Rhododendron (from Ancient Greek rhdon 'rose' and dndron 'tree') is a genus of over 1000 species of woody plants in the heath family, either evergreen or deciduous. Most species have showy flowers. Azaleas make up two subgenera of Rhododendron. The flowers of some hydrangeas can appear similar to those of some rhododendrons, but Hydrangea is in a different order. The rhododendron is the national flower of Nepal. Rhododendron is a genus characterized by shrubs and small to (rarely) large trees, the smallest species growing to 10100 cm (3.939 in) tall, and the largest, R. giganteum, reported to over 30 m (98 ft) tall. The leaves are spirally arranged; leaf size can range from 12 cm (0.390.79 in) to over 50 cm (20 in), exceptionally 100 cm (39 in) in R. sinogrande. They may be either evergreen or deciduous. In some species, the undersides of the leaves are covered with scales (lepidote) or hairs (indumentum).
Contributions by Dunning, MPF, and Jesup.