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Species In Our Midst
Rhododendron racemosum

by Dick Brooks

Rhododendron racemosum
Picture by S & J Perkins
Rhododendron racemosum in Concord, MA

Rhododendron racemosum

This species is a member of Subsection Scabrifolia, a small group of lepidote rhododendrons native to Yunnan, Sichuan and Guizhou provinces in China. R. racemosum occurs in open terrain, margins of forests and rocky slopes, at elevations from 2,500 to 14,000 feet. It was introduced to western horticulture by the French missionary Père Delavay in 1889. There have been numerous collections and reintroductions since that time.

R. racemosum is most often seen in local gardens as a fairly low growing shrub, to 3 feet or less. However, it is highly variable in plant habit; some very compact forms will scarcely attain 1 foot at maturity, while others will become tall leggy shrubs of 12 feet or more. The leaves are broadly obovate to oblong-elliptic, up to 2" long and 1" wide. They are glabrous (hairless) on both surfaces, and the lower surface is glaucous (with a grayish waxy bloom) and densely scaly.

The inflorescence is unusual in that the flowers develop not only from the terminal bud of the previous season's shoot, but also from axillary buds in the uppermost leaves of the shoot. The inflorescence thus takes on the appearance of a raceme, from which the species derives its name. Individual flowers are small, usually less than 1 inch in diameter, but they occur in such profusion as to cover the plant. They vary in color from white to various shades of light to deep pink. In our area of New England flowering usually occurs in early to mid May. Greer puts its hardiness at -5°F.

This is a first-rate garden plant. Some selections have been made for superior ornamental characteristics: 'Rock Rose', with reddish-purple flowers, and 'White Lace'. The clone 'Pride of Split Rock' is generally presumed to be a hybrid.

R. racemosum has been extensively used by breeders to develop low-growing, floriferous hybrids. Some of the more familiar of these are 'Ginny Gee' SPA (Superior Plant Award), 'Mary Fleming', 'Fairy Mary', 'Vinestar', 'Rik', 'Tom Koenig', 'Pioneer', 'Windbeam' and 'Veesprite'.

Dick Brooks, Concord, MA.

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