The Rhododendron calophyllum belongs to Ericaceae (the Azalea family). It is a small evergreen tree that is distributed to Bhutan, northern India, northeast Burma, Sikkim, Thailand, northern Vietnam, and southwestern China. This tree grows in mountains at altitudes of 2,600-3,200 m, and can reach 3-6 m in height. The leaves are leathery, lanceolate, oblong-oblanceolate, or elliptic, 5-15 cm long and 2-8 cm wide in size. The flowers are white to pale pink, funnel-shaped, very fragrant, and bloom during May and June.