The "Tougoku-mitsuba-tsutsuji" (Rhododendron wadanum) belongs to Ericaceae (the Azalea family). It is a small deciduous tree that is distributed southward from Miyagi-Yamagata prefecture to eastern Kinki district, the Pacific Ocean Side of Honshu in Japan. This tree grows in montain ridges or forests, and can reach 2-4 m in height. The young branches are pale brown to brown, glabous and glossy. The leaves are broad ovate-diamond and arranged in three whorles at the terminal branches. The 1-3, magenta flowers bloom at the tips of branches from April to June. The corolla is broad funnel-shaped and diveded into five clefts. The flower has ten stamens.