RHODODENDRON

(Rhododendron), any of a genus of woody plants in the heath family (Ericaceae), notable for their attractive flowers and handsome foliage. The genus is large and extremely diverse, comprising about 800 species. They are native chiefly in the North Temperate Zone, especially in the moist acid soil of the Himalayas, southeastern Asia, and the mountains of Malaysia, where they form dense thickets. The genus Rhododendron includes the azalea (q.v.) species, which some gardeners consider distinct. Rhododendrons range in habit from evergreen to deciduous, from low-growing ground covers to tall trees. The first species available for garden use, in the mid-1600s, was R. hirsutum, the hairy alpine rose, which may grow as high as 1 metre (3 feet). Others range from matlike dwarf species only 10 centimetres (4 inches) high (R. prostratum, from Yunnan, China) to trees in excess of 12 m (R. arboreum, R. barbatum, and R. giganteum, from Asia). Leaves are thick and leathery and are evergreen in all but the azalea species, some of which are deciduous. Flowers are usually tubular to funnel-shaped and occur in a wide range of colourswhite, yellow, pink, scarlet, purple, and blue. The catawba rhododendron, or mountain rosebay (R. catawbiense), of the southeastern United States, is plentiful and a great flowering attraction in June in the Great Smoky Mountains National Park. The hearty catawba hybrids are derived from R. catawbiense and allied species. The great laurel rhododendron (R. maximum), overlapping in distribution with the catawba, ranges more northeasterly; it is often grown as an ornamental. Both can be small trees, up to 6 m or taller. Rhodora (R. canadense), from northeastern North America, bears rose-purple flowers before the leaves unfurl.