JARS v42n2 - White Catawbas - A Recounting, New Forms

White Catawbas - A Recounting, New Forms
Reid Bahnson, M.D.
Winston-Salem, North Carolina

Fraser's Discovery
John Fraser, the indefatigable English plant explorer discovered Rhododendron catawbiense on the top of Roan Mountain (North Carolina-Tennessee) in 1799. He sent it back to England in 1809 where it was used in early hybridization. One of three native American elepidote species, R. catawbiense is normally distributed in the Southern Appalachian Mountains at high elevations from 3000 to 6400 feet. Its blossoms create vivid displays in mid-June on mountain-top balds at well known sites such as Roan Mountain, Craggy Gardens in North Carolina, and Mount Rogers in Virginia.

Catawba Hybrids
Early breeders recognized the quality of R. catawbiense and created a race of hardy hybrids, crossing it with the then available species of R. maximum , the "Rose Bay of the Carolinas" sent to England in 1736; R. ponticum from Gibraltar and R. caucasicum , from Asia Minor. R. arboreum , introduced into England from India in 1811 (blooming in 1825) though tender, was able to contribute its red color.

It is fortunate that the Waterers, and others in England, Holland and Germany worked with hardy parents. Though hardiness was not essential for the English climate, hardy plants when introduced back into the United States on the East Coast in 1876 were received with enthusiasm and were subsequently widely distributed. Their popularity continues today.

Catawba hybrids, a number of which are over a century old, continue to form the base of commercial landscape rhododendrons in the Eastern United States. They have earned this reputation because they are adapted to the climate and are "good doers". Plant habit and size is more desirable and flowers are larger than R. maximum hybrids. It is acceptably heat tolerant. Rhododendron catawbiense has the significant undesirable characteristic of a blue overcast flower color, which is passed on to its progeny.

White Variants

Recognizing the fault of bluish flower color, rhododendron enthusiasts and breeders seized upon the rare discovery of naturally occurring white variants in the hope of breeding clear pinks, pure reds, and possibly the elusive hardy yellow. Joe Gable acquired a white form from Powell Glass who had "found, collected and moved" seven white Catawbas in the mountains of Virginia (3). He selfed this white and produced 'Catalgla'. Guy Nearing termed his plant of the same line 'Catanea'. Others have continued to self multiple generations in search of a pure white since 'Catalgla' does throw some lavender in its progeny.

'La Bar's White' was collected in the 1950's out of flower in the North Carolina mountains (4). It was likely a "cut back", a mature plant dug in the wild, cut back to the plant base and growing in a nursery from a mature root system rapidly producing a more shapely, desirable and salable plant. (This practice is still common in the North Carolina mountains.) The plant subsequently flowered in La Bar's Stroudsburg, Pennsylvania, nursery and was discovered by Russell Harmon, a son-in-law of La Bar. It was difficult to root and was propagated by layers.

In contradistinction to 'Catalgla', 'La Bar's White' is pure white in bud and lacks color in the flower parts. It qualifies to be correctly termed R. catawbiense var. album . (The English "ironclad", 'Catawbiense Album', is considered to be a hybrid.) The significance of R. catawbiense var. album as a parent is just now beginning to be fully realized through the release and wide distribution of the David Leach hybrids. These plants are not only adapted to the rigors of the East but are also superior and desirable plants in the more equitable climate of the cool, wet Pacific Northwest.

New Forms - 'Clark's White'
Interestingly La Bar's Nursery again enters the scene. In the 1960's a Catawba cut back bloomed white in La Bar's nursery in Avery County, North Carolina. The nursery superintendent, Obie E. Clark, realized its desirability and acquired it personally by exchange. The writer learned of a "white purple laurel" in 1971 and purchased two layers from Clark. ( R. catawbiense is termed "purple laurel" in the mountains, R. maximum is called "big laurel" or "pink laurel" and Kalmia is termed "ivy.")

On flowering pure white it was crossed with other parents. Seed was sent to the ARS Seed Exchange and crossed with 'Phyllis Ballard' (74-516), this bloomed peach pink and apricot without magenta overtones. Weldon Delp (5) used this cross in a number of hardy hybrids for yellow.

'Clarks White' selfed produced four (100%) white offspring identical to the parent. The flower is pure white with a gold blotch with pure white buds. The parent plant continues to grow and flower vigorously. It is extremely difficult to root, with one success in fifteen years by skilled propagators and myself. It is being prepared for tissue culture and is being registered.

'Clark's White' is of medium size, 6' x 7' after 20 plus years, hardy to at least -25° F and flowers at 3500 feet elevation in late May. The truss is dome shaped, 5" wide by 4" high. The corolla is pure white, 2⅜" across, 1¼" in length with 5 lobes. The flower is openly funnel shaped. There is a gold dorsal blotch. The average leaf is 4" long by 1¾" wide and elliptic in shape. Buds and flower parts are pure white.

Lowland White Catawba - 'Ken's Find'
Although typically a mountain plant R. catawbiense appears as disjunct populations at lower elevations in Virginia, North Carolina, and Georgia (6). Found in central North Carolina, Orange County, at 500 feet it was termed R. catawbiense insularis by Coker (7) in 1919. A skilled botanist, his opinion was that this was a distinct form noting that the mountain leaves were 2.4 times longer than broad, but the lowland plant leaves averaged only 1.9 times longer than broad. A number of locations in North Carolina were described by Coker.

A well known bluff termed Flower Hill is located in Johnston County, North Carolina, elevation 220 feet, in the coastal plain. Approximately two acres of R. catawbiense grow on a very steep hillside, with a northern exposure, above a swampy creek. A pure white, white budded form, was discovered here by Ken Moore, Superintendent of the North Carolina Botanical Garden, during the course of a tour by students and gardeners.

In addition to being pure white and very likely retaining its hardiness, it should also be heat tolerant. The type plant remains on the site, pinpointed but not marked for fear of damage or removal. It is in tissue culture, has been propagated and is being registered.

An off white form with lavender tinted parts and a nice pink form (65C RHS, 2.5 RP 8/5 Nickerson light purplish pink) were also found. The typical flower is lavender pink similar to its mountain cousin.

'Ken's Find' is a moderately tall 6' to 8' sparse plant growing in the wild under high shade. Leaves are 4" to 5" long, 2¼" to 2¾" wide, broadly elliptic. Corolla is pure white, 2⅜" x 1½", five lobed, openly funnel shaped. The truss is dome shaped, somewhat lax, 5" to 6" across, 3¾" high, 8 to 10 flowers to the truss.

Off White Forms - Low Elevation
A white form of Catawba had previously been discovered in Stokes County, North Carolina at Hanging Rock State Park (6). It was thought to have perhaps been found in the wild and moved to its site near a park building. The writer learned independently of the Sauratown Mountain plant and since it was on state property requested and later received permission from state authorities to collect, pollinate and propagate this plant. Careful scrutiny of the area at 1500 feet elevation revealed nine distinct and separated white clones in 1986 and an additional six forms in 1987, all growing in an area of typical purplish pink R. catawbiense .

The plants are widely separated by as much as several hundred yards on a northwest facing hillside. (Note: This same general area is the collection site of Kalmia latifolia - 'Shooting Star'.) With the exception of one clone, all flowers were tinted faintly with lavender on the edge of the tepals and/or filaments, anthers. One clone, Saura No. 5 was pure white, but it has not been seen in bud to observe whether it has any color. Attempts were made to propagate by cuttings and grafts one-half of the forms. Four clones have rooted and are growing.

Norris Run Catawbas - Diverse Color Forms
Display of the Sauratown Mountain trusses at our Rhododendron Show in early May 1986 brought word of white forms in southwestern Virginia. This area was investigated with the aid of Earl Crumpton, Blackburg, Virginia in late May 1987. A most delightful surprise was in store, for not only were additional white varieties found, but there was a most diverse display of color forms in one location.

The search for white Catawbas was completely overshadowed by the numerous and varied naturally occurring color forms of R. catawbiense . Where diversity of species occurs there is always the rightful concern of admixture from outside sources. This location, and others described above, is rural, remote, on an unpaved road, with no evidence to suggest that non-indigenous rhododendrons could be any closer than five or more miles.

Located at 1900-2000 feet elevation along Norris Run in western Montgomery County, Virginia, Catawbas are spread along over a half mile or more of north facing hillside. The collection site had been cut over several years before. Plant habit, leaf size and blooming period were typically Catawba.

Irrespective of color, truss size and flower shape were largely similar. Some flowers tended to be more cup shaped. In others gold blotches were prominent. The predominant flower was purplish pink but there were lighter pinks, lovely lavenders and lilacs of varying shades, a vivid red and eight off whites.

All of the whites were tinted with color at the edge of the tepals and/ or the flower parts. The red (66C RHS) had flowers 2½" wide, 1⅜" deep. It could rightfully be termed R catawbiense var. rubrum . Several outstanding plants were tagged (since it is a protected site) and attempts will be made at propagation. The red should be useful for hybridization.

Conclusion
White forms of R. catawbiense should be of value in hybridizing. A pure white form with white buds should allow more clear hardy pinks, pure reds, and development of hardy yellow. 'La Bar's White' is preferable to 'Catalga' for flower color. A new pure white form, 'Clark's White', and a lowland white form, 'Ken's Find', are described. A melting pot of color is described from southwestern Virginia with an improved red form of Catawba.

References
1.  Leach, D.C., Rhododendrons of the World . 1961.

2.  Bowers, C.G., Rhododendrons and Azaleas . 1960.

3.  Livingston, P.A. and West, F.H., Hybrids and Hybridizers . 1978 p. 59, 249.

4.  Personal communication, with gratitude, David C. Leach, August E. Kehr, George Miller, William Fetterhoff, Mrs. John F. Knippenberg.

5.  Salley, H.E., and Greer, H.E., Rhododendron Hybrids . 1986, p. 375.

6.  Schwind, R.L., Rhododendron catawbiense at Low Elevations, ARS Bulletin Vol. 25:3 (1971) p. 180, Vol. 26:4 (1972) p.257.

7.  Coker, W.C., "Distribution of Rhododendron Catawbiense". Journal of Elisha Mitchell Society 35:76-87. Oct. 1919.

Dr. Bahnson is a member of the Piedmont Chapter. He has been interested in and working with hybridizing R. catawbiense var. album since 1971. During the past several years, he has come across additional white forms of Catawba.