JARS v50n3 - Plant Portrait: Rhododendron sargentianum

Plant Portrait: Rhododendron sargentianum
Frank Dorsey
North Vancouver, British Columbia
Canada
Reprinted from the Vancouver Rhododendron Society newsletter, February 1990

Rhododendron sargentianum was discovered by Ernest Henry Wilson in July 1903 and was introduced into cultivation the same year when he sent seed to his employers, the English nurserymen, Messrs. Veitch and Sons. (In some cases many years elapsed between the discovery of the plant by one collector and its eventual introduction by another.) Although Wilson sent back seed in later expeditions (in 1908 and again in 1910) it appears that the plant has not been found by any other collector. (When we speak of collectors we conveniently ignore the natives of the country to which the plant is endemic.) Rhododendron sargentianum is very limited in its distribution in the wild, having been found only in Sichuan in South Central China.

The name "sargentianum" commemorates Charles Sprague Sargent (1841-1927), director of the Arnold Arboretum in Massachusetts. E.H. Wilson had stopped for five days at the arboretum on his first plant hunting expedition to China. A friendship was formed which eventually led Wilson to leave Veitch's (this long established nursery was rapidly declining in importance) and take employment under Sargent. While naming a newly discovered plant after a prospective employer does not guarantee a position, some of our more ambitious members might wish to consider this approach - a sophisticated adult form of bringing an apple for the teacher.

Rhododendron sargentianum will grow to perhaps 60 cm (2 ft.) in height and about the same in width. It is usually seen at about two-thirds this size. Compact in habit, its small, shiny, oval leaves all but hide the peeling bark of the pale brown stem and branches. As with all of the Section Pogonanthum the foliage is markedly aromatic. Aromas are difficult to classify (we don't have an RHS perfume chart). Peter Cox in his book The Smaller Rhododendrons writes of his father's associating certain species with other scents. E.H.M. Cox associated R. sargentianum with pure crushed thuga. Sure enough, there is a similarity between this rhododendron and the pungent Western red cedar.

Despite the growing interest in foliage and growth habit, rhododendrons, species and hybrids alike, stand or fall by their flowers. Clearly R. sargentianum stands high on this count. Its flowering habit is sometimes described as "daphne-like" and certainly there is a similarity. The flowers are usually in clusters of five to seven but occasionally as many as 12. Each flower is about 12 to 6 mm long (½ to ⅔ inch). The colour is white, cream or a pale yellow. Written in such prosaic terms, it really doesn't sound to be an outstanding bloom. But it is. Outstanding not in the flamboyant sense but rather in its perfection and daintiness. I would be an exaggeration to say that R. sargentianum covers itself in flowers. It is, however, a moderately heavy bloomer and, more important, a reliable bloomer. Further, it has the advantage of blooming when young. You can expect flowers from a 2-year-old cutting grown plant.

Rhododendron sargentianum is not a demanding plant. On the very few occasions it was found in the wild it was growing on exposed rocks and cliffs. In the writer's experience, it is quite hardy in our climate. Greer's Guidebook shows it as good to -50°F (-20°C). Davidian in his Rhododendron Species, Vol. 1, Lepidotes states "...hardy in sheltered positions..." It makes an excellent rock garden shrub and is especially well suited to the front of a border. Light shade at the hottest time of day is recommended, but too much shade will reduce flowering and will draw out the growth. Good drainage is essential.

Little use has been made to date in hybridizing R. sargentianum . The only one which comes to mind is 'Sarled', a Collingwood Ingram cross of R. sargentianum and R. trichostomum . [The late James Caperci's 'Liz Ann' and 'Maricee' are listed in Rhododendron Hybrids , Second Edition, Salley and Greer, as forms of R. sargentianum .] Both are very good and, if anything, easier to grow than the true R. sargentianum . 'Liz Ann' has a definite pink tinge while 'Maricee' is cream coloured. Two forms of R. sargentianum have been given RHS Awards of Merit, an unnamed pale yellow and the clone 'Whitebait', a pale primrose yellow.

'Maricee' and 'Liz Ann' are both available from local growers and the form 'Whitebait' is occasionally seen. 'Sarled' does not appear to be commonly in the trade. Rhododendron sargentianum is well worth seeking out. Its size is such that few can say, "I don't have space for another rhododendron."

Frank Dorsey, a member of the Vancouver Chapter, has authored several articles for the Journal, including "Rhododendron kiusianum: Ideal Rhododendron for the Rock Garden" (Vol. 44, No. 1), "Rhododendron keiskei" (Vol. 45, No. 4) and “Subsection Arborea" (Vol. 45, No. 3).