae (syn. eriocarpum)
-yedoense var.poukhanense (syn.poukhanense)
-----listed as rhododendrons:
-kiusianum (20 varieties)
-linearifolium (should be a var. of R.macrosepalum)
-nakaharai (4 varieties - Mt. Seven Star a North Tisbury Hybrid)
-serpyllifolium (3 varieties)
----- 202 Hybrids listed here by group
----- 58 Glenn Dale Hybrids
----- 80 Kurume Hybrids
----- 150 Satsuki Hybrids
----- 13 species & their forms
503 Evergreen Azaleas