QBARS - v14n1 The Parentage of Hybrid Azaleas

The Parentage of Hybrid Azaleas
by Clark D. Paris
Department of Horticulture
Michigan State University*

*The author wishes to thank Prof. C. E. Lewis for his assistance in collecting this data.

In 1753 when the immortal Linnaeus described the genera Azalea and Rhododendron , he initiated a controversy which has continued for almost two centuries. Most taxonomists agree that any line of demarcation between these two genera is entirely arbitrary; yet in 1942, Lemmon and McKay described a new species as Azalea furbishii. Shakespeare said that "a rose by any other name would smell as sweet". In this paper all species of "azaleas" are considered of the genus Rhododendron .

Regardless of the validity of the genus Azalea , this name has been retained for a group of plants that are very popular wherever they can be grown successfully. The wild species have been cultivated since the seventeenth century. When the pioneer hybridizers began crossing species of plants, the azaleas were among the first with which they worked. As more rhododendrons were introduced, these were crossed with the existing varieties. Each breeder developed his own breeding objectives and worked towards them until definite races of hybrids became known. Usually these races were named for the originator or the place where he worked. A complete list of azalea hybrid groups, as well as certain pertinent data about each, is given in Table I. The introduction dates of the hybrids were obtained directly from the originators, or their descendents. A study of the parentage of hybrid azaleas has revealed that, as far as is known, only twenty-seven species have been used. These, with the native habitat, color, and year of introduction, are given in Table II. The nomenclature is that given by Lee (4). Rehder (6) relegates some of these to a varietal status. No attempt is being made to give the pros and cons of this debate.

The main purpose of this paper is to present a chart to show the parentage of the introduced hybrid azaleas. The horizontal line above the name of each hybrid connects with a vertical line from each species or hybrid that was used in the production of that particular group. Any one variety does not necessarily contain blood from all parents. A broken line is used if the parent is in doubt. The Southern Indian hybrids and double Ghent hybrids are selections from Belgian Indian hybrids and Ghent hybrids, respectively. The Shammarello hybrids are inbred selections of Mollis hybrids.

This chart is just as accurate as the sources of information used. Like all progeny or pedigree records the originator's information is accepted as prima-facie evidence. Although it is probably at a bare minimum the possibility of deliberate misinformation cannot be wholly discounted. Several other sources of error are possible. One of the more plausible is the misidentification of parent material. Most people do not systematically check the material with which they are working, and then too, the same name has sometimes been applied to different plants. The old practice of giving Latin names to hybrids adds to the confusion. Sometimes the originator did not keep adequate records and depended on memory. Another early practice was the mixing of pollen and then when something of value was obtained an attempt was made to postulate the pollen parent by studying the hybrid. A less obvious pitfall is apogamy. When the seed is produced without actual fertilization occurring. The seeds so produced actually contain only maternal tissue.

Table I
Introduced Hybrid Azalea Groups
Hybrid Group Originator Introduced
Abbott Frank L. Abbott, Bellows Falls, Vermont About 1943
Albican Anthony Waterer, Woking, Surrey, England About 1870
Allan* Walter Allan, Summerville, N. Carolina 1950
Amoena Various English growers 1860
Arends George Arends, Ronsdorf, Germany 1926
Arnold Jackson T. Dawson, Jamaica Plain, Mass. About 1910
Belgian Indian Growers in England and Belgium Early 1800's
Blaauw* J. Blaauw and Co., Boskoop, Holland
Bobbink and Atkins
Bobbink and Atkins, East Rutherford, N.J. About 1942
Chisholm-Merritt Julian Chisholm, Garrett Park, Maryland About 1947
Coe Frederick W. Coe, Bethesda, Maryland
Coolidge Coolidge Rare Plant Gardens, Pasadena, Calif. 1930's
Dawson Henry S. Dawson, Eastern Nurseries. Holleston, Mass. After 1923
De Wilde Roland de Wilde, Rhodo-Lake Nurseries, Bridgeton, N. J. 1947
Deerfield Deerfield Nursery, Deerfield Street P.O., N.J. 1950
Dosser* Lillie Dosscr, Centralia, Washington 1955
Exbury Evergreen Lionel de Rothschild, Exbury, Southampton, England About 1955
Feldyk Felix and Dijhuis, Boskoop, Holland 1930
Felix and Dijhuis Felix and Dijhuis, Boskoop, Holland 1946
Ferndown* D. Stewart and Son, Ltd., Ferndown, Dorset, England 1946
Gable Joseph B. Gable, Stewartstown, Pa. 1927
Ghent Growers around Ghent, Belgium Early 1830's
Girard Peter E. Girard, Girard Bros. Nursery, Geneva, Ohio 1954
Glenn Dale United States Department of Agriculture 1941
Hage* W. C. Hage and Co., Boskoop, Holland 1938
Henny Rudolph Henny, Brooks, Oregon Not Introduced
Hirado Unknown. Island of Hirado, Japan 1952
P. M. Koster, Boskoop, Holland 1920's
Kingsville* Henry J. Hohman, Kingsville Nurseries, Kingsville, Maryland
Knaphill Anthony Waterer, Woking, Surrey, England About 1870
Knaphill Strain Knap Hill Nursery, Woking, Surrey, England 1860's
Slocock Strain Goldsworth Old Nursery, Ltd., Woking 1947
Ilam Strain Edgar Stead, Ilam Estate, Christchurch, New Zealand
Exbury Strain Lionel de Rothschild, Exbury, Southampton, England Early 1930's
Koppeschaar* W. F. Koppeschaar, Boskoop, Holland
Kurumanthum K. Wada, Kakoneya Nurseries, Numazushi, Japan Before 1941
Kurume Mitozo Sakamoto, Kurume, Japan Early 1800's
Lackamas Ben Lancaster, Lackamas Gardens, Camas, Washington 1951
Macrindicum K. Wada, Kakoneya Nurseries, Numazushi, Japan Before 1941
Mayo R. P. Mayo Nurseries, Augusta Georgia About 1940
Mollis Louis Van Houtte, Ghent, Belgium Before 1873
Mortier P. Mortier, Ghent, Belgium About 1830
Occidentale Growers in England and Holland About 1895
Ornatum J. R. Gowen, Highclere, England About 1831
Ouden H. den Ouden and Son, Boskoop, Holland 1938
Pericat Alphone Pericat, Collingdale, Pa. 1931
Petry Mrs. Frank Petry, Prichard, Alabama After 1948
Pride Orlando S. Pride, Butler, Pennsylvania After 1934
Puyallup Valley Leonard F. Frisbie, Puyallup, Washington About 1954
Rustica Fiore Pleno
Charles Vuylsteke, Belgium About 1900
Rutherford Bobbink & Atkins. East Rutherford, N.J. 1920's
Sander Charles Sander, Brookline, Mass. About 1885
Satsuki Unknown, Japan Before 1700
Sawada K. Sawada, Overlook Nurseries, Mobile, Ala. About 1950
Scabrume K. Wada, Kakoneya Nurseries, Numazushi, Japan Before 1941
Shammarello A. Shammarello, South Euclid, Ohio Not Introduced
Sherwood Sherwood Nursery Co., Corbett, Oregon 1935
Southern Indian Magnolia Gardens, Charleston, S. Carolina 1840
Ten Oaks Ten Oaks Nursery, Clarksville, Maryland 1948
Viscosepalum Growers in England Early 1800's
Vuyk Vuyk van Nes Nursery, Boskoop, Holland 1926
Wadai K. Wada, Kakoneya Nurseries, Numazushi, Japan Before 1941
Westfall Quincy R. Westfall, California About 1950
Yerkes-Pryor Guy E. Yerkes, U. S. D. A., Beltsville. Maryland
*Parentage unknown.

Table II
Rhododendron Species Used In The Production Of Hybrid Azaleas
Species Native Habitat Introduced Color
R. arborescens (Pursh) Torr. Eastern U. S. Before 1814 White or pinkish
R. atlanticum (Ashe) Rehd. Eastern U. S. About 1916 White or pinkish
R. bakeri Lemm. & McKay Southeastern U. S. 1938 Deep yellow to orange scarlet
R. calendulaceum (Michx.) Torr. Eastern U. S. Before 1800 Yellow to scarlet
R. canescens (Michx.) Sweet Southern U. S. 1750? Pink and white
R. indicum (L.) Sweet Japan Before 1680 Bright red to scarlet
R. japonicum (Gray) Suringar Japan 1861 Orange-red or salmon-red to brick-red
R. kaempferi Planch. Japan 1892 Red or orange-red to pink
R. kiusianum Mak. Japan 1955 Purple
R. luteum Sweet Asia Minor, Eastern Europe 1792 Yellow
R. macropetalum Maxim. Japan 1863 Rose-lilac to rose-purple
R. molle (B1.) G. Don China 1823 Golden-yellow
R. mucronatum G. Don Japan 1819 White
R. nudiflorum (L.) Torr. Eastern U. S. About 1930 Light pink or white
R. obtusum (Lindl.) Planch. Japan About 1844 Orange-red to bright red
R. occidentale Gray Western U. S. 1850 White or pinkish
R. oldhamii Maxim. Formosa 1878 Red
R. phoenicum G. Don Unknown, may be hybrid 1824 Rose-purple to magenta
R. poukhanense Levl. Korea 1905 Pale lilac-purple
R. ripense Mak. Japan ? Rose-purple
R. roseum (Loisel.) Rehd. Eastern U. S. About 1790 Bright pink
R. scabrum G. Don Japan Before 1911 Rose-red to scarlet
R. schlippenbachii Maxim. Eastern Asia 1893 Pale to rosy pink
R. simsii Planch. China, Formosa 1808 Rose-red to bright or dark red
R. speciosum Sweet Georgia, U.S.A. 1830 Scarlet-red
R. tschonoskii Maxim. Japan, Korea 1878 White
R. viscosum (L.) Torr. Eastern U. S. Before 1731 White or suffused pink

Fig. 6


1. Arends, Georg, Mein Leben als Gartner and Zuchter, Stuttgart: Eugen Ulmer, 1951.

2. Bowers, Clement Gray, Rhododendrons and Azaleas, New York: Macmillan, 1936.

3. Hume, H. Harold, Azaleas, New York: Macmillan, 1956.

4. Lee, Frederic P., The Azalea Book, Princeton: D. Van Nostrand, 1958.

5. Pinckney, G. H., Hardy Hybrid Azaleas-Their Evolution and Range, Royal Horticultural Society, The Rhododendron and Camellia Year Book, 9:31-36, 1955.

6. Rehder, Alfred, Manual of Cultivated Trees and Shrubs, Second edition, New York: Macmillan, 1940.

7. Wilson, E. H. and Rehder, Alfred, A Monograph of Azaleas, Cambridge, Harvard Univ. Press, 1921.

8. Wyman, Donald, Shrubs and Vines for American Gardens, New York: Macmillan, 1949.