by Charles Andrews
The first gardening book dedicated solely to rhododendrons was a small book, Rhododendrons & Azaleas (1911), by Englishman William Watson, curator of the Royal Botanic Gardens Kew. It followed another small volume published in 1871 by American Edward Sprague Rand Jr., The Rhododendron and “American Plants”: A Treatise on the Culture, Propagation, and Species of the Rhododendron. American plants included Rhododendron, Azalea, Kalmia, Gaultheria, and Vaccineum, whether or not the species came from America. Scottish naturalist John Guille Millais published the first detailed work on rhododendrons in his illustrated two-volume Rhododendrons and Their Various Hybrids (1917, 1924). In 1921, between the publishing of Millais’ two volumes, the Arnold Arboretum published the first monograph dedicated solely to azaleas, Ernest Henry Wilson and Alfred Rehder’s Monograph of Azaleas.
While various American floras from the late 1700s to modern times included mention of azaleas and rhododendrons, America’s first major work on rhododendrons was Rhododendrons and Azaleas: Their Origins, Cultivation and Development, written by Clement Gray Bowers in 1936. Bowers was followed by various books on rhododendrons, rhododendrons and azaleas, or just azaleas, including Harold H. Hume’s Azaleas (1948), the American Horticultural Society’s Azalea Handbook (1952), Frederick P. Lee’s Azalea Book (1958), and Fred C. Galle’s simply named Azaleas (1985). The only book ever written solely on azaleas native to America is L. Clarence Towe’s American Azaleas (2004).
In Great Britain, after Millais major work on rhododendrons came The Species of Rhododendron (1930), published by The Rhododendron Society (Great Britain). Frederick Street’s Azaleas (1959) was the first azalea book published in Britain. Below is an extensive annotated list of selected books and articles covering azaleas and other rhododendrons, with an emphasis on native azaleas. Additional references may be found on this web site under Useful Links.
Bartram, William. (1791). Travels through North and South Carolina, Georgia, East and West Florida, the Cherokee Country, with extensive territories of the Muscogulges or Creek confederacy, and the country of the Chactaws. Philadelphia, PA: James & Johnson. 520 pp + index.
This classic work documents Bartram’s four-year exploration in the 1770s of what is now the southeastern United States. Written with wonderful imagery by a naturalist and philosopher, Travels is a delight to read. Bartram was the first to describe the colorful flame azalea, now known as the species R. calendulaceum. To learn about the azaleas Bartram saw and documented, read our article, "William Bartram's Azaleas."
Berrisford, Judith. (1964). Rhododendrons and azaleas. London: Farber and Farber. 268 pp + index.
While it covers most of the important evergreen Rhododendron species, This British gardening book is not useful for learning about American azaleas. Some deciduous azalea species are barely discussed (240-244), with additional pages listing some European hybrids (e.g., Mollis, Ghent, Knap Hill, etc.). R. alabamense, austrinum, bakeri, and speciosum are not mentioned. R. nudiflorum and roseum are simply stated to be similar to canescens.
Bowers, Clement Gray. (1936, rev 1960). Rhododendrons and azaleas: Their origins, cultivation and development. New York, NY: MacMillan Company. 522 pp + index (1936). 494 pp + index (1960).
A good and thorough, if outdated, coverage of rhododendrons and azaleas, all the more impressive since Bowers had few models to follow for such a book. Contains an early exposition of native azaleas from a rhododendron expert, but one who had a strong bias toward the northeastern United States, where cold-hardy plants are a necessity.
Bowers, Clement Gray. (1954). Winter-hardy azaleas and rhododendrons. Boston: Massachusetts Horticultural Society. 108 pp + index.
Primary interest is in growing rhododendrons and azaleas in the northeastern U.S. Briefly discusses deciduous azaleas (p. 64-69).
Braun, E. Lucy. (1941). The red azaleas of the Cumberlands. Rhodora, 43: 31-35.
Braun describes the “red azalea” of the Cumberland Plateau and Cumberland Mountains of eastern Kentucky as a new species, R. cumberlandense. Braun had observed this plant since 1931 and thought it different enough from R. calendulaceum and R. bakeri to be declared a new species. Gives a clear description of its characteristics and compares it with R. calendulaceum.
Breakey, E. P. (1960, July). Notes on our western azalea rhododendron occidentale. Bulletin American Rhododendron Society, 14 (3). Available online at Virginia Tech Digital Library and Archives.
Contains one of the best descriptions of western azalea distribution and habitat.
Brooklyn Botanical Garden. (1971). Handbook on rhododendrons and their relatives. Revised printing of Plants and Gardens 27 (2). 96 pp.
Articles on plants of the Heath family. Includes “Rhododendrons–a genus of surprises” by David Leach, “America’s native azaleas” by Henry Skinner, and “Favorite rhododendrons and azaleas by region.”
Bruce, Harold. (1976). Wild azaleas (chapter 5, pp. 97-114). How to grow wild flowers and wild shrubs and trees in your own garden. New York, NY: Alfred A. Knopf.
Winterthur was the estate and gardens of Henry F. Du Pont in Delaware. Hal Bruce was Winterthur’s plant curator, beginning in the 1960s. The entire chapter discusses native azaleas, which is an excellent discussion of the eastern natives.
Bruce, Harold. (1976, October). Deciduous azaleas at Winterthur. Bulletin American Rhododendron Society, 30 (4). Available online at Virginia Tech Digital Library and Archives.
Identifies native, Old World, and hybrid azaleas growing at Winterthur Gardens in Delaware.
Cantrell, H. Furman. (1979, April). Native azaleas: Gregory Bald. Bulletin American Rhododendron Society, 33 (2). Available online at Virginia Tech Digital Library and Archives.
Describes native azaleas on Gregory Bald, perhaps the best known location for observing natural hybridization.
Cantrell, H. Furman. (1980, October). Native azaleas: Wayah Bald. Bulletin American Rhododendron Society, 34 (4). Available online at Virginia Tech Digital Library and Archives.
Describes native azaleas on Wayah Bald, primarily the flame azalea and sweet azalea.
Clarke, J. Harold. (1956, July). A selected list of rhododendron literature. Bulletin American Rhododendron Society, 10 (3): 163-168. Available online at Virginia Tech Digital Library and Archives.
Contains over 100 references to rhododendrons published prior to 1956.
Clarke, J. Harold. (1960). Getting started with rhododendrons and azaleas. Garden City NY: Doubleday and Company. 260 pp + index.
Primarily a book on rhododendrons and azalea culture. Brief discussion on species and varieties.
Cox, Peter A. (1985). The smaller rhododendrons. Portland , OR: Timber Press. 261 pp + index.
This book, a complete rewrite of his earlier 1973 book, Dwarf Rhododendrons, covers those rhododendrons typically under five feet. Included are most evergreen azalea species and a short list of hybrids. The only member of Pentanthera subgenus in this book is R. canadense. R. atlanticum, which arguably qualifies as a smaller rhododendron, is not covered here but is in his later book on the larger rhododendrons. Written primarily for the British audience.
Cox, Peter A. (1990, orig 1979). The larger rhododendron species. Portland , OR: Timber Press. 377 pp + index (1990).
Companion volume to Scottish rhododendron expert Peter Cox’s 1985 Smaller Rhododendrons. This book on the larger rhododendrons includes most American azalea species, using the classification revisions of the Edinburgh Royal Botanic Garden proposed by David F. Chamberlain and James Cullen, placing them under Pentanthera subgenus. Species descriptions (108-123) range in length from two pages for occidentale to a third of a page, with most less than a page. Chapter 1 includes a history of rhododendron distribution and evolution. Written primarily for the British audience.
Cullen, James. (2005). Hardy rhododendron species: a guide to identification. Portland , OR: Timber Press. 483 pp + index.
Recent book by British rhododendron classification expert Cullen includes keys and brief descriptions for subgenus Pentanthera (226-246), where all American azaleas have been placed. The introduction includes a discussion on rhododendron structure, which helps one understand the how rhododendron species are both similar and differ among themselves. Serrulatum and oblongifolium are rolled up into R. viscosum. R. flammeum is not mentioned, nor given as a synonym. R. prinophyllum may only be found in a brief mention at the end of section Pentanthera, but not included in the key.
Davidian, H. H. (1982, 1989, 1992, 1995). The rhododendron species. Four volumes. Portland , OR: Timber Press. 421 pp + index (vol 1). 338 pp + index (vol 2). 374 pp + index (vol 3). 178 pp + index (vol 4).
Compiled by a leading taxonomist on the genus, volume 1 is lepidotes; volume 2 is elepidotes, part 1; volume 3 is elepidotes, part 2; and volume 4 is azaleas. Davidian was associated with the Royal Botanical Garden, Edinburgh, for over 40 years. His work is based primarily on morphological characteristics and did not consider recent studies on chemical and micro characteristics like DNA. Text composed of keys to the species followed by species descriptions. Davidian’s descriptions of deciduous azalea species are some of the best available.
Darden, Jim. (1985). Great American azaleas: A guide to the finest azalea varieties. Clinton, NC: The Greenhouse Press. 95 pp + index.
A highly useful pictorial discussion of evergreen azaleas according to color, flower forms, bloom times, types, and hybridizers. Each category, e.g., late blooms, includes the author's recommendations of the best in this category. Concludes with a table of characteristics for the author's choice of the top 300 azalea varieties. Limited only by the fact that post-1985 varieties are not included.
Ewan, Joseph. (1979, October). History of exploring for rhododendrons in Southeastern United States. Bulletin American Rhododendron Society, 33 (4). Available online at Virginia Tech Digital Library and Archives.
Interesting summary of the early plant explorers in the southeastern U.S. and the plants they found, from Rev. John Bannister and the swamp azalea to William Ashe and the coast azalea.
Fairweather, Christopher. (1979). Rhododendrons and azaleas for your garden. Antony, France: Editions Floraprint Ltd. 127 pp + index.
Glossy picture book from former manager of Exbury Gardens. From the British perspective, covers culture and outstanding plants, mainly hybrids. Includes section on camellias as well.
Galle, Fred C. (nd ). Native and some introduced azaleas for southern gardens. Ida Cason Callaway Foundation Booklet No. 2. Pine Mountain, GA: Ida Cason Callaway Foundation. 28 pp. Also published in (1967) Horticultural Magazine, 46: 2-28.
While somewhat outdated because of new species (R. eastmanii, R. colemanii) and name changes (R. nudiflorum=R. periclymenoides, R. speciosum=R. flammeum, R. roseum=R. prinophyllum) this is still a very useful booklet with good summaries of native azalea species.
Galle, Fred C. (1987). Azaleas (revised ed.). Portland, OR: Timber Press (1995 printing). 471 pp + index.
Still the most thorough treatment of azaleas today. Much of the information on deciduous azaleas is based on Lee’s Azalea Book, updated with most of the known cultivars as of the 1980s.
Henry, Mary Gibson (Mrs. Norman). (1946). Deciduous rhododendrons at Gladwyne. The Rhododendron Year Book 1946, pp. 35-41. Royal Horticultural Society.
Mrs. Henry was an amateur field botanist, plant hunter, and collector. She established the Henry Foundation for Botanical Research at Gladwyne, PA. Henry knew native azaleas well and was collecting the Oconee azalea in Georgia and the Cumberland azalea in Kentucky in the 1930s. This article tells of her searches and observations, showing that she was in the forefront of native azalea research in the 1930s and 40s.
Hill, Polly (Mrs. Julian). (1978, October). Choptank river hybrids. Bulletin American Rhododendron Society, 32 (4). Available online at Virginia Tech Digital Library and Archives.
Describes the azaleas she found on the Choptank River in Maryland in Delaware and Maryland. While Hill considered them hybrids, recent testing suggests they simply may be forms of the tetraploid R. atlanticum.
Hume, H. Harold. (1931). Azaleas and camellias (pp. 19-26). New York, NY: MacMillan Company. 86 pp + index.
Hume was a horticulturist, professor, dean of the College of Agriculture at the University of Florida, and president of Glen St. Mary Nursery near Jacksonville, FL. He specialized in citrus, camellias, and azaleas. This small volume is one of the first American books to discuss azaleas in some detail.
Hume, H. Harold. (1948). Azaleas: Kinds and culture. New York, NY: MacMillan Company. 189 pp + index.
While information pertinent to American azaleas will be found throughout the book, the first 58 pages, through chapter 4 on deciduous azaleas, provide details of what was known about American azaleas in 1948. Hume listed common names for many American azaleas in his first book but omitted them entirely in this one. Though dated and missing the latest information on azalea species, this is still one of the best discussions ever written on azaleas.
Judd, Walter S. and Kathleen. A. Kron. (1995). A revision of rhododendron VI: Subgenus pentanthera (sections sciadorhodion, rhodora and viscidula). Edinburgh Journal of Botany, 52 (1): 1-54.
Continuation of Kron (1993) on the classification of deciduous azaleas, covering R. canadense and R. vaseyi. A highly technical report.
Kessell, Mervyn S. (1981). Rhododendron and azaleas. Poole, Dorset: Blandford Press. 170 pp + index.
British book on rhododendron culture with some basic history.
Kraxberger, Meldon, ed. (1980). American rhododendron hybrids. Tigard, OR: American Rhododendron Society. 244 pp.
Extensive list with descriptions and ratings of registered American hybrids. Includes articles on hybridizing and hybridizers in various parts of the U.S., and “Good-Doers” by region. A useful but dated book.
Kron, Kathleen A. (1993). A revision of rhododendron section pentanthera. Edinburgh Journal of Botany, 50 (3): 249-365.
Based on her PhD dissertation, this reports on her study of most deciduous azaleas. In her opinion, R. canescens, R. periclymenoides, and R. prinophyllum should be considered separate species, but R. serrulatum and R. oblongifolium should be considered within the highly variable species, R. viscosum. A highly technical report using botanist terminology.
Kron, Kathleen A. (1996, December). Identifying the native azaleas [part 1]. The Azalean 18 (4): 72-78.
Describes the characteristics of the eastern native azalea species without technical language.
Kron, Kathleen A. (1997, September). Identifying the native azaleas, part 2. The Azalean 19 (3): 48-50.
Following her descriptions of native species in part 1, this part provides an identification key and a chart of distinguishing characteristics for the similar prinophyllum, periclymenoides, and canescens.
Krüssman, Gerd. (1970). Rhododendrons: Their history, geographical distribution, hybridization and culture. London: Ward Lock Ltd. 94 pp + index.
Written (in English) from a European perspective by the director of the Dortmund Botanischer Garten Rombergpark. Mostly on culture. Includes early history of rhododendron and azalea but with several factual errors and misleading statements. Has brief description of species, including North American species, and a lengthy list of named cultivars.
La Croix, I. F. (1973). Rhododendrons and azaleas. Newton Abbot, Devon (UK): David and Charles. 246 pp + index.
Another British book, but a good overview of the subject. Culture and descriptions of species take up most of the book. Includes some history, distribution, and a list of hybrids with short descriptions.
Leach, David G. (1958, January). A new look at the azaleas and rhododendrons of the Blue Ridge mountains. Bulletin American Rhododendron Society, 12 (1). Available online at Virginia Tech Digital Library and Archives .
Leach was highly impressed with rhododendrons from the southern Appalachians. He describes their ability to hybridize and the difficulty in distinguishing species. A excellent article which helps one to understand how complex and difficult to classify the group of American azaleas really are.
Leach, David G. (1959, July). Native eastern azaleas. Bulletin American Rhododendron Society, 13 (3). Available online at Virginia Tech Digital Library and Archives.
From an informative talk given at an ARS convention.
Leach, David G. (1961). Rhododendrons of the world and how to grow them. New York: Charles Scribner’s Sons. 536 pp + index.
Excellent book on rhododendrons does not cover azaleas. This omission from an undisputed azalea expert make one cry.
Lee, Frederic P. (1958, rev 1965). The azalea book. Princeton, NJ: D. Van Nostrand Company. 300 pp + index (1958). 408 pp + index (1965).
This book written for gardeners by Lee significantly updated the smaller Azalea Handbook compiled six years earlier by the American Horticultural Society.
Lee, Frederic P., Fred O. Coe, B. Y. Morrison, Milo Perkins, and Freeman Weiss, eds. (1952). The azalea handbook. Washington, DC: American Horticultural Society. 148 pp.
Excellent book for gardeners that goes beyond the information in Hume (1948).
Lemmon, W. P. (1937/1938?). Notes on a study of the southeastern azaleas with description of two new species. Bartonia, 19: 14-17.
Identifies Azalea fastigifolia and Azalea bakeri as two new species. A. fastigifolia is now considered a hybrid, and A. bakeri is now identified as the species R. cumberlandense.
Livingston, Philip A. and Franklin H. West, eds. (1978). Hybrids and hybridizers: Rhododendrons and azaleas for eastern North America. Newtown Square, PA: Harrowood Books. 252 pp + index.
The title of the book is somewhat misleading, for the bulk of the book, the first five chapters, is comprised of interesting biographical sketches of five American giants in the hybridization of rhododendrons and azaleas: Charles Owen Dexter, Joseph Benson Gable, Benjamin Yo Morrison, G. Guy Nearing, and Anthony M. Shammarello. Chapter six contains a list of the best new hybrids by climatic zone, a list of hybrid rhododendrons and azaleas registered 1959-1975, a list of hybridizers in the eastern U.S. and Canada, and short paragraphs on 45 contemporary hybridizers (e.g., Peter Girard, David Leach, Polly Hill, Ralph Pennington, Charles and Velma Haag, Robert Gartrell, etc). Chapter seven and two appendices list plant recommendations.
Marshall, William. (1785). Planting and ornamental gardening: A practical treatise (pp. 77-78). London: J. Dodsley.
Perhaps the earliest American botanical reference. Lists species Azalea nudiflora, the red-flowered azalea, and Azalea viscosa, the white sweet azalea.
Millais, John G. (1917, 1924). Rhododendrons and the various hybrids. Two volumes. London: Longmans. 263 pp + index (vol 1). 266 pp + index (vol 2).
First detailed work on rhododendrons, written from the British point of view. Millais, an author on various books on animals, decided to become an expert on rhododendrons and produced this folio-size, two-volume work on the Rhododendron genus. WWI interrupted the publishing of the second volume, which turned out to be fortunate, allowing inclusion of recent discoveries and the contributions of Wilson and Rehder. The rare volumes contain many color illustrations and photographs. Millais provided a description of practically every known species.
Millais, J. G. and P. D. Williams. (1918). American azaleas and their hybrids. Rhododendron Society Notes, 1 (3): 122-130.
This note accompanied a published letter from Professor Charles S. Sargent and lists the known American azaleas with a short description, and discusses how they have been used in hybridization. R. albiflorum is included as well as several not now considered separate species.
Mossman, Frank D. (1974, April). The western azalea, rhododendron occidentale. Bulletin American Rhododendron Society, 28 (2). Available Online at Virginia Tech Digital Library and Archives
Contains a good description of the western azalea.
Mossman, Frank D. and Brit M. Smith. (1969, July). Rhododendron occidentale–one species or many? Bulletin American Rhododendron Society, 23 (3). Available online at Virginia Tech Digital Library and Archives.
Mossman and Smith discuss the great variability found among western azalea specimens. These explorers preferred to collect samples from the unusual rather than the typical plants.
Prince, Martha. (1973, January). Exploring the color range of the native azalea R. calendulaceum. Bulletin American Rhododendron Society, 27 (1). Available online at Virginia Tech Digital Library and Archives.
Brief article written by a native of Georgia who lives on Long Island that argues most flame azaleas in cultivation in the Northeast are inferior to wild southern Appalachian natives. She describes not only the straight yellow to deep orange scarlet range, but also flowers with light orange tinged with pink and clear soft pink with white upper petal blotched with yellow.
Prince, Martha. (1981, October). Our wild eastern treasures: native azalea. Bulletin American Rhododendron Society, 35 (4). Available online at Virginia Tech Digital Library and Archives. Reprinted from American Horticulturist.
Brief descriptions with pictures of the eastern natives.
Rand, Edward Sprague Jr. (1871). The rhododendron and “American plants”: A treatise on the culture, propagation, and species of the rhododendron. Boston, MA: Little, Brown, and Company. 176 pp + index.
“American plants” was a British term for Rhododendron, Azalea, Kalmia, Gaultheria, Vaccineum, and other Ericaceae found primarily in North America. The term encompassed similar plants not indigenous to America. First American book on rhododendrons. Briefly describes deciduous azaleas A. arborescens, A. nudiflora, A. viscosa, A. glauca, A. nitida, A. calendulacea, A. pontica, A. occidentalis, and Rhodora canadensis.
Rehder, Alfred. (1921). The azaleas of North America. A monograph of azaleas: Rhododendron subgenus anthodendron, by Ernest Henry Wilson and Alfred Rehder, publication of the Arnold Arboretum, No. 9: 107-196. Cambridge, MA: The University Press. Also reprinted 1977 Sakonett, RI: Theophrastus Publishers.
Written for botanists and those educated in plants, this treatise was the most detailed analysis of North American azaleas at the time. Classification of this group of plants has now changed from the Balforean system Rehder used. Later taxonomists have adjusted some of Rehder’s species, varieties, and forms. New species have been added and some well-known names have been changed since 1921. Still, this classic work is thorough and quite valuable, even if written in a highly technical and abbreviated style, which will often appear cryptic to the layman.
Reiley, H. Edward. (1992). Success with rhododendrons and azaleas. Portland OR: Timber Press. 269 pp + index.
Perhaps the best book for those beginning to learn about rhododendron and azaleas. Begins with a good history chapter. Includes "Good-Doer" recommendations for all parts of the U.S. and other countries. Primarily a book on culture, well explained. Includes appendices on plants by color and cold-tolerant plants.
Rhododendron Species Foundation Library Committee. (1981). A select bibliography of rhododendron literature. Rhododendron Species Foundation.
Pamphlet containing about 85 references pertaining at least in part to rhododendrons. Most are listed as available in the Rhododendron Species Foundation Library.
Roane, Martha K. (1975, spring). Rhododendrons native to Virginia USA. Virginia Journal of Science, 26 (1): 6-12.
Contains identification keys, descriptions and distribution maps of rhododendrons in Virginia. Some of the species she attributes as native to Virginia have been questioned by other botanists (e.g., R. serrulatum, R. canescens).
Roane, Martha K. and Josephine DeN. Henry. (1981, summer). The species of rhododendron native to North America. Journal American Rhododendron Society, 37 (3): 137-145, 164-168. Also published in (1981) Virginia Journal of Science, 32 (2): 50-68.
Contains identification keys and descriptions of 27 North American rhododendron species. Some are no longer considered separate species.
Skinner, Henry T. (1952). Character patterns in the early flowering azaleas of the southeastern United States. PhD dissertation, University of Pennsylvania. 81 pp. Copy in Henry T. Skinner papers, special collections, Small Library, University of Virginia.
Skinner’s dissertation is based on his mammoth 1951 exploration covering 25,000 miles. While discussing his entire floral season expedition, the scope of Skinner’s thesis is limited to early flowering azaleas (calendulaceum and earlier), concentrating mainly on the pink azaleas. Little known, this is still an important work for the results of his analysis of American azalea morphological characteristics.
Skinner, Henry T. (1955, January, April). In search of native azaleas. Morris Arboretum Bulletin, 6 (1): 1-10 & 6 (2): 15-22, University of Pennsylvania.
The article, originally published in 1955, is available online from the Electronic Text Center, University of Virginia Library along with images and transcriptions of original documents from the trip conducted in 1951. Record Book #1; Record Book #2; Trip Routes.
Skinner, Henry T. (1961, May 11-14). Classification of the native American azaleas. Proceedings International Rhododendron Conference. Portland, OR, 81-86, American Rhododendron Society.
Excluding canadense, vaseyi, and occidentale, Skinner discusses his ideas pertaining to native azalea species and his thoughts on hybridization. His opinions are based on his extensive study of native azaleas in 1951.
Skinner, Henry T. (1971). America’s native azaleas. Handbook on rhododendrons and their relatives. Brooklyn Botanical Garden. Revised printing of Plants and Gardens 27 (2).
Skinner gives his evaluation of the American species.
Solymosy, Sigmond L. (1976). A treatise on native azaleas. Bulletin of the Louisiana Society of Horticultural Research, 4 (2): 7-74.
Valuable treatise, published posthumously, contains the results of the Louisiana taxonomist’s research on native azaleas. He does not cover atlanticum, canadense, calendulaceum, cumberlandense, or vaseyi. An important contribution, followed up no where else, is his study of root structures, noting the uniqueness of serrulatum. Included are pages of tables comparing characteristics attributed to species (with often disparate descriptions) by various authors.
Stevenson, John Barr, ed. (1930, rev 1947). The species of rhododendron. Edinburgh: The Rhododendron Society. 853 pp + index (1947).
This book produced exactly one page of description for each rhododendron species, with the species grouped in series of similar species begun with Sir Isaac Bayley Balfour of the Royal Botanic Garden Edinburgh. Keys are provided as aids to identify subseries and species. The effort was divided among the three major divisions of rhododendrons and assigned to three botanists. Harry F. Tagg developed the elepidote data, John Hutchinson the lepidote data, and Alfred Rehder the azalea data. Thus, azalea information here is similar to Wilson and Rehder’s 1921 Monograph, but briefer and kinder to the lay reader. The 1947 revision is composed of inserted pages for 31 additional species, one of which is the Japanese deciduous azalea R. amagianum, placed in the Schlippenbachii subseries of the Azalea series.
Street, Frederick. (1959). Azaleas. London: Cassel and Company. 270 pp + index.
First book published in Great Britain limited to the subject of azaleas. Producing more of a biography or history book than a gardening book, Street provides, in highly readable form, many details of the history of American azaleas brought to Europe. The book covers the impact of changing gardening styles on the popularity of azaleas in Great Britain.
Street, John. (1988). Rhododendrons. Chester CT: Globe Pequot Press. 142 pp + index.
Briefly mentions azaleas in the chapter, A Brief History, and describes (p 14) the Pinxterbloom (R. periclymenoides) as having “a strong attractive scent,” yet most other sources say Pinxterbloom has little or no fragrance. Contains many pictures and descriptions of both selected Rhododendron species and cultivars, none of which are deciduous azaleas.
Towe, L. Clarence. (2004). American azaleas. Portland, OR: Timber Press. 142 pp + index.
Delightful book on native azaleas, based on Towe’s many years of observation of plants in the wild. Much of the book is anecdotal in nature. We wish there were more information on each of the American species.
Watson, William. (nd ). Rhododendrons and azaleas. London: T. C. and E. C. Jack. 114 pp + index.
William Watson was curator of the Royal Botanic Gardens Kew, 1901-1922, beginning as a gardener there in 1879. This may be the first British gardening book on the topic of rhododendrons and azaleas.
Wherry, Edgar T. (1943, October). The American azaleas and their variations. The National Horticultural Magazine, 22: 158-166.
Article is based on Wherry’s study of native azalea species and hybrids, begun to answer questions posed by Mrs. Mary Gibson Henry. He provides a fairly complex set of keys to help identify these highly variable plants.
Wilson, Ernest Henry. (1921). The Azaleas of the Old World. A monograph of azaleas: Rhododendron subgenus anthodendron, by Ernest Henry Wilson and Alfred Rehder, publication of the Arnold Arboretum, No. 9: 107-196. Cambridge, MA: The University Press. Also reprinted 1977 Sakonett, RI: Theophrastus Publishers.
Good if dated exposition filled with history and technical descriptions of the evergreen and deciduous azalea species of Asia and eastern Europe. Known as Chinese Wilson, he had traveled in Asia studying and collecting plants. Wilson helped introduce Kurume azaleas to the West.
Wilson, Ernest Henry and Alfred Rehder. (1921). A monograph of azaleas: Rhododendron subgenus anthodendron, Arnold Arboretum, No. 9. Cambridge, MA: The University Press. Also reprinted 1977 Sakonett, RI: Theophrastus Publishers. 206 pp + index.
Monograph in two parts. Wilson wrote “The Azaleas of the Old World” (1-106) and Rehder wrote “The Azaleas of North America” (107-196). Rehder’s tract on the native American azaleas is often incorrectly attributed to Wilson, who is listed as first author of the overall monograph. This is the first book ever devoted to the single subject of azaleas but not an easy book for the layman. It is a highly technical work, intended primarily for botanists and horticulturists.