Rhododendron (from the Greek: rhodos, "rose", and dendron, "tree") is a genus of flowering plants in the family Ericaceae. It is a large genus with over 1000 species and most have showy flower displays. It includes the plants known to gardeners as azaleas. It's the national flower of Nepal.
The Rhododendron is a genus characterized by shrubs and small to (rarely) large trees, the smallest species growing to 10-100 cm tall, and the largest, R. giganteum, reported to over 30 m tall[1]. The leaves are spirally arranged; leaf size can range from 1-2 cm to over 50 cm, exceptionally 1
00 cm in R. sinogrande. They may be either evergreen or deciduous. In some species the underside of the leaves is 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 section Vireya that often grow as epiphytes.
The Rhododendron is a genus characterized by shrubs and small to (rarely) large trees, the smallest species growing to 10-100 cm tall, and the largest, R. giganteum, reported to over 30 m tall[1]. The leaves are spirally arranged; leaf size can range from 1-2 cm to over 50 cm, exceptionally 1
00 cm in R. sinogrande. They may be either evergreen or deciduous. In some species the underside of the leaves is 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 section Vireya that often grow as epiphytes. Distribution
Rhododendron is a very widely distributed genus, occurring throughout most of the Northern Hemisphere except for dry areas, and extending into the Southern Hemisphere in southeastern Asia and northern Australasia. The highest species diversity is found in the Himalayan mountains from Uttarakhand, Nepal and Sikkim to Yunnan and Sichuan, with other significant areas of diversity in the mountains of Indo-China, Korea, Japan and Taiwan. Rhododendron, also known as "Lali Guras" in local language is the national flower of Nepal and the state tree of the state of Uttarakhand in India. In Korea, Rhododendron schlippenbachii is particularly common (called 철쭉(choltjuk)). In addition, there are a significant number of tropical rhododendron species from sou
theast Asia to northern Australia, with 55 known species in Borneo and 164 in New Guinea. [2] Relatively fewer species occur in North America and Europe. Rhododendrons have not been found in South America or Africa.
theast Asia to northern Australia, with 55 known species in Borneo and 164 in New Guinea. [2] Relatively fewer species occur in North America and Europe. Rhododendrons have not been found in South America or Africa.Classification
The species are organized by subgenus, section, subsection and series. These are currently divided into four large and four small subgenera:
Subgenus Rhododendron L.: small leaf or lepidotes (with scales on the underside of their leaves); several hundred species, type: Rhododendron ferrugineum. The tropical rhododendrons (sect. Vireya, about 300 species) are usually included as a section in this subgenus, but sometimes split off
as a ninth subgenus.]]. Recent genetic investigations have caused an ongoing realignment of species and groups within the genus, and also have caused the old genus Ledum to be reclassified within subgenus Rhododendron. Further realignment within the subgenera is currently proposed [3][4], including the merging of subgenus Hymenanthes into subgenus Pentanthera.
Rhododendrons are extensively hybridized in cultivation, and natural hybrids often occur in areas where species ranges overlap. There are over 28,000 cultivars of Rhododendron in the International Rhododendron Registry held by the Royal Horticultural Society. Most have been bred for their flowers, but a few are of garden interest because of ornamental leaves and some for ornamental bark or stems.
Some species (e.g. Rhododendron ponticum in the United Kingdom) are invasive as introduced plants, spreading in woodland areas replacing the natural understory. R. ponticum is difficult to eradicate, as its roots can make new shoots.
Subgenus Rhododendron L.: small leaf or lepidotes (with scales on the underside of their leaves); several hundred species, type: Rhododendron ferrugineum. The tropical rhododendrons (sect. Vireya, about 300 species) are usually included as a section in this subgenus, but sometimes split off
as a ninth subgenus.]]. Recent genetic investigations have caused an ongoing realignment of species and groups within the genus, and also have caused the old genus Ledum to be reclassified within subgenus Rhododendron. Further realignment within the subgenera is currently proposed [3][4], including the merging of subgenus Hymenanthes into subgenus Pentanthera.Rhododendrons are extensively hybridized in cultivation, and natural hybrids often occur in areas where species ranges overlap. There are over 28,000 cultivars of Rhododendron in the International Rhododendron Registry held by the Royal Horticultural Society. Most have been bred for their flowers, but a few are of garden interest because of ornamental leaves and some for ornamental bark or stems.
Some species (e.g. Rhododendron ponticum in the United Kingdom) are invasive as introduced plants, spreading in woodland areas replacing the natural understory. R. ponticum is difficult to eradicate, as its roots can make new shoots.
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