Overview

Distribution

Localities documented in Tropicos sources

Rhododendron L.:
United States (North America)
Colombia (South America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.
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Localities documented in Tropicos sources

Ledum L.:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO 63110 USA

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Ecology

Associations

In Great Britain and/or Ireland:
Foodplant / saprobe
colony of Acrodontium dematiaceous anamorph of Acrodontium hydnicola is saprobic on dead Rhododendron

Foodplant / gall
Agrobacterium tumefaciens causes gall of stem (base, esp.) of Rhododendron

Foodplant / pathogen
Armillaria mellea s.l. infects and damages Rhododendron

Foodplant / saprobe
hypostromatic hysterothecia of Aulographum hederae is saprobic on dead leaf of Rhododendron
Remarks: season: 1-7

Foodplant / saprobe
effuse colony of Belemnospora dematiaceous anamorph of Belemnospora epiphylla is saprobic on dead leaf of Rhododendron

Foodplant / saprobe
effuse colony of Belemnospora dematiaceous anamorph of Belemnospora verruculosa is saprobic on dead twig of Rhododendron

Foodplant / saprobe
effuse colony of Alysidium anamorph of Botryobasidium candicans is saprobic on rotten wood of Rhododendron
Remarks: season: 1-12

Foodplant / saprobe
effuse colony of Acladium anamorph of Botryobasidium conspersum is saprobic on dead bark of Rhododendron

Foodplant / spot causer
immersed pseudothecium of Botryosphaeria rhodorae causes spots on newly dead leaf of Rhododendron
Remarks: season: 2-9

Foodplant / saprobe
effuse colony of Brachysporium dematiaceous anamorph of Brachysporium dingleyae is saprobic on dead, rotten wood of Rhododendron
Remarks: season: 4-9

Foodplant / saprobe
fruitbody of Calocera pallidospathulata is saprobic on decayed wood of Rhododendron
Remarks: season: 1-12

Foodplant / saprobe
solitary or in small groups, erumpent bcoming more or less superficial ascocarp of Capronia pleiospora is saprobic on rotten wood of Rhododendron

Plant / epiphyte
epiphyllous thallus of Cephaleuros grows on live leaf of Rhododendron

Foodplant / saprobe
amphigenous, erumpent perithecium of Chaetapiospora rhododendri is saprobic on dead leaf of Rhododendron
Remarks: season: 2-4

Plant / epiphyte
seta-bearing mycelial mat of Chaetothyrium babingtonii grows on leaf of Rhododendron

Foodplant / pathogen
basidiome of Chondrostereum purpureum infects and damages stem of Rhododendron

Foodplant / parasite
mostly hypophyllous telium of Chrysomyxa ledi var. rhododendri parasitises live leaf of Rhododendron

Foodplant / saprobe
immersed, numerous, gregarious pycnidium of Coleophoma coelomycetous anamorph of Coleophoma cylindrospora is saprobic on dead leaf of Rhododendron

Foodplant / saprobe
fruitbody of Crepidotus applanatus var. applanatus is saprobic on decayed log of Rhododendron

Foodplant / saprobe
scattered, immersed, plurilocular stroma of Cytospora coelomycetous anamorph of Cytospora subclypeata is saprobic on dead, locally dark reddish-brown, shining branch of Rhododendron
Remarks: season: 2-11

Foodplant / saprobe
effuse colony of Haplographium dematiaceous anamorph of Dematioscypha dematiicola is saprobic on dead branch of Rhododendron
Remarks: season: 1-12

Foodplant / saprobe
synnema of Graphium dematiacous anamorph of Dendrostilbella smaragdina is saprobic on dead wood of Rhododendron
Remarks: season: 3-8

Foodplant / sap sucker
Dialeurodes chittendeni sucks sap of live leaf of Rhododendron
Remarks: season: esp. 6-7

Foodplant / saprobe
perithecium of Diaporthe eres is saprobic on wood of Rhododendron

Foodplant / feeds on
pycnidium of Diplodina coelomycetous anamorph of Diplodina eurhododendri feeds on Rhododendron

Foodplant / parasite
cleistothecium of Erysiphe azaleae parasitises live leaf of Rhododendron

Foodplant / gall
fruitbody of Exobasidium japonicum causes gall of live leaf of Rhododendron

Foodplant / spot causer
concentrically arranged acervulus of Gloeosporium coelomycetous anamorph of Glomerella cingulata causes spots on live leaf of Rhododendron

Foodplant / saprobe
hysterothecium of Gloniopsis praelonga is saprobic on dead twig of Rhododendron
Remarks: season: 1-12

Foodplant / sap sucker
Graphocephala fennahi sucks sap of live leaf of Rhododendron

Foodplant / saprobe
effuse colony of Helminthosporium dematiaceous anamorph of Helminthosporium velutinum is saprobic on fallen, dead branch of Rhododendron

Foodplant / saprobe
effuse colony of Henicospora dematiaceous anamorph of Henicospora minor is saprobic on dead leaf of Rhododendron
Remarks: season: 9-11

Foodplant / saprobe
apothecium of Hyaloscypha leuconica is saprobic on dead wood of Rhododendron
Remarks: season: 1-12
Other: minor host/prey

Foodplant / saprobe
hysterothecium of Hysterium angustatum is saprobic on dead, decorticate branch of Rhododendron
Remarks: season: 3-5

Foodplant / sap sucker
adult of Kleidocerys resedae sucks sap of live Rhododendron
Other: minor host/prey

Foodplant / saprobe
opening by slit pseudothecium of Lembosina aulographoides is saprobic on attached twig (bark) of Rhododendron
Remarks: season: 2-6

Foodplant / saprobe
immersed apothecium of Lophodermium vagulum is saprobic on dead, fallen leaf of Rhododendron

Foodplant / saprobe
effuse colony of Mariannaea anamorph of Mariannaea elegans is saprobic on bark of Rhododendron

Plant / nest
female of Megachile builds nest using semicircular or oblong pieces of live leaf of Rhododendron

Foodplant / saprobe
superficial, often in very large clusters pseudothecium of Melanomma pulvis-pyrius is saprobic on dry, hard, decorticate branch wood of Rhododendron
Remarks: season: 9-5

Foodplant / saprobe
colony of Gonytrichum dematiaceous anamorph of Melanopsammella inaequalis is saprobic on fallen, dead branch of Rhododendron
Remarks: season: 1-12

Foodplant / saprobe
sessile apothecium of Mollisia cinerea is saprobic on dead wood of Rhododendron
Remarks: season: 1-12

Foodplant / spot causer
acervulus of Monochaetia coelomycetous anamorph of Monochaetia karstenii causes spots on live leaf of Rhododendron

Foodplant / saprobe
sporodochium of Tubercularia anamorph of Nectria cinnabarina is saprobic on dead branch of Rhododendron

Foodplant / mycorrhiza / endomycorrhiza
mycelium of Oidiodendron maius is endomycorrhizal with live root of Rhododendron

Foodplant / open feeder
caterpillar of Orgyia antiqua grazes on live leaf of Rhododendron
Remarks: season: -7/8

Foodplant / feeds on
adult of Otiorhynchus singularis feeds on live Rhododendron

Foodplant / open feeder
nocturnal adult of Otiorhynchus sulcatus grazes on leaf (margin) of Rhododendron
Other: major host/prey

Foodplant / saprobe
stromatic, single or in groups of 2-3 apothecium of Ovulinia azaleae is saprobic on Rhododendron
Remarks: Other: uncertain

Foodplant / saprobe
acervulus of Pestalotiopsis coelomycetous anamorph of Pestalotiopsis funerea is saprobic on dead Rhododendron

Foodplant / spot causer
amphigenous acervulus of Pestalotiopsis coelomycetous anamorph of Pestalotiopsis guepinii causes spots on dead leaf of Rhododendron
Remarks: season: 10-11

Foodplant / saprobe
acervulus of Pestalotiopsis coelomycetous anamorph of Pestalotiopsis sydowiana is saprobic on dead Rhododendron

Foodplant / saprobe
acervulus of Pestalotiopsis coelomycetous anamorph of Pestalotiopsis versicolor is saprobic on dead Rhododendron

Foodplant / saprobe
thinly scattered, mostly hypophyllous, dimorphic pycnidium of Ceuthospora coelomycetous anamorph of Phacidium falconeri is saprobic on fallen, long dead leaf of Rhododendron
Remarks: season: 6-10

Foodplant / saprobe
colony of Phaeostalagmus dematiaceous anamorph of Phaeostalagmus cyclosporus is saprobic on fallen, dead branch of Rhododendron
Remarks: season: 1-12

Foodplant / saprobe
colony of Phaeostalagmus dematiaceous anamorph of Phaeostalagmus tenuissimus is saprobic on litter of Rhododendron

Foodplant / feeds on
pycnidium of Phoma coelomycetous anamorph of Phoma leveillei feeds on Rhododendron

Foodplant / feeds on
pycnidium of Phoma coelomycetous anamorph of Phoma pomorum feeds on Rhododendron

Foodplant / feeds on
pycnidium of Phoma coelomycetous anamorph of Phoma rhodorae feeds on Rhododendron

Foodplant / saprobe
epiphyllous, immersed, in swarm perithecium of Phomatospora gelatinospora is saprobic on dead, attached leaf of Rhododendron
Remarks: season: 4-5

Foodplant / feeds on
pycnidium of Phyllosticta coelomycetous anamorph of Phyllosticta cunninghami feeds on Rhododendron

Foodplant / spot causer
Phyllosticta coelomycetous anamorph of Phyllosticta rhododendri causes spots on live leaf of Rhododendron

Foodplant / spot causer
epiphyllous pycnidium of Phyllosticta coelomycetous anamorph of Phyllosticta rhododendri sensu Westd. causes spots on leaf of Rhododendron
Remarks: season: 5-12

Foodplant / spot causer
epiphyllous, scattered, immersed then erumpent pycnidium of Phyllosticta coelomycetous anamorph of Phyllosticta saccardoi causes spots on fading leaf of Rhododendron
Remarks: season: 8

Foodplant / false gall
mycelium of Phytophthora ramorum causes swelling of cankered twig of Rhododendron
Other: major host/prey

Foodplant / saprobe
superficial, subiculate pseudothecium of Protoventuria arxii is saprobic on dead twig of Rhododendron
Remarks: season: 5

Foodplant / saprobe
caespitose fruitbody of Psathyrella piluliformis is saprobic on dead, decayed trunk (large) of Rhododendron
Other: unusual host/prey

Foodplant / spot causer
amphigenous colony of Pseudocercospora dematiaceous anamorph of Pseudocercospora handelii causes spots on live leaf of Rhododendron

Foodplant / sap sucker
hypophyllous Pulvinaria floccifera sucks sap of live leaf of Rhododendron

Foodplant / pathogen
coremium of Pycnostysanus dematiacous anamorph of Pycnostysanus azaleae infects and damages leaf of Rhododendron
Other: sole host/prey

Foodplant / feeds on
Rhopalomesites tardyi feeds on dead wood of Rhododendron

Foodplant / saprobe
colony of Geniculosporium dematiaceous anamorph of Rosellinia aquila is saprobic on dead branch of Rhododendron
Remarks: season: 2-5

Foodplant / saprobe
fruitbody of Scytinostroma ochroleucum is saprobic on dead, decayed wood of Rhododendron
Other: unusual host/prey

Foodplant / saprobe
acervulus of Seimatosporium coelomycetous anamorph of Seimatosporium arbuti is saprobic on dead leaf of Rhododendron

Foodplant / saprobe
acervulus of Seimatosporium coelomycetous anamorph of Seimatosporium mariae is saprobic on dead leaf of Rhododendron

Foodplant / pathogen
amphigenous, immersed pycnidium of Septoria coelomycetous anamorph of Septoria azaleae infects and damages live leaf of Rhododendron
Remarks: season: 3-9

Foodplant / saprobe
effuse colony of Sporidesmium dematiaceous anamorph of Sporidesmium bombacis is saprobic on dead leaf of Rhododendron
Remarks: season: 5

Foodplant / saprobe
effuse colony of Sporidesmium dematiaceous anamorph of Sporidesmium leptosporum is saprobic on dead branch of Rhododendron
Remarks: season: 1-12

Foodplant / sap sucker
nymph of Stephanitis rhododendri sucks sap of Rhododendron

Foodplant / sap sucker
Stephanitis takeyai sucks sap of Rhododendron

Foodplant / saprobe
extensively subiculate apothecium of Tapesia fusca is saprobic on dead, fallen branch of Rhododendron
Remarks: season: 1-12
Other: minor host/prey

Foodplant / saprobe
effuse colony of Triposporium dematiaceous anamorph of Triposporium elegans is saprobic on dead, often grey or purple stained twig of Rhododendron
Remarks: season: 1-12

Foodplant / saprobe
Tubulicrinis regificus is saprobic on dead branch of Rhododendron

Foodplant / saprobe
effuse colony of Veronaea dematiaceous anamorph of Veronaea botryosa is saprobic on wood of Rhododendron

Foodplant / internal feeder
caterpillar of Zeuzera pyrina feeds within live bud of Rhododendron

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:827Public Records:514
Specimens with Sequences:816Public Species:247
Specimens with Barcodes:796Public BINs:0
Species:265         
Species With Barcodes:261         
          
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Barcode data

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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Rhododendron

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Wikipedia

Rhododendron

Rhododendron (from Ancient Greek ῥόδον rhódon "rose" and δένδρον déndron "tree")[2][3] is a genus of over 1,000 species of woody plants in the heath family, either evergreen or deciduous. Most species have showy flowers.

Azaleas make up two subgenera of Rhododendron. They are distinguished from "true" rhododendrons by having only five anthers per flower.

Description[edit]

Rhododendron is a genus characterised by shrubs and small to (rarely) large trees, the smallest species growing to 10–100 cm (3.9–39.4 in) tall, and the largest, R. protistum var. giganteum, reported to 30 m (98 ft) tall.[4][5] The leaves are spirally arranged; leaf size can range from 1–2 cm (0.39–0.79 in) to over 50 cm (20 in), exceptionally 100 cm (39 in) in R. sinogrande. They may be either evergreen or deciduous. In some species, the undersides 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 section Vireya that often grow as epiphytes. Species in this genus may be part of the heath complex in oak-heath forests in eastern North America.[6][7]

Taxonomy[edit]

Rhododendron wardii var. puralbum
A garden with tall Rhododendrons in Lynnwood, Washington

The species are organized by subgenus, section, subsection and series.

Subgenera[edit]

There are four large and four small subgenera:

Species[edit]

See the List of Rhododendron species for a complete list of accepted species. Selected species include:

Hybrids[edit]

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 hybrids have fragrant flowers[8]—such as the Loderi hybrids, created by crossing R. fortunei and R. griffithianum.[9]

Reclassification[edit]

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,[10][11] including the merging of subgenus Hymenanthes into subgenus Pentanthera.

Ecology[edit]

Distribution[edit]

Species of the genus Rhododendron are native to Asia, North America, Europe and Australia. The highest species diversity is found in the Himalayas from Uttarakhand, Nepal and Sikkim to Yunnan and Sichuan, with other significant areas of diversity in the mountains of Korea, Japan and Taiwan.

Tropical rhododendron species range from southeast Asia to northern Australia, with 55 known species in Borneo and 164 in New Guinea. Interestingly,[why?] the species in New Guinea are native to subalpine moist grasslands at around 3,000 metres above sea level in the Central Highlands.[12] Relatively fewer species occur in North America and Europe.

Invasive species[edit]

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. R. ponticum is difficult to eradicate, as its roots can make new shoots.

Insects[edit]

A number of insects either target rhododendrons or will opportunistically attack them. Rhododendron borers and various weevils are major pests of rhododendrons, and many caterpillars will preferentially devour them.

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).

Diseases[edit]

Major diseases include Phytophthora root rot, stem and twig fungal dieback; Ohio State University Extension provides information on maintaining health of rhododendrons.[13] Rhododendrons can easily be suffocated by other plants.

Cultivation[edit]

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. Rhododendrons are often valued in landscaping for their structure, size, flowers, and the fact that many of them are evergreen.[14] 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. falconeri eventually growing to 10–15 m or more tall.[14]

Commercial growing[edit]

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 state and California). Large-scale commercial growing often selects for different characteristics that hobbyist growers might want, such as resistance to root rot when overwatered, ability to be forced into budding early, ease of rooting or other propagation, and saleability.[15] In the Indian state of Himachal Pradesh, rhododendron flowers have been used for some time to make popular fruit and flower wines. The industry is promoted by the state government with tax benefits, looking to promote this industry as a full-fledged subclass of its economy.[16]

Horticultural divisions[edit]

Horticulturally, rhododendrons may be divided into the following groups:-[17]

  • Evergreen rhododendrons: the main default category
  • Vireya (Malesian) rhododendrons: epiphytic tender shrubs[18]
  • Azaleas (section of generally small-sized, small-leaved and small-flowered shrubs):
    • Deciduous hybrid azaleas:[19]
      • Ghent (Gandavense) hybrids - Belgian raised[20]
      • Knap Hill-Exbury hybrids - English raised[21]
      • Mollis hybrids - Dutch & Belgian raised[22]
      • New Zealand Ilam hybrids - derived from Knap Hill/Exbury hybrids
      • Occidentale hybrids - English raised
      • Rustica hybrids - sweet-scented, double-flowered
    • Evergreen hybrid azaleas:
      • Gable hybrids - raised by Joseph B. Gable in Pennsylvania, USA[23]
      • Glenn Dale hybrids - USA raised complex hybrids
      • Indian (Indica) hybrids - mostly of Belgian origin
      • Kaempferi hybrids - Dutch raised
      • Kurume hybrids - Japanese raised
      • Kyushu hybrids - very hardy Japanese azaleas (to -30°C)
      • Oldhamii hybrids - dwarf hybrids raised at Exbury, England
      • Satsuki hybrids - Japanese raised, originally for bonsai
      • Shammarello hybrids - raised in Northern Ohio, USA[24]
      • Vuyk (Vuykiana) hybrids - raised in the Netherlands[25]
  • Azaleodendrons - semi-evergreen hybrids between deciduous azaleas and rhododendrons

Planting and care[edit]

Nova Zembla Rhododendrons growing in a nursery in New Jersey.

Like other ericaceous plants, most rhododendrons prefer acid soils with a pH of roughly 4.5-5.5; some tropical Vireyas and a few other rhododendron species grow as epiphytes and require a planting mix similar to orchids. 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 media such as composted pine bark.[26] Mulching and careful watering are important, especially before the plant is established.

A new calcium-tolerant stock of rhododendrons (patented as 'Inkarho') has been exhibited at the RHS Chelsea Flower Show in London (2011). Individual hybrids of rhododendrons have been grafted on to a rootstock on a single rhododendron plant that was found growing in a chalk quarry. The rootstock is able to grow in calcium-rich soil up to a pH of 7.5.[27][28]

Active substances[edit]

Toxicology[edit]

Some species of rhododendron are poisonous to grazing animals because of 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. Xenophon described the odd behaviour of Greek soldiers after having consumed honey in a village surrounded by Rhododendron ponticum during the march of the Ten Thousand in 401 BC. Pompey's soldiers reportedly suffered lethal casualties following the consumption of honey made from Rhododendron deliberately left behind by Pontic forces in 67 BC during the Third Mithridatic War. Later, it was recognized that honey resulting from these plants has a slightly hallucinogenic and laxative effect.[29] The suspect rhododendrons are Rhododendron ponticum and Rhododendron luteum (formerly Azalea pontica), both found in northern Asia Minor. Eleven similar cases have been documented in Istanbul, Turkey during the 1980s.[30] 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. The effects of R. ponticum was mentioned in the 2009 film Sherlock Holmes as a proposed way to arrange a fake execution.[31] It was also mentioned in the third episode of Season 2 of BBC's Sherlock (TV series), and has been speculated to have been a part of Sherlock's fake death scheme.

Additional pharmacology[edit]

Animal studies and in vitro research has identified possible anti-inflammatory and hepatoprotective activities which may be due to the antioxidant effects of flavonoids or other phenolic compounds and saponins the plant contains.[32][33][34] Xiong et al. have found that the root of the plant is able to reduce the activity of NF-κB in rats.[35]

Culture[edit]

Symbolism[edit]

Rhododendron arboreum (lali guransh) is the national flower of Nepal. R. ponticum is the state flower of Indian-administered Kashmir and Pakistan-controlled Kashmir. Rhododendron niveum is the state tree of Sikkim in India. Rhododendron is also the state tree of the state of Uttarakhand, India.

Rhododendron maximum, the most widespread rhododendron of the Appalachian Mountains, is the state flower of West Virginia, and is in the Flag of West Virginia. Rhododendron macrophyllum, a widespread rhododendron of the Pacific Northwest, is the state flower of Washington.

Literature[edit]

In Joyce's Ulysses, rhododendrons play an important role in Leopold and Molly's early courtship: Molly remembers them in her soliloquy - "the sun shines for you he said the day we were lying among the rhododendrons on Howth head in the grey tweed suit and his straw hat the day I got him to propose to me". Jasper Fforde a British author, also uses rhododendron as a motif throughout many of his published books. See Thursday Next series,[36] and Shades of Grey.[37]

Culinary[edit]

The rhododendron is the national flower of Nepal, where the flower is considered edible and enjoyed for its sour taste. The pickled flower can last for months and the flower juice is also marketed. The flower, fresh or dried, is added to fish curry in the belief that it will soften the bones. The juice of rhododendron flower is used to make a squash called burans(named after the flower)in the hilly regions of Uttarakhand. It is admired for its distinctive flavor and color.[citation needed]

See also[edit]

Footnotes[edit]

  1. ^ "RBG, Edinburgh". Rbge.org.uk. Retrieved 2013-02-26. 
  2. ^ Harper, Douglas. "rhododendron". Online Etymology Dictionary. 
  3. ^ ῥόδον, δένδρον. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
  4. ^ [1], Big Tree Rhododendron
  5. ^ [2] Rhododendron protistum var. giganteum
  6. ^ The Natural Communities of Virginia Classification of Ecological Community Groups (Version 2.5), Virginia Department of Conservation and Recreation, 2012
  7. ^ Schafale, M. P. and A. S. Weakley. 1990. Classification of the natural communities of North Carolina: third approximation. North Carolina Natural Heritage Program, North Carolina Division of Parks and Recreation.
  8. ^ http://plants.wildeel.com/rhodofrag.html
  9. ^ Davidian, H.H., "Rhododendron Species, Vol. II: Elepidotes, Part 1 Arboreum-Lacteum" Timber Press, Inc., Portland, Oregon, plate 44 & 45
  10. ^ 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. doi:10.1600/0363644054782170. 
  11. ^ http://www.flounder.ca/FraserSouth/Goetsch-Eckert-Hall.asp
  12. ^ Argent, G. Rhododendrons of subgenus Vireya. 2006. Royal Horticultural Society. ISBN 1-902896-61-0
  13. ^ "AG.ohio-state.edu". AG.ohio-state.edu. Retrieved 2013-02-26. 
  14. ^ a b Huxley, A., ed. (1992). New RHS Dictionary of Gardening. Macmillan
  15. ^ Peter A. Cox (1993). The Cultivation of Rhododendrons. B. T. Batsford, London ISBN 0-7134-5630-2 (pp80-1)
  16. ^ The-fuga-experience.com[dead link]
  17. ^ RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 1405332964. 
  18. ^ "Vireya Rhododendrons - Welcome". Vireya.net. Retrieved 2013-02-26. 
  19. ^ "Deciduous Azaleas". Rhodyman.net. Retrieved 2013-02-26. 
  20. ^ "JARS v38n3 - Rescuing the Ghent and Rustica Flore Pleno Azaleas". Scholar.lib.vt.edu. 2012-04-03. Retrieved 2013-02-26. 
  21. ^ "Don Hyatt's Knap Hill Azalea Page". Tjhsst.edu. Retrieved 2013-02-26. 
  22. ^ "Quarterly Bulletin of the ARS - Vol 14 No 1, Living, Mollis Azaleas". Scholar.lib.vt.edu. 1960-01-01. Retrieved 2013-02-26. 
  23. ^ "The Rhododendron Legacy of Joe Gable". Tjhsst.edu. Retrieved 2013-02-26. 
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References[edit]

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Ledum

Ledum is a genus name formerly widely recognised in the family Ericaceae, including 8 species of evergreen shrubs native to cool temperate and subarctic regions of the Northern Hemisphere and commonly known as Labrador Tea.

Taxonomy[edit]

Reclassification into Rhododendron[edit]

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. Ledum.

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.

Species[edit]

The species formerly listed in Ledum, with their current accepted names in Rhododendron, are:

Hybrids[edit]

One natural hybrid also occurs:

Uses[edit]

Ledum (L. groenlandicum) essential oil in clear glass vial

Some species (e.g. L. groenlandicum) have been used to produce Labrador Tea. Other species have varying levels of toxicity (e.g. L. glandulosum). Evergreen Labrador Tea grows slowly, but retains its leaves year-round. Users should take care not to over-harvest leaves from any single plant.

Ledum sp. often grows together with poisonous plants such as Bog-laurel and Bog-rosemary, but certain species (e.g. L. groenlandicum and L. palustre) are easily distinguished by the distinctive rust coloured fuzz on the bottom of leaves.

According to a Russian study from 1991,[citation needed] Ledum was able to almost completely inactivate the tick-borne bacterial infection caused by Borrelia, involved in the pathogenesis of Lyme Disease.

References[edit]

1. Kron, Kathleen A. & Judd, Walter S. (1990) Phylogenetic Relationships within the Rhodoreae (Ericaceae) with Specific Comments on the Placement of Ledum Systematic Botany (1990), 1S(1): pp. S7-68

2. Harmaja, Harri (1990) New names and nomenclatural combinations in Rhododendron (Ericaceae) Ann. Bot. Fennici 27:203-204

3. Harmaja, Harri (1991) Taxonomic notes on Rhododendron subsection Ledum (Ledum, Ericaceae), with a key to its species. Ann. Bot. Fennici 28: 171-173.

4. Harmaja, Harri (1999) Rhododendron diversipilosum, comb. nov. (Ericaceae). Ann. Bot. Fennici 35: 263-264

5. Harmaja, Harri (2002) Rhododendron subulatum, comb. nova (Ericaceae). Ann. Bot. Fennici 39: 183-184

6. Kihlman, Bengt A. (2004) Hybrids Between Ledums and Lepidote Rhododendrons. Journal of the American Rhododendron Society 58(2):74-81

7. Fokina, GI. Vopr Virusol, (1991) Experimental phytotherapy of tick-borne encephalitis,

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Rhododendron subg. Rhododendron

A species of the Vireya section.

Rhododendron subgenus Rhododendron is a subgenus of the genus Rhododendron.

The subgenus includes three sections:

  • Rhododendron sect. Pogonathum (six species; Himalaya and adjacent mountains)
  • Rhododendron sect. Rhododendron (about 120 species in 25 subsections; temperate to subarctic Northern Hemisphere)
  • Rhododendron sect. Vireya (about 300 species; tropical southeast Asia, Australasia) – sometimes split off as a ninth subgenus.

References


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