Species In Our
R. wiltonii is an elepidote (lacking scales) species. It is a member of Subsection Taliensia, a large agglomeration of species that includes the more familiar R. bureavii and R. roxieanum. It occurs in the western parts of Sichuan province in China, where it inhabits thickets and woodlands, as well as cliffs and rocky slopes, at elevations of 8,000 to 11,000 feet. Ernest "Chinese" Wilson first discovered it while exploring China for the Veitch firm in England, in 1904. Wilson collected it also in 1908 and again in 1910, on expeditions for the Arnold Arboretum. The name commemorates Sir Colville Wilton, of the Chinese Consular Service in Ichang.
This species forms a broadly upright shrub, attaining heights of 3 to 16 feet in the wild, generally less in cultivation. The branchlets are coated with a dense brown or whitish tomentum (fuzz). Leaves are oblanceolate (lance-shaped, but with the narrower end near the stem) to broadly elliptic. They are up to 5 inches long by 1 1/2 inches across, and are held for 2 to 3 years. The upper surface is bullate (with deeply impressed veins), a distinctive diagnostic feature; the lower surface sports a thick, wooly, cinnamon-colored to rusty-red indumentum.
The inflorescence consists of 6 to 10 flowers in a loose truss. The corolla is campanulate (bell-shaped) with 5 lobes, up to 1 1/2 inches long, white to pink in color, and often spotted or blotched red. At 8 years old, my plant has yet to flower, not surprisingly, since like many species in Subsection Taliensia, R. wiltonii may take several years to bloom. Cox states that it can be free-flowering with age, and the beautiful specimen illustrated in his Encyclopedia of Rhododendron Species certainly confirms this.
Greer rates its hardiness at -5°F (-21°C), perhaps somewhat too conservative. My plant has suffered no damage in the 6 winters it has grown outdoors here, with a low temperature of -10°F (-23°C) the first winter.
Altogether R. wiltonii is a handsome plant, worth growing for its distinctive foliage alone, and if planted early enough in one's life, one should live to see it flower like the Cox illustration. For unknown reasons, it seems to have been ignored by hybridizers; Salley's Rhododendron Hybrids, Third Edition, lists not a single hybrid with R. wiltonii in its ancestry.
Dick Brooks, Concord, MA