The Blue Ridge Parkway - Nature's Rhododendron Alley
Natural Resource Management Specialist
Blue Ridge Parkway
The Blue Ridge Parkway is a 470-mile scenic road that connects Shenandoah National Park in Virginia with Great Smoky Mountains National Park in North Carolina and Tennessee. The road winds along the ridges, gaps, slopes and valleys of the Blue Ridge, Black, Craggy and Plott Balsam mountain ranges through some of the most ecologically complex habitats in the world. The Parkway supports a rich profusion of trees and plants numbering close to 1300 species. Of these, more than 20 plant species are considered rare and appear on threatened or endangered species lists for Virginia and North Carolina.
The complex and unique habitats of the Southern Appalachians provide the proper combination of soil conditions to support a variety of wild rhododendrons - cool and moist, but not soggy, acidic (pH generally 4.6 to 5.4), and shallow with adequate aeration about the roots. Eleven varieties of the genus Rhododendron are known to occur along the Parkway: Rhododendron arborescens, R. ashleyi (syn. maximum), R. calendulaceum, R. catawbiense, R. carolinianum, R. maximum, R. nudiflorum, R. prinophyllum (syn. roseum), R. vaseyi, R. viscosum, and 'Wellesleyanum'. All of these plant varieties are Southern Appalachian endemics; that is, natural populations of these plants can only be found in the Southern Appalachian mountains.
The Parkway provides easy access to the many showy displays of rhododendrons that, heretofore, were only available to the robust and hardy hiker. Throughout the year exquisite floral displays dot the Parkway roadside and trails, but none is more spectacular than the exhibition of the Southern Appalachian heath family in late spring.
Because of the change in elevation all along the Parkway, bloom dates for the various rhododendrons are difficult to pinpoint. However, because of this altitudinal relationship with bloom, visitors to the Parkway can generally observe showy displays for a longer period of time.
In early April, the first of these showy plants blooms. R. nudiflorum, pinxter flower, bears a pink flower. Although not common along the Parkway, some especially showy displays are scattered in wooded areas of Virginia between mileposts 146 and 217, and in North Carolina at milepost 240.3.
Following in quick succession are the pink blooms of R. minus, Carolina rhododendron, which are scattered along the roadside in North Carolina between milepost 308-310 and 404-411.
For a brilliant change of pace, mid-May brings the oranges and yellows of R. calendulaceum, flame azalea. Like rays of sunshine on a rainy day, flame azalea offers a splash of roadside color from Roanoke, Virginia (milepost 130) to Mt. Pisgah, North Carolina (milepost 408). Very few flame azalea shrubs are found north of Roanoke. Unlike most in the heath family, flame azalea are deciduous.
The next to enter the scene, and considered by many to be the most showy of the wild species, is R. catawbiense, catawba or purple rhododendron. The purple rhododendron, scattered all along the Parkway in North Carolina, begins to bloom in early June with the climax occurring at Craggy Gardens (milepost 364) between June 18 - 22. Other excellent displays in North Carolina include the roadside between Gillespie Gap (milepost 330.9) and Mt. Mitchell (milepost 355), the Mt. Pisgah area (milepost 408), and Graveyard Fields (milepost 418.8). Although scattered throughout Virginia, good displays occur at Bald Mountain (milepost 20.7), between Apple Orchard Mountain (milepost 76.3) and Stony Creek (milepost 81), and at Sweet Annie Hollow(milepost 138.6).
The first three weeks in July bring on the more subdued blooms of R. maximum or rosebay rhododendron. This white bloom is relatively rare in Virginia with the most northerly location along the Parkway occurring at Pine Spur Gap, milepost 144.4. Examples of rosebay rhododendron can also be viewed scattered along roadside and trails throughout North Carolina.
Less showy and prevalent on parks lands are R. viscosum, swamp azalea, and R. arborescens, smooth azalea. Both are somewhat late in flowering (June and July) and inhabit bogs and steam margins in both Virginia and North Carolina.
Among the rhododendron varieties considered rare are R. ashleyi, 'Wellesleyanum', R. roseum (election pink), and R. vaseyi (pink-shell azalea). Rare enough to require some legal protection, R. vaseyi, pink-shell azalea, is listed as a "Special Concern" species on the North Carolina Endangered, Threatened and Rare Plant List. Regular population monitoring is required by Parkway natural resource managers and state botanists for long-term protection.
R. prinophyllum (syn. roseum), election pink, is also on the North Carolina state list as a "Significantly Rare Species." While a ranking as significantly rare affords less protection than a listing as special concern, the status of election pink is reviewed every several years to determine whether further field monitoring and protection is needed.
R. ashleyi and R. maximum do not receive legal protection but are found in limited distribution on park lands. R. ashleyi is actually a mutant of R. maximum, rosebay rhododendron; and 'Wellesleyanum' is a natural hybrid of R. catawbiense, purple rhododendron. These two varieties occur together in only one location along the Parkway in North Carolina.
Another phenomenon common to the Southern Appalachians and evidenced along the Parkway are heath "balds," areas of rhododendron in an otherwise unbroken forest (Brooks 1965). Heath balds usually occur on south-facing ridges with shallow soils at elevations above 4500 feet. They are dominated by shrubs of the Ericaceae (heath family), primarily purple rhododendron. The best example of a heath bald on parkway lands is Craggy Gardens at milepost 364 in North Carolina.
While many theories exist on the origin of these balds, almost all agree that maintenance (continuation) of the balds through the years has involved human intervention, either through burning, cutting or grazing. Several of the most quoted theories that have been applied to the origin of the heath balds include:
(1) Cain(1930) who believed heath balds were created by natural disturbances, such as fire, windfall, landslides or a combination of these disturbances;
2) Wells (1936) who attributed heath bald origins to Indians burning mountain summits for wild game enhancement (increased edge-effect) and for campsites; and
(3) Billings and Marks (1957) who felt that increased warming 8500 to 4000 years before present forced spruce-fir forests to retreat to elevations above 5500 feet where a cooler environment permitted survival. This upward movement eliminated spruce-fir on those peaks below 5500 feet, such as Mt. Pisgah (milepost 408). When the climate cooled again and the spruce-fir forests migrated back down to lower elevations (4500 feet), bald communities were created on those peaks where the spruce-fir was eliminated.
Parkway managers are investigating methods and techniques for rhododendron/balds management at Craggy Gardens (MP 364). Past research investigators have concentrated on determining the succession rate and succession species in the vicinity of Craggy Gardens. Current management efforts are concentrating on determining maintenance techniques including grazing, burning and thinning. Since this is considered long-term research, management decisions are not expected during this decade.
And, as if the sheer beauty of wild rhododendrons and the unique phenomenon of heath balds were not enough to tantalize our senses, the presence of certain heath communities are now allowing paleoecologists to document the antiquity and vegetational history of some heath balds through pollen analysis. Flat Laurel Gap Bog (Pisgah Campground) at milepost 408 bears the distinction of being the oldest dated Southern Appalachian mountain bog/heath community, dating back over 3000 years before present (Shafer 1986). The bog in which the heath community grows has accumulated sediment over thousands of years and provides the chemical environment suitable for preservation of pollen.
One can travel the world over and never experience the beauty of the Southern Appalachian rhododendron. So, please come join us next spring, won't you.