Rhododendron

This article is about the plant. For the place, see Rhododendron, Oregon.

Template:Taxobox begin Template:Taxobox image Template:Taxobox begin placement Template:Taxobox regnum entry Template:Taxobox divisio entry Template:Taxobox classis entry Template:Taxobox ordo entry Template:Taxobox familia entry Template:Taxobox genus entry
Template:Taxobox authority new Template:Taxobox end placement Template:Taxobox section subdivision

Azaleastrum
Candidastrum
Hymenanthes
Mumeazalea
Pentanthera (Azaleas)
Rhododendron
Therorhodion
Tsutsusi (Azaleas)

Source: RBG, Edinburgh Template:Taxobox end

Rhododendron (from the Greek: rhodos, "rose"; dendron, "tree") is a genus of flowering plants in the family Ericaceae. It is a large genus with over 600 species. They may be either evergreen or deciduous, and most have showy flower displays. It includes the plants known to gardeners as azalea.

The species are organised by subgenus, section, subsection and series. These can be basically divided into four groups:

Subgenus Rhododendron: small leaf or lepidotes (with scales on the underside of their leaves). Type: Rhododendron ferrugineum L.
Subgenus Hymenanthes: large leaf or elepidotes (without scales on the underside of their leaves). Type: Rhododendron degronianum Carr.
evergreen azaleas
deciduous azaleas.

Rhododendron is a very widely distributed genus, but a major concentration of diversity occurs in the Sino-Himalayan mountains of southeast Asia from central Nepal and Sikkim east to Yunnan and Sichuan, with other significant areas of diversity in the mountains of Indo-China, Korea, Japan and Taiwan. Several species also occur in North America and a few in Europe, and some tropical species occur as far south as Borneo and New Guinea.

Most species prefer acidic soil conditions. Some of the best known species are noted for their many clusters of large trumpet-shaped blooms and their glossy oval leaves. There are however alpine species with small flowers or with small leaves. Some species have leaves covered with scales or indentum.

The Rhododendron is the national flower of Nepal. It is also the state flower of the US states of Washington and West Virginia, and the state of Sikkim in India.

There are over 25,000 cultivars of Rhododendron. Most have been bred for their flowers, but a few are of garden interest because of ornamental leaves and some for ornamental stems.

Some species (e.g. Rhododendron ponticum in the United Kingdom) are invasive as introduced plants. Some species are poisonous to grazing animals. Some Rhododendrons have a toxin called grayanotoxin in their pollen and nectar. People have been known to become ill from eating honey made by bees feeding on rhododendron and azalea flowers.

Rhododendron species are used as food plants by the larvae of some Lepidoptera species including Copper Underwing, The Dun-bar, The Engrailed, The Gothic, Mottled Beauty, Scalloped Hazel, Svensson's Copper Underwing and Winter Moth.