New Rhododendrons for Our North Atlantic States
By John C. Wister
From the Garden Journal of the New York Botanical Garden
Hybrid rhododendrons of the Catawbiense group have been popular garden favorites along the Atlantic seaboard from Massachusetts to Maryland and Virginia for three quarters of a century. Their fine flowers of white, pink, red, purple and magenta come in late May and early June in the Philadelphia area. Their evergreen foliage is handsome the year round and the plants thrive in full sun as well as in partial shade.
The group gets its name from the purple-flowered species, Rhododendron catawbiense which grows wild in the mountains of Virginia, the Carolinas and Georgia. Little appreciated in this country, plants of this species were taken to England early in the last century and flowered there in 1809. Their good qualities were quickly recognized by keen British gardeners. Two years later, Rhododendron arboreum, a red flowered, tree-like Himalayan plant was brought to England and in 1826 crosses were made between the two species, resulting in hybrids which soon evoked the enthusiasm of British gardeners. Encouraged by the reception of the new hybrids, other crosses were made between R. catawbiense and R. ponticum, a rosy purple species from Asia Minor. Later R. maximum, a late-flowering white species native from Maine to Georgia, was also used as a parent.
American gardeners knew nothing of these new plants until Anthony Waterer, an English nurseryman, brought 1,500 plants to the Centennial Exposition in Philadelphia, in 1876. They created a sensation, were quickly sold, and were followed by larger quantities shipped by Waterer and other nurserymen in the ensuing years. Old collections are to be found around Baltimore, Philadelphia, in the New Jersey and the Long Island suburbs of New York City, in Connecticut, Rhode Island and even in Boston.
In, the 1890's and early 1900's, the largest public collection was at the Arnold Arboretum. Here after long trial, during which many varieties were winter-killed, those which survived were called "Ironclads."
There was little American propagation except by Samuel Parsons on Long Island, he raised several seedlings, plants of which are still grown. Most nurserymen bought young plants in England and Holland and resold them. This continued until importations were stopped by Plant Quarantine No. 37.
When this quarantine went into effect in 1919, there evidently were only two or three American nurseries propagating rhododendrons in any quantity. As these nurseries could supply only a small part of the demand, other nurseries took up the work. Today many thousands of plants are being produced yearly on both coasts, mostly by grafting on ponticum stocks. A few nurseries propagate also by layering. One or two have been successful with stem cuttings and leaf bud cuttings. Most of the varieties grown date back half a century or a century. The few more recent hybrids which are reliably hardy apparently differ little from the earliest ones.
In the first quarter of the present century, a great upswing in the popularity of the rhododendron began in Europe. This was caused by the discovery of hundreds of new species in China and India which, when brought to England, proved hardy in Cornwall and other mild regions. Skilled gardeners, amateur and professional, soon used them for breeding. Their seedlings became the center of attention in flower shows. Hundreds of varieties were named, propagated and introduced into commerce, Some succeeded only in the mildest climates. Others were successful in colder parts of England. A special Rhododendron Society, later affiliated with the Royal Horticultural Society, was formed. Its bulletins praised the new kinds and recommended that the old "Ironclads" be discarded as entirely superseded.
The new kinds were brought to this country, and grew happily in favored sections on the Pacific Coast and in greenhouses. Much to the disappointment of gardeners in the east, they were not hardy here; they could not stand the winters of the Atlantic coast. The "Ironclads" were still the only ones reliably hardy with us.
This situation might have continued indefinitely, had it not been for the interest taken by one New Englander, the late Charles O. Dexter, who had retired about 1920 from his business in New Bedford to build a home and garden in Sandwich on Cape Cod. This property, only a mile or two from the ocean, was cooled by ocean breezes of moist air in summer, and had the extreme cold weather tempered by sea breezes in the winter. It was an ideal place for rhododendrons.
Mr. Dexter chose as his landscape architect, Paul Frost, of Cambridge. Mr. Frost was not only a skilled artist, but a tremendous enthusiast for rhododendrons and azaleas. His planting plans in 1922 included not only the "Ironclads" but many rare species and varieties gathered from a dozen or more sources. The rarest of these came from Leonard Ross, of Taunton, Mass., who had been an intimate friend of Jackson Dawson, the first superintendent of planting and propagation of the Arnold Arboretum, and with whom Mr. Dawson had shared many of the treasures which had come to the Arboretum from all parts of the world.
Another rare group came from the Farquhar Nursery in Osterville on Cape Cod. John Farquhar was a Scotsman who had, after establishing a flourishing seed store in Boston, started a nursery in Dedham, Massachusetts, and later this nursery at Osterville. In it he had planted many rhododendrons he had purchased at Veitch's Nursery in Exeter, England. Most of them were represented as seedlings of the very lovely Chinese species R. fortunei or its close relatives, which had never been considered hardy in New England but had proceeded to grow happily in this mild section of Cape Cod. Before they could be catalogued and offered for sale, Mr. Farquhar died and his company decided not to continue the Osterville Nursery.
Frost had seen how the plants flourished, and in 1922 he persuaded Mr. Dexter to buy many of them. When E. H. Wilson visited Mr. Dexter in 1924, he was astonished to find flowering in America a number of the species he had discovered in China and introduced to Great Britain. At that time, he pronounced this collection of rhododendrons the most notable he had found in this country.
Inspired by Wilson's praise and the spectacular beauty of the new flowers, Mr. Dexter seems to have become a rhododendron breeder almost over night. He built a special greenhouse and by 1928 and 1929 was setting out yearly, in his woodland nursery rows, about 10,000 rhododendron and azalea seedlings. Wilson was already sharing with him seeds of new species received at the Arnold Arboretum.
In 1930, Frost went to England to visit J. G. Millais, the author of the great two volume monograph on rhododendrons. Millais took him to J. C. Williams in Cornwall, planned his trip to other rhododendron gardens and, most important, gave him a letter of introduction to Kew and to Sir William Wright-Smith, of the Edinburgh Botanic Garden. Everywhere, the rarest of rhododendron seeds were thrust upon him.
As a result, Sandwich became a test ground for the possibilities of the Chinese and the Himalayan rhododendrons in our Atlantic seacoast climate. Most of them, of course, proved tender; however, Wilson remarked to Frost that if even one species proved hardy, the effort would have been worth while. Frost thinks that R. haematodes may be that one, but others flourished also and perhaps scores lived long enough to be used in Mr. Dexter's breeding program.
By the early 1930's, Mr. Dexter's place was becoming famous and was visited by many horticulturists. Among them was the late Leonard Barron, editor of the "Garden Magazine," who became so enthusiastic that he persuaded a great amateur gardener, S. A. Everitt, of Huntington, Long Island, to get some of the plants and try them on his wooded hillside. Within ten years, the Everitt place in turn became famous and was visited by horticulturists from all over the country. Gardeners in other parts of Long Island and in adjoining states began to get a few of the best hybrids to try in their gardens.
Today, there are good collections of these hybrids at (1) Henry du Pont's in Winterthur, Delaware, (2) the Scott Horticultural Foundation at Swarthmore College, (3) the Morris Arboretum in Philadelphia, (4) The New York Botanical Garden in New York City, (5) S. A. Everitt's, (6) John Parker's, (7) Henry Phipps', and- (8) Ernest Coe's on Long Island, and, in the most severe climate of all, (9) the Arnold Arboretum. The parent collection (10) in Sandwich, with its untold thousands of plants ranging from a few inches to ten feet in height, remains the greatest in extent and beauty. After Mr. Dexter's death, the property was purchased by Colonel Roy Brown.
For a number of years, the collections just named have been visited by persons interested in rhododendrons. In 1950 a small group of these persons felt that some concerted action should be taken to evaluate the various kinds and to make them better known, so that they could be more widely tested under varying conditions. There was no question about the great beauty of most of the flowers, but there was and there still is every question about the great variation of hardiness among various seedlings of the same general parentage. There is also great variation in such qualities as reliable blooming year after year, good growth of plant, good foliage, resistance to drought, resistance to cold winters or to late frosts, etc.
The members of this small, informal and entirely unofficial committee, which was headed by Clement G. Bowers of Maine, N.Y., a research fellow of Cornell University, and included Donald Wyman of the Arnold Arboretum, Henry Skinner of the Morris Arboretum, Paul Vossberg of the Westbury Rose Co., Westbury. Long Island, and the author of this article, visited last year each of the places named. Their report will be sent to the American Association of Botanical Gardens and Arboretums, and to the American Rhododendron Society, in the hope of pointing out to these two rather new organizations that here on the east coast is a totally new group of rhododendrons worthy of most serious consideration.
No claim is made that these plants will in any way supersede or take the place of the well-known catawbiense hybrids, the "Ironclads" so long tested, so well: known and so important in our gardens. Any such statement must await testing over many years.
Rather it will be pointed out that the value of the new plants comes from the fact that (1) they bloom about two weeks earlier than the "Ironclads," that (2) some of them are much more rapid growers, that (3) their flowers are much larger, that (4) they include apricot colorings not known in the "Ironclads" and that (5) some of them are fragrant. While their hardiness in more severe climates and through exceptionally cold Winters and sudden changes of temperature remains to be tested, they have stood on the Dexter place nearly thirty years, during which time the thermometer has often gone well below zero. They have lived and bloomed on Long Island for over twenty years and at the Arnold Arboretum for nearly as .long. At these three places, they lived through the record-breaking cold of the winters of 1933, 1934 and 1935, during which. time the Arnold Arboretum reported a temperature of 30° blow zero.
While there are, in the ten collections before mentioned, many thousands of plants of all sizes, there has been practically no propagation of selected clone. Nearly all the plants are seedlings. The first exceptions were some plants Mr. Dexter numbered, propagated by layers and sent to Mr. Everitt, who in turn made further layers for a few friends. More recently, Paul Vossberg, of the Westbury Rose Company, has propagated a limited number of plants by stem cuttings.
Most of the plants examined by the informal committee seem to fall into fairly definite color groupings. The whites are very scarce. The greatest number of plants are close to R. fortunei in quick growth and larger fragrant, and rather washy, pale pink flowers. A smaller but still numerous group includes more compact, slower growing plants with beautiful rose pink flowers without fragrance. The reds also are scarce, but there are some wonderful colors among them. The apricots (shades not found in the catawbiense group) are very scarce and the plants bearing flowers of these coloring have relatively poor foliage. All vary in season from two weeks earlier than the "Ironclad" catawbiense hybrids to plants which flower with these old, well-known varieties. Further study will undoubtedly bring to light many minor variations in each of these rough groupings.
In May and June 1950, the informal committee labeled and described about seventy plants. It is hoped these can be propagated and distributed for further study. After some years, the best twenty or twenty-five of the seventy might be named, propagated and distributed to nurseries through the offices of the Rhododendron Society and the Association of Botanical Gardens and Arboretums. If this can be done, a great forward step will have been taken for the horticulture of Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania and some adjacent states in making available valuable new plants, beautiful and fascinating.