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Species In Our Midst
Rhododendron catawbiense

by John Perkins


Rhododendron catawbiense 'Catalgla'
Picture by S & J Perkins
Rhododendron catawbiense 'Catalgla' in Hanson, MA


Rhododendron catawbiense

Rhododendron catawbiense, The Mountain Rosebay Rhododendron, is a elepidote (having no scales) species native to the mountains of Alabama, Georgia, Kentucky, North Carolina, Virginia, and West Virginia growing on summits, rocky ridges, balds, and open areas from 4000 to 6500 feet. The epithet 'catawbiense' refers to the Catawba river, formerly used by the Catawba Indians to travel between the mountains of North Carolina and the Piedmont region of the Carolinas. The species was found on this river in 1809 by John Fraser.

Rhododendron catawbiense and R. maximum, both members of the Section Ponticum, Subsection Pontica, form dense thickets which in pioneer days caused travel across the Appalachian and Allegheny mountains to be very difficult and still provide flora vistas considered to be among the most impressive in the world.

Although normally 3 to 10 feet, R. catawbiense may occasionally be as tall as 20 feet. The plant habit is spreading, broader than tall. The leaves are elliptic to oblong, 3 to 5 inches long, and mostly glabrous having minute hairs only on the whitish lower surface. The branchlets when young, petioles, and flower parts are tomentose.

The inflorescence (truss) of 8-20 open bell-shaped flowers form a candelabroid umbel, blooming May to June. The 5-lobed flower is 1.5 to 2 inches long, lilac-purple to rose, occasionally pink to white in color with faint olive-green spotting. The calyx is minute being much smaller in R. catawbiense than in R. maximum. Hardiness is rated at -20° to -30°F (-29° to -35°C).

Most named cultivars of R. catawbiense were selected as part of hybridizers' search for both hardy red and hardy white hybrid elepidotes. R. catawbiense 'Powell Glass', a white-flowered form, is the most famous having been a parent to several other seed grown white forms of the species as well as several dozen named hybrids. R. catawbiense 'Catalgla', 'Catanea', 'Virgin', 'Clark's White', and 'Labar's White' are other selected white-flowered forms of this species.

Rhododendron catawbiense 'Catby' and the more generic R. catawbiense var. rubra are reddish-flowered forms. R. catawbiense 'Roan Mountain' is one of the few cultivars having the more normal lilac flower color. R. catawbiense var. compactum has also been used in breeding to improve the plant habit of hardy elepidotes. The Insularis Group of this species with larger flowers and leaves is found at lower elevations. R. catawbiense 'Ken's Find' is a white-flowered member of this group. This Insularis Group of R. catawbiense as well as R. hyperythrum are currently being used to breed more heat tolerant hybrids for the southern garden.

No species has been more important in the breeding of cold hardy sun tolerant large-leafed rhododendrons than R. catawbiense. Hundreds of commercial hybrids are at least 50% R. catawbiense and hundreds more have at least some R. catawbiense in their parentage. Eastern hybridizers such as Gable, Pride, Delp, Shammarello, Leach, Mezitt, Mehlquist and Blough relied heavily on this species attempting to improve on the fine R. catawbiense hybrids, the so called "Ironclads", produced by Waterer (England) and Siedel (Germany) in the 19th century.

Hybrids such as 'Belle Heller', 'Ice Cube', 'Henry's Red', 'Joe Paterno', 'Lodestar', 'Tony's Gift', and 'Vinemount' maintain the best characteristics and look of R. catawbiense while reflecting the breeding goals of the various hybridizers that produced them.

'Catawbiense Album', 'Catawbiense Boursault', and 'Catawbiense Grandiflorum' are confusing names because they are not the pure species but hybrids of R. catawbiense. Nowadays, new hybrids are not allowed to use a species in its name.

Natural hybrids between R. catawbiense and R. maximum occur in the wild where their ranges overlap. The well known 'Russell Harmon' may be an example of such an occurrence. Moreover, R. catawbiense has been successfully crossed with all of the other members of the subsection Pontica and many members of the section Ponticum.

Being difficult to propagate by cuttings, this species is seldom available from the Chapter's Van Veen order, the Plants-4-Members sale, or local nurseries; however, the better colored flower forms of the handsome R. catawbiense are worth the extra effort required when looking to fill that sunny exposed area in your New England garden.

John Perkins, Salem, NH


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