Citizendia
Your Ad Here

For other uses, see Rhododendron (disambiguation).
Rhododendron
Rhododendron ponticum
Rhododendron ponticum
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Ericales
Family: Ericaceae
Genus: Rhododendron
L.
Subgenera

Source: RBG, Edinburgh

Rhododendron (from the Greek: rhodos, "rose", and dendron, "tree") is a genus of flowering plants in the family Ericaceae. Plants are living Organisms belonging to the kingdom Plantae. The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group Magnoliopsida is the Botanical name for a class of Flowering plants By definition the class will include the family Magnoliaceae, but its The Ericales are a large and diverse order of Dicotyledons including for example Tea, Persimmon, Blueberry, Brazil nut, and The Plant family Ericaceae (also called the heath family or ericaceous plants) are mostly lime -hating ( Calcifuge) Carl Linnaeus (Latinized as Carolus Linnaeus, also known after his ennoblement as, May 23 new style (13 May old style 1707 who laid the foundations for Rhododendron subgenus Hymenanthes is a subgenus of the genus Rhododendron, with a widespread distribution in the temperate Northern Rhododendron subgenus Pentanthera is a subgenus of the genus Rhododendron. Azaleas are flowering Shrubs making up part of the genus Rhododendron. Rhododendron subgenus Rhododendron is a subgenus of the genus Rhododendron. Azaleas are flowering Shrubs making up part of the genus Rhododendron. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly The Plant family Ericaceae (also called the heath family or ericaceous plants) are mostly lime -hating ( Calcifuge) It is a large genus with over 1000 species and most have showy flower displays. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. It includes the plants known to gardeners as azaleas. Azaleas are flowering Shrubs making up part of the genus Rhododendron.

The Rhododendron is a genus characterized by shrubs and small to (rarely) large trees, the smallest species growing to 10-20 cm tall, and the largest, R. A shrub or Bush is a horticultural rather than strictly botanical category of Woody plant, distinguished from a Tree A tree is a perennial Woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or arboreum, reported to 12 m tall. The leaves are spirally arranged; leaf size can range from 1-2 cm to over 50 cm, exceptionally 100 cm in R. In Botany, a leaf is an above-ground Plant organ specialized for Photosynthesis. sinogrande. They may be either evergreen or deciduous. In Botany, an Evergreen plant is a plant having leaves all year round Botany Autumn leaf color. See --> In Botany and Horticulture, deciduous Plants, including 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. An epiphyte is an organism that grows upon or attaches to a living plant

Contents

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. Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball' Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball' Australasia is a Region of Oceania: New Zealand, Australia, Papua New Guinea, and neighbouring Islands in the Pacific The highest species diversity is found in the Sino-Himalayan mountains 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. A mountain is a Landform that extends above the surrounding Terrain in a limited area with a peak Nepal (नेपाल) is a Landlocked country in South Asia. Sikkim ( Nepali:, also Sikhim) is a Landlocked Indian state nestled in the Himalayas It is the least populous state in India ( Postal map spelling: Szechwan and Szechuan) is a province in western China with its capital in Chengdu. Indochina, or the Indochinese Peninsula, is a region in Southeast Asia. Korea is a geographic area composed of two sovereign countries a civilization and a former state situated on the Korean Peninsula in East Asia. For a topic outline on this subject see List of basic Japan topics. Taiwan ( Taiwanese: Tâi-oân/Tāi-oân (historically 大灣/台員/大員/台圓/大圓/台窩灣 is an Island in East Asia. In addition, there are a significant number of tropical rhododendron species from southeast Asia to northern Australia, with 55 known species in Borneo and 164 in New Guinea. For a topic outline on this subject see List of basic Australia topics. Borneo is the third largest island in the world and is located at the centre of Maritime Southeast Asia. New Guinea, located just north of Australia, is the world's second largest island, having become separated from the Australian mainland when the area now known [1] Relatively fewer species occur in North America and Europe. Rhododendrons have not been found in South America or Africa.

Classification

Rhododendron wardii var. puralbum
Rhododendron wardii var. puralbum

The species are organized by subgenus, section, subsection and series. These are currently divided into four large and four small subgenera:

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. Ledum is a Genus name formerly widely recognised in the family Ericaceae, including 8 species of Evergreen Shrubs native Further realignment within the subgenera is currently proposed [2][3], 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. A cultivar is a cultivated Plant that has been selected and given a unique name because of its decorative or useful characteristics it is usually distinct from similar The Royal Horticultural Society ( RHS) was founded in 1804 in London, England as the Horticultural Society of London, and gained its present 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. Rhododendron ponticum, called Common Rhododendron or Pontic Rhododendron, is a species of Rhododendron native to southern The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located R. ponticum is difficult to eradicate, as its roots can make new shoots.

A garden with tall Rhododendrons in Lynnwood, Washington
A garden with tall Rhododendrons in Lynnwood, Washington
Sample species

A sample hybrid:

Toxicology

Some species are poisonous to grazing animals. Rhododendron atlanticum (Greek Ροδόδενδρο ( Dwarf azalea or Coastal azalea) is a species of Rhododendron native to Rhododendron canadense ( Rhodora) is a Deciduous flowering Shrub that is native to northeastern North America. Rhododendron catawbiense ( Catawba Rhododendron) is a species of Rhododendron native to the eastern United States, growing Rhododendron chapmanii, also known as Chapman's Rhododendron, is an evergreen shrub which is endemic to Florida. Rhododendron ferrugineum (sometimes called alpenrose, snow-rose, or rusty-leaved alpenrose) is an Evergreen Shrub Bog Labrador tea ( Rhododendron groenlandicum, formerly Ledum groenlandicum) is a Flowering plant in the subsection Ledum of Rhododendron lochiae is one of two recognised species of Rhododendron endemic to Australia. Rhododendron luteum ( Yellow Azalea or Honeysuckle Azalea) is a species of Rhododendron native to southeastern Europe Rhododendron macrophyllum ( Pacific Rhododendron, Coast Rhododendron or Big Leaf Rhododendron) is a broadleaf Evergreen Rhododendron maximum, also called Great Rhododendron, Great Laurel, Rose Bay, American Rhododendron or Big Rhododendron Rhododendron moulmainense ( Westland's Rhododendron; syn Rhododendron westladii Hemsl Rhododendron occidentale ( Western Azalea) is one of two Deciduous Rhododendron species native to western North America Rhododendron ponticum, called Common Rhododendron or Pontic Rhododendron, is a species of Rhododendron native to southern Rhododendron schlippenbachii ( Royal Azalea) is a species of Rhododendron native to the Korean Peninsula and adjacent regions Rhododendron spinuliferum is a species of Rhododendron native to Yunnan, S Sichuan, and Guizhou China. Marsh Labrador Tea, Northern Labrador Tea or Wild Rosemary ( Rhododendron tomentosum, formerly Ledum palustre) is a Flowering plant Rhododendron 'President Roosevelt' is a popular variegated Cultivar of Rhododendron with striking variegated leaves and trusses of bright red These Rhododendrons have a toxin called grayanotoxin in their pollen and nectar. A toxin ( Greek:, toxikon, lit (poison for use on arrows is a Poisonous substance produced by living cells or organisms that is active at very low Grayanotoxin is a Toxin found in Rhododendrons and other plants of the family Ericaceae. Pollen is a fine to coarse powder consisting of microgametophytes ( pollen grains) which produce the male Gametes (sperm cells of Nectar is a Sugar -rich liquid produced by plants It is produced either by the Flowers in which it attracts pollinating animals or by extrafloral People have been known to become ill from eating honey made by bees feeding on rhododendron and azalea flowers. Honey is a sweet and Viscous fluid produced by Honey bees (and some other species and derived from the nectar of Flowers According to the Bees are flying Insects closely related to Wasps and Ants Bees are a Monophyletic lineage within the superfamily Apoidea Xenophon described the odd behavior of Greek soldiers after having consumed honey in a village surrounded by rhododendrons. Xenophon (Ancient Greek, Modern Greek "Ξενοφών" "Ξενοφώντας" ca The Greeks ( Greek: Έλληνες) are a Nation and Ethnic group native to Greece, Cyprus and neighbouring regions Later, it was recognized that honey resulting from these plants have a slightly hallucinogenic and laxative effect. The general group of pharmacological agents commonly known as hallucinogens can be divided into three broad categories Psychedelics, Dissociatives Laxatives (or purgatives) are foods compounds or drugs taken to induce bowel movements or to loosen the stool most often taken to treat Constipation. The suspect rhododendrons are Rhododendron ponticum and Rhododendron luteum (formerly Azalea pontica), both found in northern Asia Minor. Rhododendron ponticum, called Common Rhododendron or Pontic Rhododendron, is a species of Rhododendron native to southern Rhododendron luteum ( Yellow Azalea or Honeysuckle Azalea) is a species of Rhododendron native to southeastern Europe Anatolia (Anadolu Ανατολία Anatolía) or Asia minor, comprising most of modern Turkey, is the geographic region bounded by the Black Eleven similar cases have been documented in Istanbul, Turkey during the 1980s [4]. Istanbul (historically Byzantium and later Constantinople; see the other Names of Istanbul) is the largest city of Turkey Turkey (Türkiye known officially as the Republic of Turkey ( is a Eurasian Country that stretches 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.

Use in landscaping

Both species and hybrid rhododendrons (including azaleas) are used extensively as ornamental plants in landscaping in many parts of the world, and many species and cultivars are grown commercially for the nursery trade. Ornamental plants are typically grown in the flower Garden or as House plants Most commonly they are grown for the display of their Flowers Other common Landscaping refers to any activity that modifies the visible features of an area of land including but not limited to living elements, such as A nursery is a place where Plants are propagated and grown to usable size Rhododendrons are often valued in landscaping for their structure, size, flowers, and the fact that many of them are evergreen [5]. Azaleas are frequently used around foundations and occasionally as hedges, and many larger-leafed rhododendrons lend themselves well to more informal plantings and woodland gardens, or as specimen plants. In some areas, larger rhododendrons can be pruned to encourage more tree-like form, with some species such as R. arboreum and R. Rhododendron arboreum, Lali Gurans the national flower of Nepal, is an evergreen shrub or small tree with a showy display of bright red flowers falconeri eventually growing to 10-15 m or more tall. [5]

Commercial growing

Rhododendrons are grown commercially in many areas for sale, and are occasionally collected in the wild, a practice now rare in most areas. Larger commercial growers often ship long distances; in the United States most of them are located on the west coast (Oregon, Washington and California). The United States of America —commonly referred to as the Oregon ( is a state in the Pacific Northwest region of the United States. Washington ( is a state in the Pacific Northwest region of the United States. California ( is a US state on the West Coast of the United States, along the Pacific Ocean. Large-scale commercial growing often selects for different characteristics than hobbyist growers might, such as resistance to root rot when over-watered, ability to be forced into budding early, ease of rooting or other propagation, and saleability. [6]

Planting and care

Like other ericaceous plants, most rhododendrons prefer acid soils with a pH of roughly 4. The Plant family Ericaceae (also called the heath family or ericaceous plants) are mostly lime -hating ( Calcifuge) 5-5. 5; some tropical Vireyas and a few other rhododendron species grow as epiphytes and require a planting mix similar to orchids. An epiphyte is an organism that grows upon or attaches to a living plant Rhododendrons have fibrous roots and prefer well-drained soils high in organic material. In areas with poorly-drained or alkaline soils, rhododendrons are often grown in raised beds using mediums such as composted pine bark. [7] Mulching and careful watering are important, especially before the plant is established.

Insects and diseases

Main article: List of rhododendron diseases

There are a number of insects that either target rhododendrons or will opportunistically attack them. This article is a list of diseases of Rhododendron ( Rhododendron spp Rhododendron borers and various weevils are major pests of rhododendrons, and many caterpillars will attack rhododendrons. Major diseases include Phytophthora root rot, stem and twig fungal dieback; Ohio State University Extension provides information on maintaining health of rhododendronsRhododendrons can easily be suffocated by other plants. Phytophthora (from Greek phytón “plant” and phthorá “destruction” “the plant-destroyer” is a Genus of plant-damaging Protists

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). A larva ( Latin; plural larvae) is a juvenile form of Animal with indirect development, undergoing Metamorphosis (for example Lepidoptera is an order of Insect that includes Moths and butterflies. A butterfly is an Insect of the order Lepidoptera. Like all Lepidoptera butterflies are notable for their unusual life cycle with a Rhododendron species are used as food plants by the Larvae of some species of the Order Lepidoptera, including Coleophoridae

Symbolism

Rhododendron ponticum is the national/state flower of Azad Jammu and Kashmir (Pakistan) and Indian Occupied Kashmir Rhododendron arboreum (Lali Gurans) is the national flower of Nepal. Rhododendron ponticum, called Common Rhododendron or Pontic Rhododendron, is a species of Rhododendron native to southern A state is a political association with effective Sovereignty over a geographic Area and representing a Population. The Azad State of Jammu and Kashmir, usually shortened to Azad Jammu and Kashmir ( AJK) or simply Azad Kashmir (literally "free Pakistan () officially the Islamic Republic of Pakistan, is a country located in South Asia, Southwest Asia, Middle East and ( Dogri: जम्मू और कश्मीर Urdu: جموں و کشمیر is the northernmost state of India. Rhododendron arboreum, Lali Gurans the national flower of Nepal, is an evergreen shrub or small tree with a showy display of bright red flowers Nepal (नेपाल) is a Landlocked country in South Asia. Rhododendron niveum is the state tree of Sikkim in India. Sikkim ( Nepali:, also Sikhim) is a Landlocked Indian state nestled in the Himalayas It is the least populous state in India India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country Rhododendron catawbiense, the predominant Rhododendron in the Appalachian Mountains, is the state flower of West Virginia, and is in the Flag of West Virginia. Rhododendron catawbiense ( Catawba Rhododendron) is a species of Rhododendron native to the eastern United States, growing The Appalachian Mountains ( often called the Appalachians, are a vast system of mountains in eastern North America. West Virginia ( is a state in the Appalachian Upland South, and Mid-Atlantic regions of the United States, bordered by The Flag of West Virginia consists of the State's coat of arms on a white field with a dark blue border Rhododendron macrophyllum, the predominant rhododendron on the Pacific Coast and in the Cascade Mountains is the state flower of Washington. Rhododendron macrophyllum ( Pacific Rhododendron, Coast Rhododendron or Big Leaf Rhododendron) is a broadleaf Evergreen Washington ( is a state in the Pacific Northwest region of the United States.

Gallery

Rhododendron decorum subsp. diaprepes

Wild Rhododendrons in Kashmir by Edward Molyneux; painted before 1908

Flowering Rhododendrons in Whitwick Leicestershire

Footnotes

  1. ^ Argent, G. Edward Molyneux (1891–1974 was a British Fashion designer whose fashion house was in operation from 1919 until 1950 Rhododendrons of subgenus Vireya. 2006. Royal Horticultural Society. ISBN 1-902896-61-0
  2. ^ Goetsch, L. A. , Eckert, A. J. & Hall, B. D. (2005). The molecular systematics of Rhododendron (Ericaceae): A Phylogeny based upon RPB2 gene sequences. Sys. Bot. 30(3): 616-626.
  3. ^ Summary of Goetsch-Eckert-Hall results
  4. ^ Nurhayat Sütlüpmar, Afife Mat and Yurdagül Satganoglu Poisoning by toxic honey in Turkey. Archives of Toxicology. Volume 67, Number 2, pages 148-150, February, 1993
  5. ^ a b Huxley, A. , ed. (1992). New RHS Dictionary of Gardening. Macmillan
  6. ^ Peter A. Cox (1993). The Cultivation of Rhododendrons. B. T. Batsford, London ISBN 0-7134-5630-2 (pp80-1)
  7. ^ Soil information for planting rhododendrons

References

See also

External links

Rhododendron Societies

This is a list of Plants which are Poisonous to Equines. Some may cause mild reactions such as Diarrhea, others can lead to serious problems including See Herbalism for the non-Chinese tradition of herbology Chinese Herbology ( is the common name for the subject of Chinese

Dictionary

rhododendron

-noun

  1. Any of various flowering shrubs in the genus Rhododendron.
© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
 Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic