JARS v51n4 - Rhododendron bakeri vs. R. cumberlandense

Rhododendron bakeri vs. R. cumberlandense
Donald H. Voss
Vienna, Virginia

Considerable controversy has arisen among azalea fanciers with respect to K.A. Kron's 1993 revision citing Rhododendron cumberlandense E.L. Braun (1941) as the correct name for the Cumberland azalea. This taxon has been widely known in the past half century as R. bakeri (Lemmon & McKay) Hume. (A taxon is a group of plants comprising one category in a classification scheme; e.g., an individual species.) In 1938 Lemmon and McKay applied the name Azalea bakeri to a small population of azaleas found in Union County, Georgia, and described its province as the Blue Ridge Mountains of Georgia and North Carolina at elevations above 3,000 feet. Hume (1948) subsequently transferred the epithet bakeri to the genus Rhododendron .

Since 1955 when Dr. Henry T. Skinner (an early director of the U.S. National Arboretum and expert on the native azaleas of the United States) considered R. cumberlandense and R. bakeri to be different names for the same botanical taxon, the epithet bakeri has been used for the much wider-ranging Cumberland azalea. The native habitat of the latter, according to Kron, extends from "Western most Virginia and eastern Kentucky in the Cumberland Mountains and Plateau, south through Tennessee to northern Alabama, and east of the Tennessee River Valley in the southern Blue Ridge, along the border of Tennessee and North Carolina, south to northern Georgia..." In their respective books on azaleas, Frederic P. Lee (1958) and Fred C. Galle (1987) treated R. cumberlandense as a synonym of R. bakeri . (Galle notes that some observers consider these names to represent different species.) For reasons indicated below, Kron (1993) states that the correct name for the Cumberland azalea is R. cumberlandense , not R. bakeri.

This is not a matter of changing the circumscription of the widely distributed Cumberland azalea familiar to Skinner, Lee, Galle, and thousands of others. It is, rather, the result of applying a taxonomic decision as to the nature of the type specimen for R. bakeri and then following the rules of botanical nomenclature. When a botanist has found a population of plants that he desires to name as a new species, he must publish the identity of a "type" specimen and a description or a "diagnosis" distinguishing the new species from others. The type specimen is usually a dried, pressed specimen mounted on an herbarium sheet and properly labeled with information about the circumstances of collection. The nomenclature rules establish an inextricable link between the name and the specimen designated as the type in the original publication.

The characteristics of the herbarium specimen designated by Lemmon (1938) as the nomenclatural type for R. bakeri are not congruent with those of the large and geographically widespread populations of the Cumberland azalea. Nor, indeed, do the characteristics of the type specimen fit the description published in Lemmon's protologue (Kron, personal communication). Lemmon's herbarium specimen has young expanding leaves, while the flowers on the plant widely recognized as R. bakeri appear after the leaves mature. Kron (1993) noted important morphological differences between Lemmon's specimen and plants of the Cumberland azalea as seen in the field and in dozens of herbarium specimens from all parts of the species' range. She concluded that the Lemmon specimen is from a hybrid population (probably R. flammeum x R. canescens ).

In sum:

• Lemmon & McKay (Lemmon, 1938) based the epithet bakeri on a small population of azaleas found in Union County, Georgia, and the Blue Ridge to North Carolina.

• Following Skinner's 1955 statement equating R. bakeri and R. cumberlandense , the earlier-published name R. bakeri came into widespread use for the Cumberland azalea.

• During her extensive field and herbarium investigations of plants in Rhododendron section Pentanthera (deciduous azaleas), Kron (1993) concluded that Lemmon's herbarium specimen designated as the type for R. bakeri is a hybrid in origin.

• A botanical name is linked to its type. Because the characteristics of the type for R. bakeri are not consistent with those of the species to which the epithet has been widely applied (the Cumberland azalea), the name cannot be used for that species. It must be replaced with the earliest available name, R. cumberlandense .

• Kron has not changed the circumscription of the Cumberland azalea, a taxon long generally known as R. bakeri . It is the same group of plants; only the name has changed.

References
Braun, E.L. 1941. The red azaleas of the Cumberlands. Rhodora 43: 31-35.
Galle, Fred C. 1987. Azaleas . Rev. & enl. ed. Portland, OR: Timber Press.
Hume, H. Harold. 1948. Azaleas: Kinds and Culture . New York: Macmillan Co.
Kron, K.A. 1993. A revision of Rhododendron section Pentanthera. Edinb. J. Bot. 50(3): 309-311.
Lee, Frederic P. 1958. The Azalea Book . Princeton: D. Van Nostrand Co., Inc. [Lee, p. 162, states that his descriptions of the eastern native azaleas are based on Skinner (1955).]
Lemmon, W.P. 1938. Notes on a study of southeastern azaleas with descriptions of two new species. Bartonia 19: 14-17.
Skinner, H.T. 1955. In search of native azaleas. Morris Arbor. Bull. 6:1 5-22.

Acknowledgments
The author is grateful to Dr. Kron for reading this note and suggesting emendations.

Donald Voss is a member of the Potomac Valley Chapter.