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Species In Our Midst
Rhododendron kiusianum
by John and Sally Perkins
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Rhododendron kiusianum, a member of subgenus Tsutsusi section Tsutsusi, is native to southern Japan growing in open woodlands on hillsides at elevations of 1800-2400 ft. It was known to the Japanese for centuries before being botanically described by Makino in 1914. Natural hybrids involving R. kaempferi are common where the two species overlap in southern Japan. This may explain why experts sometimes disagree on key characteristics when describing this species. The epithet kiusianum refers to the Japanese island of Kyushu.
The plant habit is spreading, densely branching reaching 2 feet (0.6 m) high. Young shoots, leaves, and flowers are covered with red-brown hairs. The leaves are oval-obovate 0.5-2.0 x 0.2-1.5 cm. The funnel shaped flowers in trusses of 2-3 have 5 stamens and are usually rose-pink but the color ranges from rose to deep purple, rarely white. Hardiness is rated at -10°F(-23°C). It is offered through the Chapter VanVeen order and is often available in the Plants-4-Members sale. This species, with proper siteing, has been successfully grown in USDA zones 5-7 by Chapter members but the information is "word of mouth".
The Japanese have selected and named more than 40 cultivars of this species (See the book Azaleas by Galle). The kurume hybrids heavily depend on R. kiusianum var. sataense which may be a stable hybrid population containing R. kaempferi. Some of the more unusual color forms of R. kiusianum may have at least some R. kaempferi in their background.
`Komo Kulshan' is a American selection of the species. `Pink Clusters' is a Weston Nursery selection containing R. kiusianum.