The corollas are usually radially symmetrical ( actinomorphic ) but many flowers of the genus Rhododendron are somewhat bilaterally symmetrical ( zygomorphic ).

The genus Rhododendron was named by Linnaeus from the Greek word, itself derived from rhodos, rose, and dendron, tree.

Rhododendron ( from Ancient Greek ῥόδον " rose " and δένδρον " tree ") is a genus of over 1000 species of woody plants in the heath family, either evergreen or deciduous.

Rhododendron is a genus characterized by shrubs and small to ( rarely ) large trees, the smallest species growing to tall, and the largest, R. giganteum, reported to over tall.

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.

Species of the genus Rhododendron are native to every continent of the world, except South America and Africa.

Azaleas () are flowering shrubs comprising two of the eight subgenera of the genus Rhododendron, Tsutsuji ( evergreen ) and Pentanthera ( deciduous ).

These are evergreen shrubs that belong to the genus Rhododendron.

The flowers are unusual in comparison with other species of the genus Rhododendron found in northeastern North America.

* Rhododendron and Azalea-1, 857 recorded specimens of the genus Rhododendron ( which includes azaleas ), representing 649 unique names ( taxa ).

Recent genetic evidence has shown that the species previously treated in this genus are correctly placed in the genus Rhododendron, where they are now treated as Rhododendron subsect.

Because some of the species names used in Ledum could not be used in Rhododendron ( the names already having been used for other species already in this large genus ), new names had to be coined for them.

* Subgenus Rhododendron L .: small leaf or lepidotes ( with scales on the underside of their leaves ); several hundred species, type: Rhododendron ferrugineum.

Rhododendron is extremely toxic to horses, with some animals dying within a few hours of ingesting the plant, although most horses tend to avoid it if they have access to good forage.

* Historical Survey of Rhododendron Collecting-With Emphasis on its Close Associations with Horticulture

Rhododendron ' President Roosevelt ' is a popular cultivar of Rhododendron with striking variegated leaves and trusses of bright red flowers that fade to white in the centre.

In California and parts of Oregon, it is also associated with hardwoods, including Tanoak, Madrone, Rhododendron, Salal, and Manzanita.

It is speculated that the seed was spread with Rhododendron stock.

The flowers are white, pink or purple, in corymbs of 10-50, reminiscent of Rhododendron flowers but flatter, with a star-like calyx of five conjoined petals ; each flower is 1 – 3 cm diameter.

The other major habitat type in the ecoregion is the shola-grassland complex, found at elevations of 1, 900 to 2, 220 m. Shola is a stunted forest, with an upper story of small trees, generally Pygeum gardneri, Schefflera racemosa, Linociera ramiflora, Syzygium spp., Rhododendron nilgiricum, Mahonia nepalensis, Elaeocarpus recurvatus, Ilex denticulata, Michelia nilagirica, Actinodaphne bourdellonii, and Litsea wightiana.

), with rhododendron ( Rhododendron fastigiatum ) abundant in the understory.

Some common forest types in this region include Castanopsis tribuloides mixed with Schima wallichi, Rhododendron spp., Lyonia ovalifolia, Eurya acuminata, and Quercus glauca ; Castanopsis-Laurales forest with Symplocas spp.

Semicarpus anacardium, Rhododendron arboreum and Lyoma ovalifolia ; Schima-Lagestromea parviflora forest, Quercus lamellosa forest with Quercus lenata and ' Quercus glauca ; Castanopsis forests with Castanopsis hystrix and Lauraceae.

Associations of Lauraceous species are common in broadleaved forests ; for example, Litsea spp., Litsea cupola, Persea odoratissima, Persea duthiei, etc., along with such others as Engelhardtia spicata, Rhododendron arboreum, Lyonia ovalifolia, Pyrus pashia, Rhus spp., Acer oblongum, Myrica esculenta, Michelia kisopa, and Betula alnoides.

The common forest types of this zone include Rhododendron arboreum, Rhododendron barbatum, Lyonia spp., Pieris formosa ; Tsuga dumosa forest with such deciduous species as Acer and Magnolia ; deciduous mixed broadleaved forest of Acer campbellii, Acer pectinatum, Sorbus cuspidata, and Magnolia campbellii ; mixed broadleaved forest of Rhododendron arboreum, Acer campbellii, Symplocos ramosissima and Lauraceae.

Rhododendron and mountain laurel thickets interspersed with sourgum, dogwood and large oaks, hickories, hemlocks and maples shade the trail.

* Hutberg ( 294 m )-mountain with park, with Rhododendron

The Caucasian Grouse is a sedentary species, breeding in the Caucasus and Pontic Mountains of northeast Turkey on open slopes with low Rhododendron or other scrubs but in proximity to deciduous broad-leaf forest.

* The Helen S. Layer Rhododendron Garden contains heaths and vernal witch-hazels in March, through to the fall heathers and native witch-hazels in October and November, with over 1, 200 rhododendron plants and over 100 mountain laurel plants.

Rhododendron borers and various weevils are major pests of rhododendrons, and many caterpillars will attack them.

Throughout the year such festivals as North Carolina Mineral and Gem Festival and North Carolina Rhododendron Festival bring many people to the area.

They are tended by the volunteers of The Blue Mountains Rhododendron Society of NSW, many of whom live in the town.

This zone is habitat for many other important tree and large shrub species such as Abies pindrow, Betula utilis, Buxus rugulosa, Benthamidia capitata, Corylus ferox, Deutzia staminea, Euonymus tingens, Abies spectalbilis, Acanthopanax cissifolius, Acer campbellii, Acer pectinatum, Betula alnoides, Coriaria terminalis, Fraxinus macrantha, Dodecadenia grandiflora, Eurya cerasifolia, Hydrangea heteromala, Ilex dipyrena, Ligustrum spp., Litsea elongata, Juglans regia, Lichelia doltsopa, Myrsine capitallata, Neolitsea umbrosa, Philadelphus tomentosus, Osmanthus fragrans, Prunus cornuta, Rhododendron companulatum, Sorbus cuspidate, and Viburnum continifolium.

The Arboretum currently contains 50 species of conifers, and many species of oak, maple, rowan, hawthorn, Rhododendron, Kalmia, and wildflowers.

* McDonald Azalea and Rhododendron Garden ( 1995 )-more than 500 individual azaleas and rhododendrons of many varieties.

* Asian-has an outstanding Rhododendron collection ( 259 taxa, 397 accessions ) including many mature tree Rhododendrons too tender for most North American climates.

Trees include the deciduous Oak and Maple, and evergreens like Pine, and various types of Rhododendron.

Henry Compton was ordained Bishop of London in 1675 ; he imported several new plant species to the gardens at Fulham Palace and first cultivated some flora found in Britain today, including the American magnolia, M. virginiana, Liriodendron, Liquidambar and the first American azalea grown in England, Rhododendron viscosum.

* A portion of the Gardens has several species of Rhododendron and hybrids with several associated plants of Hostas, Helleborus and Liliums.

* Subgenus Hymenanthes ( Blume ) K. Koch: large leaf or elepidotes ( without scales on the underside of their leaves ); about 140 species, type: Rhododendron degronianum.

* Subgenus Pentanthera G. Don: deciduous azaleas ; about 25 species, type Rhododendron luteum.

* Subgenus Tsutsusi: evergreen azaleas, about 110 species ; type Rhododendron indicum.

: five species ; type Rhododendron ovatum.

* Subgenus Candidastrum ( Sleumer ) Philipson & Philipson: one species ; Rhododendron albiflorum.

* Subgenus Mumeazalea: one species, Rhododendron semibarbatum.

* Subgenus Therorhodion: one species, Rhododendron camtschaticum.

Some species ( e. g. Rhododendron ponticum in Ireland and the United Kingdom ) are invasive as introduced plants, spreading in woodland areas replacing the natural understory.

Rhododendron species are used as food plants by the larvae of some members of the order Lepidoptera ( butterflies and moths ) ( See List of Lepidoptera that feed on rhododendrons ).

Other Impatiens species, such as I. auricoma, Garden Balsam ( I. balsamina ), Blue Diamond Impatiens ( I. namchabarwensis ), Parrot Flower ( I. psittacina ), Congo Cockatoo ( I. niamniamensis ), Ceylon Balsam ( I. repens ) or Poor Man's Rhododendron ( I. sodenii ) are also often seen as ornamental plants.

Rhododendron atlanticum ( Greek Ροδόδενδρο ) ( Dwarf azalea or Coastal azalea ), is a species of Rhododendron native to coastal areas of the eastern United States, from New Jersey south to Georgia.

This garden grows over 10 Azalea species including Red Azalea ( Rhododendron simsii ), Lovely Azalea ( Rhododendron pulchrum ), Purple Azalea ( Rhododendron pulchrum var.

There are also rare species such as Yellow Azalea ( Rhododendron x molle ) and Westland's Rhododendron ( Rhododendron moulmainense ).

P. ramorum also infects a great number of other plant species, significantly woody ornamentals such as Rhododendron, Viburnum, and Pieris, causing foliar symptoms known as ramorum dieback or ramorum blight.