The Rhododendron is an interesting genus characterized by shrubs and small to (rarely) large trees, the smallest species growing to 10-20 cm tall, and the largest, R. arboreum, reported to 50 m tall. The leaves are spirally arranged; leaf size can range from 1-2 cm to over 50 cm, exceptionally 100 cm in R. sinogrande. They may be either evergreen or deciduous. In some species the underside of the leaves are covered with scales (lepidote) or hairs (indumentum). Some of the best known species are noted for their many clusters of large flowers. There are alpine species with small flowers and small leaves, and tropical species such as subgenus Vireya that often grow as epiphytes.
