JARS v50n3 - Re-establishing the Glenn Dale Hybrids

Re-establishing the Glenn Dale Hybrids
Richard T. West
Columbia, Maryland

The overall goal of the activities reported in this article is to re-establish correct, complete collections of all of the 454 Glenn Dale azaleas at the U.S. National Arboretum in Washington, D.C., and at other arboreta and public gardens in the United States. The intent is to create accessible Glenn Dale azalea reference resources at various locations and a body of valid information about the hybrids, and to improve their commercial availability. The Glenn Dale azaleas were developed under the direction of Benjamin Y. Morrison during the 1930s to be winter-hardy at Washington, D.C., and to have large flowers; they have a bloom time from mid-April to mid-June in Washington. Today, few of the Glenn Dales are readily available to the general public from nurseries. Many varieties are propagated and sold by azalea enthusiasts, but there are still many that are impossible to find. There are no complete collections of the Glenn Dales anywhere, and there are too many errors in existing collections and in information about the hybrids. Over the past six years, and especially in the past three years, members of the American Rhododendron Society (ARS) and the Azalea Society of America (ASA) have worked together on re-establishing the Glenn Dale azaleas. Activities include locating and verifying original Glenn Dale azaleas, historical research, and the provision of cuttings and plants to a selected group of receivers who are cooperating in re-establishing collections (see Table 1).

Table 1. Ten Oaks Glenn Dale Project Cooperators
Jan Bowman Orinda, CA (Oakland, Calif. Horticultural Gardens)

Hugh A. Caldwell Middleburg, FL (Bellingrath Gardens)

Perry L. Corkern A & P Nursery, Franklinton, LA (New Orleans Botanical Garden)

Freida Hill Hill's Nursery and Greenhouse Pavo, GA (Thomasville Garden Center)

L. Courtland Lee Boxlee Glenn Dale, MD (Watkins Regional Park)

Jay W. Murray Princeton Chapter ARS Colts Neck, NJ (Jenkins Arboretum)

Ronnie D. Palmer Azalea Hill Gardens and Nursery Pine Bluff, AR (Twentieth Century Gardens)

Frank Pelurie The Nursery at Dutch Ridge Glendenin, WV (WV Botanical Garden at Coonskin Park)

Ben C. Reid Reid's Azalea Farm Stockbridge, GA (Vines Botanical Garden)

Pete Sheuchenko Lazy S's Farm Barboursville, VA (Montpelliar Estate Gardens)

J. Keith Suddreth Lenoir, NC (Broyhill Walking Park)

The Glenn Dale azaleas were created at the U.S. Department of Agriculture's old Plant Introduction Station (also called Plant Introduction Garden) at Glenn Dale, Md., about 16 miles northeast of Washington, D.C., under the direction of Morrison, who was Principal Horticulturist in the Division of Plant Exploration and Introduction and later the first Director of the U.S. National Arboretum (USNA). He gathered together at Glenn Dale hundreds of different kinds of azaleas for the program, and utilized both greenhouses and an outdoor planting in the azalea test area or "azalea woods" for hybridizing, growing, selection, and propagation for distribution. Records were kept for all of the activities. Some of the material for breeding - the Glenn Dale azalea parents - has important historical interest as it came directly from agricultural explorers such as F.A. McClure and R.K. Beattie.

The official record of the Glenn Dale azalea program is U.S.D.A. Monograph 20, The Glenn Dale Azaleas , written by Morrison and published in 1953 (1). This document contains a history of the program and descriptions of all 454 hybrids. The hybridizing work took place in the 1930s and 1940s, and the resulting hybrids were distributed to selected arboreta and nurseries in the U.S. in 1942 and from 1948 through 1952 (work was temporarily halted during World War II). Some of the receivers were the USNA and the Ten Oaks Nursery of Clarksville, Md. During the 1950s, Ten Oaks produced annual catalogs of azaleas for sale, and in one year there were almost 350 of the Glenn Dales available. They sold and shipped hundreds of thousands of azaleas in the U.S.(2).

Not all receivers of the Glenn Dales did as Ten Oaks. David Leach stated in the Introduction to Hybrids and Hybridizers , "The trade found the legions of Glenn Dales so bewildering that they were generally shunned by nurserymen. Only two large growers propagated them in any assortment representative of their splendid multiformity" (3). Morrison, himself, confessed that the nursery trade did not like his introduction of so many azaleas (4). In short time, interest waned and Glenn Dale offerings rapidly dwindled. It may be that many of the hybrids released later in the distribution program were never propagated to any extent and, consequently, were never really made available to collectors.

Azalea 'Vittata Fortunei'
Azalea 'Vittata Fortunei' overhanging
the Morrison Garden at the
U.S. National Arboretum.
Photo by Keith Woller
Mt. Hamilton hillside 
of Glenn Dale azaleas, U.S. National Arboretum
Mt. Hamilton hillside of Glenn Dale azaleas, U.S. National Arboretum.
Photo by Keith Woller

Despite Morrison's desire and efforts, there was never a complete collection at the Arboretum. Some Glenn Dales were apparently never delivered to the USNA, and many original plants received were lost soon after arrival because of drainage and other problems in early gardens. Many individuals at the USNA since Morrison have sought unsuccessfully to develop a complete collection, notably Dr. Roy Magruder, a USNA Collaborator, in the 1960s. A few individuals have developed extensive, but not complete, private collections: some of these collections are the azalea arboretum of the Ten Oaks Nursery (described later), the Brookside Gardens and the McCrillis Gardens of the Maryland-National Capital Park and Planning Commission, and the Perkins Azalea Garden of the Landon School in Bethesda, Md. In most of these collections, plant identification is incomplete for original azaleas, and the evidence is that later additions may have been incorrectly identified.

As described in the following paragraphs, current efforts to re-establish the Glenn Dale azaleas have involved, as principal participants, William C. Miller III of ARS and ASA; Barbara L. Bullock, Curator of Azalea and Rhododendron at the USNA; Andy N. Adams, Jr., retired president of the Ten Oaks Nursery; and the author, who is a member of ASA. The work has involved activities at the USNA; at the residence of Andy Adams, Jr., near the Ten Oaks Nursery; and at the Glenn Dale Station.

Activities at the U.S. National Arboretum
Beginning in the summer of 1991, Miller and West joined with Bullock shortly after her arrival at the USNA to survey Arboretum records and plantings for the Glenn Dales. Accession records, old files and papers, and planting maps were consulted, and the Glenn Dale azaleas in the various beds and groupings were examined. Interest soon focused on the large massed planting of Glenn Dale hybrids on the south slope of Mt. Hamilton. Contrary to the popular belief that the planting was composed of Glenn Dale hybrid rejects, it was found to be an organized collection of the best hybrids, including many that were named Glenn Dales, that resulted from Morrison's program. At the beginning of World War II in 1942, Morrison had arranged for a donation from Glenn Dale to the USDA of some 15,000 selected Glenn Dale hybrids, and these became the massed planting on Mt. Hamilton. It was also learned that the plants were originally tagged for identification (5).

The USNA was one of the recipients in the Glenn Dale distribution, and even though many hybrids have been lost, as previously noted, some yet unknown number of original Glenn Dales still live at the USNA. Bullock is watching for original plants and verifying the correctness of the collection (6). She has also directed a clean-up of the massed planting on the south slope of Mt. Hamilton, and has made notable progress in improving overall conditions which were a matter of great concern (7). In the clean-up, some identification tags have been found for both named and unnamed Glenn Dales. It is hoped that rare Glenn Dales might be located in the massed planting.

Glenn Dale azalea Geisha'
Glenn Dale azalea Geisha'
Photo by Richard T. West

Activities at the Ten Oaks Nursery
Andrew N. Adams, Sr., and his Ten Oaks Nursery was one of the receivers in the Glenn Dale azalea distribution program (8). A condition of the distribution was that recipients should provide annual reports to the U.S.D.A. on the status of each cultivar and the propagation experience. Morrison suggested that one specimen of each Glenn Dale be set aside and allowed to grow to full maturity. Adams responded to this obligation by creating an azalea arboretum to serve as a test garden where natural growth could occur and be monitored. He planted not only the Glenn Dales, but also azaleas of every kind he could get. The arboretum originally contained about 1,000 azaleas representing some 600 or more different cultivars. The Glenn Dales are in six sections and were all tagged for identification. The arboretum, constructed and planted in 1950 and 1951 in an isolated area of the Adams' Ten Oaks property, has never been open to the public, and the azaleas have been left undisturbed to grow on their own.

For their azalea business, Adams also designed a display garden near the main nursery buildings where their customers could see and inspect larger-sized versions of the azaleas offered for sale. Also planted in 1950-51, the garden contained some 100 selected Glenn Dales and other azaleas that showed high qualities and were popular with customers. These were also tagged for identification.

In the early 1960s, Ten Oaks ceased retail sales and became a wholesale nursery and contract landscape business. New company buildings were constructed at other places on the property, and the azalea collections became part of the Adams' residential property. Despite the intrusion on their privacy, the Adams family members have been highly supportive of the re-establishment activities, and Andy Adams, Jr., the son of original owner, has been especially involved.

The azalea plantings are being surveyed to find tags, validate plant identification at bloom time, re-tag plants and construct planting diagrams. The work is about 70 percent completed (9). Some inspection and study of the rarer azaleas have taken place. The finding of certain hybrids has been the cause of a few articles on individual Glenn Dale cultivars (10, 11). The original plants of Ten Oaks provide a "pure" source of material to re-establish collections of the Glenn Dales.

Ten Oaks Azalea Arboretum
Ten Oaks Azalea Arboretum
Photo by Richard T. West

The Ten Oaks Glenn Dale Project
In addition to the propagation of original Glenn Dales for the USNA from the Ten Oaks azalea arboretum begun in 1990, West and Miller, with the approval and support of Andy Adams, Jr., initiated "The Ten Oaks Glenn Dale Project" in 1993 to distribute Glenn Dale cuttings to volunteer propagators for regional public gardens and arboreta around the United States (12, 13). The purpose of the project is to establish regional reference collections of the Glenn Dales in addition to that at the USNA, and to improve commercial availability of the hybrids. The 11 cooperators selected to participate in the program have agreed to propagate at least one cutting for a reputable garden or arboretum. In 1993, 1994 and 1995 some 10,000 cuttings for 148 Glenn Dales were distributed. One cooperator is the Princeton Chapter of the ARS. All 11 cooperators along with their designated gardens are listed in Table 1. It is hoped that 200 to 250 original Glenn Dales can be found at Ten Oaks.

R. 'Portent' at Ten Oaks R. 'Lullaby' at Ten Oaks
'Portent' at Ten Oaks
Photo by Richard T. West
'Lullaby' at Ten Oaks
Photo by Richard T. West

Activities at the U.S.D.A. Glenn Dale Station
The old Glenn Dale Plant Introduction Station is now part of the U.S.D.A. National Germplasm Resource Laboratory. Because it is still a closed federal facility, the azalea woods (the azalea test area) of some five acres has been protected. A permit for access to the facility and the woods was obtained by the ASA in 1982 for preservation and azalea research activities. Activities through the 1980s and early 1990s were mostly basic maintenance of the paths into the woods area, and some examination and rescue of individual azaleas. An exception was the research of ASA member Ed Rothe, who became interested in a planting of Ghent azaleas in the woods, and undertook a restoration and identification of the collection (14). Co-incidental with the azalea woods activity, Miller began a thorough search for records and other materials of the Glenn Dale hybridizing program still existing at Glenn Dale, and at the Department of Agriculture and the National Agricultural Library. He found and saved many items, and, although not large in number, they have proven invaluable in the work reported here. His historical efforts have resulted in a series of articles about the Glenn Dale azaleas (15, 16, 17, 18). The records found have enabled the development of a Glenn Dale azalea database that relates hybrid name, Plant Introduction (PI) number, Bell number (the identifier used at Glenn Dale before PI assignment), and the seed lot and parentage. The database has been published as a companion to Monograph 20 entitled, The Bell Book , and was reviewed in the ARS Journal (19). The records and the database have been used to correct errors in Monograph 20 (20).

Until recently, it was generally believed that the azaleas still existing in the woods at Glenn Dale could not be identified as no identification tags had been found, there was nothing to delineate the planting or bed arrangements, and there were no records to indicate the current contents. The woods appeared to be just a mass of azaleas that were the relic of the Glenn Dale azalea program. Discoveries in 1993 of a few named Glenn Dales in a particular location that was given in an old record suggested that historical records could be directly related to the existing azaleas, and a current map of plantings could be developed from a reconstruction of original plantings.

The azalea woods at the 
Glenn Dale Plant Introduction Station
The azalea woods at the Glenn Dale Plant Introduction Station.
Photo by William C. Miller III

Utilizing a crude, 1930s hand-drawn diagram of the various plantings in the azalea woods discovered by Miller in an old file box and a later professionally drawn map of the Glenn Dale Station, a tentative map of the individual planting areas or plots was reconstructed. Inventories of azaleas planted in the plots in 1937 and 1939, plus various other inventory and planting lists of the 1930s and 1940s, were used to develop tentative contents lists. Surveys were conducted in 1994 to test whether the map and inventories for the plots were current and usable. Based on a random sampling of azaleas in the inventories, it was found that Plots 1 and 3, both locations of Glenn Dale parent plants "in permanent location," still contained most of the listed plants, although some azalea loss was found. Visual inspection of other plots suggested the likelihood that they, too, retained much of the original planting, and only Plot 20, and perhaps Plot 16, which contained the majority of selected Glenn Dale hybrids, were found to be empty of original azaleas and/or replanted with later azalea projects. From these analyses and surveys, the working hypothesis is that the great majority of Glenn Dale parent azaleas can be located, as can be some significant number of Glenn Dale hybrids. The availability of recently found acquisition records may enable complete histories for each parent azalea. Thus, the azalea woods area represents a unique and highly valuable collection; it holds the results of plant germplasm collecting over 75 years as well as some amount of the hybridization work conducted at Glenn Dale.

A few original Glenn Dale hybrids have been located already at the Station: these are 'Alexandria', 'Demure', 'Fanfare', 'Grenadier' and 'Nerissa'. Miller has found handwritten maps showing the location of some 30 named Glenn Dales in the Plot 20 area. Additionally, another drawing identifies Glenn Dales near the office complex. Many of these hybrids have not been found at Ten Oaks. It may be also that other named Glenn Dales still remain to be found in other plots.

Efforts to re-establish complete or near-complete collections of the Glenn Dale azaleas are successfully underway and will continue. Perhaps as many as 200 to 250 Glenn Dales can be found at the Ten Oaks arboretum, and an additional 50 or more may be found at the Glenn Dale Station and at the USNA. It has been especially fortunate to have found some very rare cultivars, such as 'Luna', which gives some promise for having nearer-complete collections. The search has begun for original Glenn Dale azaleas in other locations, and any information about where some may be found would be very welcomed. Only time will tell if complete collections of all the 454 hybrids can be established in fact, or whether some cultivars are lost forever.

Similarly, a computer database of correct information about each hybrid has been compiled and published. As further corrections are discovered, they are entered into the database. The database and other historical material may be deposited at the USNA. The goal of having plants and data at the Arboretum, at the least, as a primary source of reference and information is feasible.

Although those of us involved in re-establishing the Glenn Dales never thought it would be a quick or easy task, the effort required has proven to be quite time-consuming and has not allowed for the pursuit of other opportunities that have arisen. Having the opportunity to see large numbers of mature Glenn Dales, besides confirming the excellence of the hybrid group, has highlighted a variety of interesting research questions; for example, why do "sport" flowers occur and what rules are there about sporting. The exciting discovery of the ability to identify the extensive collection of historical azaleas - the Glenn Dale azalea parents - in the Glenn Dale woods has caused interest in research and propagation. At the Ten Oaks arboretum, there were originally complete collections of the Gable, Chisolm-Merritt, and U.S.D.A. Beltsville azaleas in addition to the Glenn Dales. Certainly, each of these other hybrid groups is deserving of the same attention as is being given the Glenn Dale azaleas. Hopefully, some or all of these activities can be addressed eventually, and the method of re-establishing the Glenn Dales might serve as a model for making other hybrids available.

1.  Morrison, B.Y. The Glenn Dale Azaleas. U.S. Department of Agriculture Monograph 20, Washington, D.C.; October 1953.

2.  West, R.T. Distribution of the Glenn Dale Azaleas and the Ten Oaks Nursery. The Azalean 11(4): 72; December 1989.

3.  Livingston, P.A. and West, F.H. (eds.) Hybrids and hybridizers; rhododendrons and azaleas for Eastern North America. Introduction by D.G. Leach. Newtown Square, PA: Harrowood Books; 1978, xiv.

4.  Morrison, B.Y. [Letter to Corinne Murrah] (notes taken by Roy Magruder, typed by William Miller in 1991) that, "My name is held in low regard by the nursery trade as having introduced too many Glenn Dales." 1962.

5.  West, R.T., Miller III, W.C., and Bullock, B.L. The massed Glenn Dale azaleas on Mt. Hamilton: a valuable collection at the National Arboretum. The Azalean 14(1): 8-13; March 1992.

6.  Priest, M. and Bullock, B. Verification study of the Glenn Dale azalea collection at the U.S. National Arboretum - 1993. The Azalean 16(1): 24-29; March 1994.

7.  Miller III, W.C. and West, R.T. The massed Glenn Dale azaleas on Mt. Hamilton at the National Arboretum: a commentary and a call for action. The Azalean 14 (2): 42-43; June 1992.

8.  West, R.T. Distribution of the Glenn Dale azaleas and the Ten Oaks Nursery. The Azalean 11(4): 69-73; December 1989.

9.  West, R.T. The azaleas of Ten Oaks Nursery: a preliminary report. The Azalean 14(3): 65-69; September 1992.

10.  West, R.T. and Miller III, W.C. Correction of the official description of 'Furbelow'. The Azalean 13(4): 74-75; December 1991.

11.  (West, R.T. and Miller III, W.C.) Cover photograph and text for 'Scherzo'. The Azalean 14(1): 4.; March 1992.

12.  West, R.T. and Miller III, W.C. Ten Oaks Glenn Dale project. The Azalean 15(1): 16; March 1993.

13.  West, R.T. and Miller III, W.C. The Ten Oaks Glenn Dale project begins. The Azalean 15(3): 56-57; September 1993.

14.  Rothe, E. The Glenn Dale collection of Ghent azaleas, Part 1. The Azalean 11(1): 6-7; March 1989.

15.  Miller III, W.C. The evergreen azalea cultivar 'Ben Morrison'. J. Amer. Rhod. Soc. 38(4): 178-179; October 1984.

16.  Evans, C.H. and Miller III, W.C. Pattern of sporting. The Azalean 7(1): 1 -2; March 1985.

17.  Rothe, E. and Miller, W.C. The most unusual striped flower. The Azalean 10(1): 5-8; March 1988.

18.  Miller III, W.C. More on the evergreen azalea 'Ben Morrison'. J. Amer. Rhod. Soc. 42(3): 159-161; October 1988.

19.  Voss, D.H. Book review: The Bell Book. J. Amer. Rhod. Soc. 48(3): 163; Summer 1994.

20.  West, R.T. Correction of parentage for some Glenn Dale azaleas. The Azalean 15(3): 54-56; September 1993.

Richard T. West is a native of Washington, D.C., and now resides in Columbia, MD. He is a long-time member of the Azalea Society of America and has a special interest in the Glenn Dale azaleas.