A New Look at the Azaleas and Rhododendrons of the Blue Ridge Mountains
By David G. Leach
The President of the Southeastern Chapter of the American Rhododendron Society has asked me to write an account of the tour to inspect the azaleas and rhododendrons in the North Carolina mountains which took place in mid June under the guidance of Dr. W. N. Fortescue, a devoted student-and collector of these fine native plants.
President Brooks, Dr. Fortescue and Dr. Ernest Yelton invited a group of northern enthusiasts to visit the Asheville area during the blooming season and to attend a meeting of the newly formed Chapter. Joseph Gable, M. G. Coplen, Lanny Pride, Warren Baldsiefen, Clarence Barbre, Mr. and Mrs. Edmond Amateis and the writer were later joined by Dr. Edgar Anderson of the Missouri Botanical Garden and by S. D. Coleman, the well known collector from Fort Gainer, Georgia. (Fig. 1) Together we enjoyed a memorable week of enthralling and instructive tours in the daytime followed by delightful social entertainments at which the visitors were the guests of Dr. and Mrs. Fortescue, Mrs. Jane Pardee, Dr. and Mrs. Yelton, and the Southeastern Chapter, on successive occasions.
Fig. 1. Visitors and members of the A.R.S. Southeastern Chapter at Biltmore
Estate. Standing, back row, l. to r.: Clarence Barbre, Mrs. Edmond Amateis,
M. G. Coplan, Warren Baldsiefen, Nick Fortescue, Mrs. W. N. Fortescue,
Mrs. Jane Pardee, David G. Leach, Kneeling, front row, l. to r.: Lanny Pride,
Lottie Fortescue, Edmond Amateis, Joseph Gable, Sylvester Owens,
Dr. W. N. Fortescue.
Photo by Dr. Fred Nisbet
With Dr. Fortescue's intimate knowledge of the mountains and the Jeeps which he provided for transportation over rough country we were able to survey the multitudes of azaleas and rhododendrons in astonishing scope and variety, getting a comprehensive grasp of the complex plant populations and enjoying the magnificent spectacles which their flowers provided.
The overwhelming impression of the azaleas is their massive diversity, far surpassing anything that the botanists have led us to expect. The North Carolina azaleas are a vast, amorphous population shifting endlessly in a dynamic evolutionary phase in which crosses in the wild and great masses of natural hybrids are commonplace. A revelation awaits any student of the genus who can visit these mountains with a guide especially interested in azaleas, as we did.
The traveling enthusiast might just as well leave his botanical keys at home. They are useless in any attempt to identify species in countless hybrid swarms which are encountered at every hand. Our first day in the field we inspected the azaleas atop Peachtree Knob, near Maggie, N.C. Here almost the entire plant population consists of yellow or orange-red flowered intermediates between calendulaceum and bakeri, with the addition of long corolla tubes both with and without hairs and glands, in about a third of the scarlet flowered plants. The long, hairy non-glandular tube is normally diagnostic for speciosum and is, in fact, the principal botanical means of distinguishing this species from calendulaceum. Yet the nearest speciosum is almost a hundred and fifty miles to the South, in central Georgia. The influence of its characteristics has apparently been transmitted through gene exchange originating at that distance and being passed on progressively farther north into the heart of the North Carolina mountains.
Dr. Anderson had a somewhat different view. Later he subjected the azaleas on Peachtree Knob to his celebrated method of population analysis and concluded that it derived from two sources: a calendulaceum-like forbear with glabrous leaves bearing flowers in the yellow to orange range with a short, expanded corolla tube, wide recurved lobes and with triangular calyx lobes; and from a bakeri-like antecedent with hairy leaves and flowers in the pink to red range with a long, narrow corolla tube and narrow, straight lobes, and with obtuse calyx lobes. Perhaps this still would not rule out the speciosum influence which seemed to me so clear if either speciosum or bakeri were a primeval contributor in the evolution of the other, or if both had a common long-tube ancestor. Dr. Anderson left for Abyssinia shortly after the North Carolina tour and I have not had a chance to discuss it with him.
In any case, I have long wondered why the azaleas which are such a conspicuous feature of the southeastern flora have been so inadequately studied by botanists. Here is an enormous group of important plants which seem to have been shunned, and I was beginning to understand why. They are a geneticist's dream, but they are a taxonomist's nightmare.
A quick look at the azaleas bordering Mile High Road and Poco Gap confirmed the distribution of intergrades between calendulaceum and bakeri over very large areas of the mountains, though a much larger proportion of the population at Poco Gap resembled typical calendulaceum.
Perhaps the most interesting site of those we visited was a trail near Franklin, North Carolina where we encountered, in less than a mile, a dazzling and bewildering spectacle of azaleas in flower in every conceivable shade from buff to deep yellow; from pale pink to electric scarlet; from white to deep orange, and with innumerable pastel blends of all of them. Here was hybridity run wild in a gigantic melee of intermingling species arborescens had joined the scene.
First there was orange and yellow calendulaceum crossed with scarlet bakeri, producing the range of natural hybrids familiar from our tour of Peachtree Knob. But this was only the beginning. Calendulaceum had also crossed with white arborescens, producing the buffs and light yellows. Scarlet bakeri had crossed with arborescens, producing an appealing range of pinks. Then the calendulaceum-bakeri swarms had crossed with the calendulaceum-arborescens and bakeri-arborescens hybrids resulting in the kaleidoscopic array of both vivid and pastel colors which made the trail an idyll in the wilderness. Many of these azaleas were extraordinarily beautiful, of the greatest value for garden decoration, and I thought to myself how rewarding an intensive breeding project concentrated solely among the eastern American azaleas would probably be.
I took the color photograph reproduced on the front cover of this issue of the "Bulletin" to show just a random selection of the species and natural hybrids encountered on a short section of the trail. Shown here are a double flowered form of bakeri, typical calendulaceum, bakeri and arborescens, together with a pink bakeri-arborescens hybrid, an ivory calendulaceum-arborescens hybrid and an orange-red calendulaceum-bakeri hybrid. This, at least, is their predominating parentage. Probably the hybrids are of a more advanced generation, intricately crossed and back-crossed.
The trail with its pastel rainbows from the Azaleas towering overhead had still another wonder in store for us before we left it. A spectacular colony of calendulaceum with mammoth orange flowers was encountered, the huge blossoms glittering in the sunlight filtered through the trees seeming unreal in that sylvan setting, as if a plantation of the finest Exbury hybrid Azaleas had been set down in this quiet woodland. The largest flowers measured almost three and a half inches in diameter. The top lobe was yellow, almost entirely so, forming a golden shield in fetching contrast to the gargantuan orange lower lobes. A single truss of five flowers more than filled a cupped hand. This is incomparably the finest form of calendulaceum that has ever come to my attention. It should be propagated for commercial distribution. It should also be the subject of a cytological study.
Our next stop in the tour as dusk was falling was Wayah Bald, elevation about 5400 feet. Here was a return to familiar ground, the white Azalea flowers in the failing light shining out like myriad earth-bound stars on the mountain top. This was arborescens var. richardsonii, pure, constant and recognizable without hesitation, a rather satisfying landmark in a sea of disconcerting anomalies.
Our survey of the native Azaleas ended the next day with a visit to the incomparable collection of the late Chauncey Beadle, at the Biltmore Estate, just south of Asheville. There, in the affectionate care of Sylvester Owens, is a magnificent array of extraordinarily fine forms of all of the American species together with many natural hybrids, painstakingly assembled over a period of many years. Oblongifolium, arborescens, bakeri and so-called furbishii (about which I mean to write a note for a future "Bulletin"), were all in bloom in an assortment of outstanding ornamental forms. The garden features the southeastern Azaleas which Mr. Beadle gathered himself in countless journeys through Georgia, North and South Carolina, Tennessee, Kentucky and the Virginias. It is interesting, and sad, to reflect that Mr. Beadle never published the book on native Azaleas on which he worked for many years. The stunning watercolors intended as illustrations are in the Smithsonian Institute in Washington but Mr. Beadle could never bring the work to an authority and finality equal to his high standards. These brilliant multitudes of Azaleas, elusive and shifting as quicksilver, finally defeated his devoted effort to reduce their diversity to identity, and he died believing his manuscript not ready for publication. The American Rhododendron Society might determine the condition of the manuscript and investigate the possibility of obtaining financial backing from such an institution as the Longwood Foundation for the publication of this work, illustrated with the watercolors now at the Smithsonian Institute.
Dr. Fred Nisbet, superintendent of Biltmore Estate, which is open to the public for a small admission charge, informed our group of his intention to assemble there a large collection of Rhododendrons, extending even to tender epiphytes for planting in the conservatory. In the climate of the North Carolina mountains it should be possible to create a collection unrivaled in size and variety in the eastern United States. The frost-free growing season is almost identical in length with that of Corvallis, Oregon, for example, and the average January temperature is only four degrees colder. Such a demonstration will add immeasurably to the horticultural resources of the whole southern Appalachian region, where the Asian Rhododendrons and their hybrids are all but unknown.
The June tour with guides both interested in Azaleas and familiar with the mountain wildernesses gave me an entirely different impression than any I had obtained from previous, more superficial visits to the North Carolina mountains. The larger impact of great masses of Azaleas in flux was overwhelming, the evidence indisputable. The species in typical form are often conspicuous by their rarity as they stand out in vast seas of Azaleas undergoing introgressive hybridization. There need be only the opportunity of proximity for the species to cross in the wilderness on a colossal scale. No real intimation of the magnitude and frequency of this occurrence has been published, to the best of my knowledge. The populations often fail completely to fit into the convenient categories we call species, the intergrading hybrids constituting uninterrupted progressions of microforms linking their forbears.
In an evolutionary sense it is a recent and continuing process, not a phase which is reaching toward a conclusion. The internal genetic barriers to hybridization are weak, the characteristics from the ancestral species tending not to retain their original association for the production of more or less clearly defined subspecies. Neither do the new hybrid races seem to be at any selective disadvantage in their gene combinations. Analyzing some of the sites we visited, it seems that the older progenitors which produced the hybrid populations are less well suited to their environment than their descendants. In their diminishing numbers they give evidence of lacking any adaptation to their way of life which would place them at a selective advantage.
Our week's tour approached its end with a visit to the summit of Roan Mountain for a view of the famed mass display of R. catawbiense to be seen in bloom there. No advance description could equal the magnificent spectacle of lavender-pink flowers in a vast billowing sea reaching out to the misty violet horizon of the mountains. Surely this is one of the great floral scenes of the nation, a vista of immense drama in a majestic setting.
Individually, the great old plants in the fully exposed meadows are faultless mounds of handsome foliage, up to ten feet tall, each. a giant bouquet studded with countless flowers which often all but concealed the leaves. They seemed considerably more compact than plants of the species we had seen at lower altitudes and there was little variation in the color of the flowers. An interesting mutation showed itself in a group with staminoid flowers consisting of fifteen stamens and a stigma, without a corolla. The five lobes of the corolla had been converted into stamens, making an exotic feathery formation in lieu of the usual flower truss.
Our tour concluded with a trip to a remote mountain to see the red-flowered maximum about which eastern fanciers have been hearing for several years. This species has been known heretofore only in white and in shades of pink, and I was especially eager to examine the rarity which we had been promised would be seen later in the week.
As we slowly made our way toward the site Dr. Ernest Yelton, one of our guides, exhibited his fantastic ability to pass through the all but impenetrable underbrush at a fast gallop, an exhibition of split-second writhing that would blench the cheek of either an All-American fullback or a fan dancer. But the Rhododendron we sought turned out to be strange indeed, so permeated with red pigment that the sap looked like blood. The cambium of the plant is red, the buds are red, the petioles and leaf veins are red, and the pedicels and flowers are red. Looking at the newly formed leaves against the light shows a bold red blotch in the center of each. This is a unique rhododendron, possessor of a concentration of pigment hitherto unknown in the genus.
Color in rhododendron flowers is normally determined by plastid pigments, ranging from colorless through shades of cream to yellow, which are found in the tissues of the corolla. They are not soluble in sap. Other pigments soluble in the cell sap are the yellow and ivory-white flavones and flavonols, and the red and blue anthocyanins. Together these in various combinations produce the flower color. It is an interesting speculation as to what happened to produce the strange red maximum. The supply of pigment in Rhododendrons is not inexhaustible. If a great deal of flavone is produced there is an automatic reduction in the amount of anthocyanin. Just the opposite seems to have occurred here. The anthocyanin is present in unprecedented amount, possibly resulting in the total absence of other pigment.
With this interesting enigma lingering in our minds we concluded a week of uninterrupted pleasure, thanks to the generosity of time and the warm hospitality which our North Carolina hosts bestowed upon us. None of us will soon forget the attention and thought that was devoted to our tour by Dr. Fortescue, his son Nick and his charming wife and daughter; and by Dr. Yelton, Mrs. Pardee, Joe Brooks and others who made our journey a memorable experience.