JARS v46n2 - National Native Azalea Repository

National Native Azalea Repository
North Carolina Arboretum to Hold Complete Collection
Rich Owings
Asheville, North Carolina


The North Carolina Arboretum is home to the National Native Azalea Repository, a germplasm collection focusing on the 17 species of azaleas native to the United States. Eleven of these species are found within 100 miles of the Arboretum's location in Asheville, N.C.

The North Carolina Arboretum of the University of North Carolina is a newly created public garden in Asheville, N.C. It is located adjacent to the Blue Ridge Parkway on 424 acres of the Bent Creek Experimental Forest in the Pisgah National Forest. The Arboretum's missions include education, display, conservation, research and economic development, both in terms of tourism and the emerging green industries in North Carolina. A $1.8 million Horticultural Support Facility is to be dedicated in the spring of 1992 which will include a 7,200 square-foot glass greenhouse with a computerized environmental control system, fog propagation and HID lights. The head house includes walk-in coolers, classroom and laboratory space. These facilities will provide an ideal environment for the propagation of deciduous azaleas, as well as space for research on this complex group of plants.

In 1988, Dr. John Creech and Mr. David Dean visited the North Carolina Arboretum with the suggestion of creating such a repository. Dr. Creech, a renowned plant explorer and retired director of the National Arboretum in Washington, D.C., is currently a member of the Arboretum's board of directors. Dr. Creech served as the interim director of the North Carolina Arboretum until George Briggs was hired as director in 1987. David Dean was an active member of the American Rhododendron Society and an avid grower and collector of the genus prior to his death in 1991.

The Collection

The National Native Azalea Repository is intended to be the most complete collection assembled of azalea germplasm for those species native to the United States. It is our hope that this collection will be of maximum interest to our many user groups: azalea enthusiasts, botanists, researchers, nurserymen and plant breeders, as well as the general public. The varieties that create the best floral display will be displayed in the core garden areas where up to a million visitors a year are expected to see them.

Systematic collection activities have commenced centering on the genetic variation found within native azaleas. Examples of each species and more than 60 botanical and cultivated varieties are being grown in the Arboretum's nursery and will be moved this spring to the site within the Scientific and Botanical Plant Collections Area alongside Bent Creek. The site includes native stands of Rhododendron arborescens and R. calendulaceum and encompasses various habitats including rocky slopes, rich bottomland, wet drainage channels and riparian sites.

R. calendulaceum in the wild at the
R. calendulaceum in the wild at the Arboretum.
Photo by Rich Owings

Various levels of taxa will be featured in the repository. Species material will include individuals with different morphological characteristics, botanical varieties, representatives of the various habitats and segments of each of the 17 species ranges. Within each species, cultivated varieties will also be included. There are over 140 known cultivars and selections in this group, including 36 clones of the flame azalea ( Rhododendron calendulaceum ).

Hybrids between the various native species will also be displayed. A search of existing literature has revealed over 50 named varieties of interspecific hybrids. Rhododendron arborescens and R. bakeri figure most prominently in these crosses.

Naturally occurring hybrid populations will also be featured, such as the famous hybrid swarm on Gregory Bald in the Great Smoky Mountains National Park, where Rhododendron arborescens , R. bakeri and R. viscosum have interbred to form a hybrid complex which is one of the most unique naturally occurring floral displays in the United States. Working through a collection permit with the Great Smoky Mountains National Park, staff members of the North Carolina Arboretum conducted an expedition this spring to document representative and superior individuals to Gregory Bald. The staff will return this fall for seed collections and again next summer to obtain cuttings for asexual propagation of selected clonal material. Through these efforts an ex situ collection of these plants will be established at the Arboretum.

Rhododendron hybrid at Gregory Bald Rhododendron hybrid at Gregory Bald
Naturally occurring Rhododendron hybrids at Gregory Bald, Great Smoky Mountains National Park.
Photos by Arthur Joura

The final group to be included will involve hybrids between native and exotic taxa. There are nearly 50 hybrids of this nature documented in the literature. These include many of the famous Ghent, Mollis, Knap Hill, Exbury and Windsor Park azaleas. No doubt there are many more for which the parent species are unknown.

New selections and hybrids are being named and released each year. It is the intention of the North Carolina Arboretum to add new selections to the repository as they become available.

R. austrinum
R. austrinum
Photo by Ron Lance

Future Research Activities

This complex group of plants offers many opportunities for research. On a botanical level, collection activities lend themselves to the study of morphological differences at the various extremes of each species' natural range. The study of botanical varieties, herbarium development, exploration of naturally occurring hybrid swarms in addition to the stand at Gregory Bald, and the development of morphology-based, non-floral keys are additional possibilities. Another research avenue would be to utilize isozyme analysis to determine the species parentage of undocumented hybrids, including the taxonomically confused group at Gregory Bald. Such a tool could also be used for the verification and documentation of our collection. Another use for this technology would be to conduct genetic studies on the relationships between native and Asian species. Through the use of Arboretum facilities, such as the planned laboratory complex at the Horticultural Support Facilities, the North Carolina Arboretum would like to support and encourage such research, whether initiated by our staff or visiting researchers.

R. prunifolium
R. prunifolium at Callaway Gardens, Pine Mountain, Ga.
Photo by Ron Lance

Plant Development Programs

The North Carolina Arboretum is currently initiating a Plant Development Program which will include selection, introduction and distribution components. Possible avenues of development for the native azalea group include the evaluation of currently available cultivars for superior performance and the selection of outstanding clones from the Gregory Bald site. Because of the large numbers of hybrid azaleas currently available and the number of active azalea breeders working with native species, it is doubtful that an actual azalea breeding program will be established as part of our plant development efforts. This does not preclude selection work utilizing existing clones to search for such desirable characteristics as summer bloom time and fragrance.

Rich Owings is a horticulturist at the North Carolina Arboretum, University of North Carolina.