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{{short description|Genus of flowering plants in the heath family Ericaceae}}{{Other uses}}{{Use dmy dates|date=January 2020}}{{Automatic taxobox| image = Alpenroos.jpg| image_caption = Rhododendron ferrugineum! style="background:#ccf" |Genus ||style="background:#ccf" |Subgenus ||style="background:#ccf" |Section ||style="border-right:solid black 2px; background:#ccf" |Species ||style="background:#ccf" |Subgenus ||style="background:#ccf" |Section

52

Ypresian - presentDILLHOFF

LAST2=LEOPOLD

LAST3=MANCHESTER

YEAR=2005

JOURNAL=CANADIAN JOURNAL OF EARTH SCIENCES

ISSUE=2

DOI=10.1139/E04-084

URL=HTTP://WWW.FOSSILMUSEUM.NET/FOSSIL_SITES/MCABEE/MCABEEFOSSILS.PDF

ARCHIVE-DATE=2022-10-09, live, | display_parents = 2| taxon = Rhododendron

Carl Linnaeus>L.HTTPS://WWW.BIODIVERSITYLIBRARY.ORG/ITEM/13829#PAGE/404/MODE/1UP >LAST=LINNAEUS

AUTHOR-LINK=CARL LINNAEUS

VOLUME=TOMUS I

PAGE=392

PUBLISHER=LAURENTII SALVII

ACCESS-DATE=15 JUNE 2014, | type_species = Rhododendron ferrugineum

Carl Linnaeus>L.

Goetsch

Hall

ref=Goetsch}} | subdivision = Azaleastrum Choniastrum Hymenanthes Rhododendron Therorhodion Former subgenera: Candidastrum Mumeazalea Pentanthera Tsutsusi

RHODODENDRON L. >AUTHOR=

WEBSITE=PLANTS OF THE WORLD ONLINE

ACCESS-DATE=16 SEPTEMBER 2020,

Anthodendron Rchb. Azaleastrum Rydb. × Azaleodendron Rodigas Biltia Small Candollea Baumg. Chamaecistus Regel Chamaerhododendron Bubani Chamaerhododendros Duhamel Diplarche Hook.f. & Thomson Dulia Adans. Haustrum Noronha Hochenwartia Crantz Hymenanthes Blume Iposues Raf. × Ledodendron F.de Vos Ledum Ruppius ex L. Loiseleria Rchb. Menziesia Sm. Osmothamnus DC. Plinthocroma Dulac × Rhodazalea Anon. Rhodora L. Rhodothamnus Lindl. & Paxton Stemotis Raf. Theis Salisb. ex DC. Therorhodion Small Tsusiophyllum Maxim. Vireya Blume Waldemaria Klotzsch }}}}Rhododendron ({{IPAc-en|ËŒ|r|oÊŠ|d|É™|ˈ|d|É›|n|d|r|É™n}}; {{plural form}}: rhododendra) is a very large genus of about 1,024 species of woody plants in the heath family (Ericaceae). They can be either evergreen or deciduous. Most species are native to eastern Asia and the Himalayan region, but smaller numbers occur elsewhere in Asia, and in North America, Europe and Australia.JOURNAL, Shrestha N, etal, 2018, Global patterns of Rhododendron diversity: The role of evolutionary time and diversification rates, Global Ecology & Biogeography, 27, 8, 913–924, 10.1111/geb.12750, 92383323, free, 2018GloEB..27..913S, 10852/67628, free, It is the national flower of Nepal, the state flower of Washington and West Virginia in the United States, the state flower of Nagaland and Himachal Pradesh in India, the provincial flower of Jiangxi in China and the state tree of Sikkim and Uttarakhand in India. Most species have brightly colored flowers which bloom from late winter through to early summer.BOOK, Botanica: The Illustrated A-Z of Over 10,000 Garden Plants and How to Cultivate Them, Turner, R.J. Jr., amp, Wasson, Ernie, 1997, 742, Azaleas make up two subgenera of Rhododendron. They are distinguished from "true" rhododendrons by having only five anthers per flower. Etymology The common and generic name comes {{etymology|grc|{{wikt-lang|grc|ῥόδον}} {{grc-transl|ῥόδον}}|rose||{{wikt-lang|grc|δένδρον}} {{grc-transl|δένδρον}}|tree}}.{{OEtymD|rhododendron}}{{LSJ|r(odo/dendron|ῥοδόδενδρον}}, {{LSJ|r(o/don|ῥόδον}}, {{LSJ|de/ndron|δένδρον|ref}}.DICTIONARY, rhododendron, An etymological dictionary of modern English, 1234,weblink Weekley, Ernest, 1921, London J. Murray, Description File:Найкращі миті життя.jpg|thumb|Rhododendron in the Carpathian MountainsCarpathian MountainsRhododendron is a genus of shrubs and small to (rarely) large trees, the smallest species growing to {{convert|10|-|100|cm|abbr=on|sigfig=1|round=each}} tall, and the largest, R. protistum var. giganteum, reported to {{convert|30|m|abbr=on|sigfig=1}} tall.WEB,weblink Big Tree Rhododendron, Global Trees Campaign, WEB,weblink Rhododendron protistum var. giganteum, Colombel, Marc, The leaves are spirally arranged; leaf size can range from {{convert|1|-|2|cm|abbr=on|sigfig=1}} to over {{convert|50|cm|abbr=on|sigfig=1}}, exceptionally {{convert|100|cm|abbr=on|sigfig=1}} 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. A recently discovered species in New Guinea has flowers up to six inches (fifteen centimeters) in width,NEWS, Hotz, Robert Lee, February 7, 2006, A Trove of Unearthly Species....etc, Los Angeles Times, A8, and see: JOURNAL,weblink 2006-04-01, Finding a Lost World, Charles Q. Choi, Scientific American, 294, 4, 32, 10.1038/scientificamerican0406-32d, 2006SciAm.294d..32C, the largest in the whole genus. The accompanying photograph shows it as having seven petals. 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.WEB,weblink Introduction, www.dcr.virginia.gov, 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.They have frequently been divided based on the presence or absence of scales on the abaxial (lower) leaf surface (lepidote or elepidote). These scales, unique to subgenus Rhododendron, are modified hairs consisting of a polygonal scale attached by a stalk.{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}}Rhododendron are characterised by having inflorescences with scarious (dry) perulae, a chromosome number of x=13, fruit that has a septicidal capsule, an ovary that is superior (or nearly so), stamens that have no appendages, and agglutinate (clumped) pollen.{{sfnp|Brown |Craven |Udovicic |Ladiges |2006 |ref=Brown2006}} Taxonomy File:Ghorepani,_Tadapani,_as_well_as_Mulde_Hill.jpg|thumb|Rhododendrons (Guras) at Ghorepani, Nepal ]]File:Manaslu-Circuit Rhododendron Forest.jpg|thumb|right|Rhododendron forest in NepalNepalFile:Rhododendron＆Vast ocean of clouds、コバノミツバツツジ＆篠山盆地雲海、盃ヶ岳4256293.JPG|thumb|right|Rhododendron in JapanJapanFile:Garden with Rhododendrons.JPG|thumb|right|A garden with tall Rhododendrons in Lynnwood, WashingtonLynnwood, WashingtonFile:Rhododendron (গুরাস)02.jpg|thumb|Rhododendron (গুরাস), Sandakphu, West Bengal, India ]](File:Azalea -- Rhododendron.jpg|thumb|Azalea, Texas Gulf Coast)File:Azalea as a Bonsai (5155648449).jpg|thumb|BonsaiBonsaiRhododendron is the largest genus in the family Ericaceae, with over 1000 species, WEB, Rhododendrons: Wakehurst's hidden treasure. Rhododendron facts,weblink Royal Botanic Gardens Kew, Board of Trustees of the Royal Botanic Gardens, Kew, 21 May 2022, WEB,weblink Sorting out the Genus Rhododendron: A Taxonomic Overview of this Large Complex of Species, University of California Botanical Garden at Berkeley,weblink" title="web.archive.org/web/20140714150332weblink">weblink 14 July 2014, (though estimates vary from 850 to 1200{{sfnp|Fayaz |2012 |page=3 |ref=Fayaz}}WEB, Rhododendron Species Conservation Group,weblink Rhododendron Species Conservation Group, The Rhododendron Species Conservation Group, 21 May 2022, ) and is morphologically diverse. Consequently, the taxonomy has been historically complex.{{sfnp|Brown |Craven |Udovicic |Ladiges |2006 |ref=Brown2006}} Early history Although Rhododendrons had been known since the description of Rhododendron hirsutum by Charles de l'Écluse (Clusius) in the sixteenth century, and were known to classical writers (Magor 1990), and referred to as Chamaerhododendron (low-growing rose tree), the genus was first formally described by Linnaeus in his Species Plantarum in 1753.BOOK, Linnaeus, C., Carl Linnaeus, Genera Plantarum, 5th, 185, 1754,weblink Laurentii Salvii, Stockholm, 1 October 2017, He listed five species under Rhododendron (Rhododendron ferrugineum (type species), R. dauricum, R. hirsutum, R. chamaecistus (now Rhodothamnus chamaecistus (L.) Rchb.) and R. maximum). At that time he considered the then known six species of AzaleaBOOK,weblink Linnaeus, C., Carl Linnaeus, Species Plantarum, Azalea, Tomus I, 150, 1753, Laurentii Salvii, Stockholm, 15 June 2014, that he had described earlier in 1735 in his Systema Naturae as a separate genus.WEB, Andrews, Charles,weblink American Rhododendron Society (Azalea Chapter), What is an Azalea?, JOURNAL,weblink Herbert A., Spady, GROPING FOR GROUPING: Rhododendron Taxonomy, The Quarterly Bulletin of the American Rhododendron Society, 35, 4, Fall 1981, Linnaeus' six species of Azalea were Azalea indica, A. pontica, A. lutea, A. viscosa, A. lapponica and A. procumbens (now Kalmia procumbens), which he distinguished from Rhododendron by having five stamens, as opposed to ten. As new species of what are now considered Rhododendron were discovered, they were assigned to separate genera if they seemed to differ significantly from the type species. For instance Rhodora (Linnaeus 1763) for Rhododendron canadense, Vireya (Blume 1826)WEB,weblink Chris, Callard, The History of Vireya Rhododendron Culture, vireya.net, 1998–2015, 28 September 2017, and Hymenanthes (Blume 1826) for Rhododendron metternichii, now R. degronianum. Meanwhile, other botanists such as Salisbury (1796)BOOK,weblink Salisbury, R.A., Richard Anthony Salisbury, Prodromus Stirpium in horto ad Chapel Allerton, 1796, 286, London, la, and Tate (1831)BOOK,weblink Economic history: Farm-gardening and market gardening, A History of the County of Middlesex: Volume 12, Chelsea, Patricia E C Croot, London, 2004, 150–155, British History Online, began to question the distinction between Azalea and Rhododendron, and finally in 1836, Azalea was incorporated into Rhododendron and the genus divided into eight sections. Of these Tsutsutsi (Tsutsusi), Pentanthera, Pogonanthum, Ponticum and Rhodora are still used, the other sections being Lepipherum, Booram, and Chamaecistus. This structure largely survived till recently (2004), following which the development of molecular phylogeny led to major re-examinations of traditional morphological classifications, although other authors such as Candolle, who described six sections,{{sfnp|Candolle |1838 |ref=Candolle}} used slightly different numeration.Soon, as more species became available in the nineteenth century so did a better understanding of the characteristics necessary for the major divisions. Chief amongst these were Maximovicz's Rhododendreae Asiae Orientali and Planchon. Maximovicz used flower bud position and its relationship with leaf buds to create eight "Sections".{{sfnp|JIN |DING |ZHANG |HONG |2010 |ref=JDZH}} Bentham and Hooker used a similar scheme, but called the divisions "Series". It was not until 1893 that Koehne appreciated the significance of scaling and hence the separation of lepidote and elepidote species. The large number of species that were available by the early twentieth century prompted a new approach when Balfour introduced the concept of grouping species into series. The Species of RhododendronBOOK, Stevenson, J.B., The Species of Rhododendron, The Rhododendron Society, Edinburgh, 1930, referred to this series concept as the Balfourian system. That system continued up to modern times in Davidian's four volume The Rhododendron Species.{{sfnp|Davidian |ref=Davidian}} Modern era The next major attempt at classification was by Sleumer who from 1934 began incorporating the Balfourian series into the older hierarchical structure of subgenera and sections, according to the International Code of Botanical Nomenclature, culminating in 1949 with his "Ein System der Gattung Rhododendron L.",JOURNAL, Sleumer, H, 1949, Ein System der Gattung Rhododendron L., Bot. Jahrb. Syst., 74, 511–553, and subsequent refinements. Most of the Balfourian series are represented by Sleumer as subsections, though some appear as sections or even subgenera. Sleumer based his system on the relationship of the flower buds to the leaf buds, habitat, flower structure, and whether the leaves were lepidote or non-lepidote. While Sleumer's work was widely accepted, many in the United States and the United Kingdom continued to use the simpler Balfourian system of the Edinburgh group.Sleumer's system underwent many revisions by others, predominantly the Edinburgh group in their continuing Royal Botanic Garden Edinburgh notes. Cullen of the Edinburgh group, placing more emphasis on the lepidote characteristics of the leaves, united all of the lepidote species into subgenus Rhododendron, including four of Sleumer's subgenera (Rhododendron, Pseudoazalea, Pseudorhodorastrum, Rhodorastrum).JOURNAL, J., Cullen, A revision of Rhododendron I. Subgenus Rhododendron sections Rhododendron and Pogonanthum, Notes from the Royal Botanic Garden Edinburgh, 39, 1, 1980, 0080-4274, In 1986 Philipson & Philipson raised two sections of subgenus Aleastrum (Mumeazalea, Candidastrum) to subgenera, while reducing genus Therorhodion to a subgenus of Rhododendron.JOURNAL, Philipson, W.R., Philipson, M.N., 1986, A revision of Rhododendron III. Subgenera Azaleastrum, Mumeazalea, Candidastrum and Therorhodion, Notes from the Royal Botanic Garden Edinburgh, 44, 1–23, 0080-4274, In 1987 Spethmann, adding phytochemical features proposed a system with fifteen subgenera grouped into three 'chorus' subgenera.JOURNAL, Spethmann, W, 1987, A new infrageneric classification and phylogenetic trends in the genus Rhododendron (Ericaceae), Plant Systematics and Evolution, 157, 1–2, 9–31, 1615-6110, 10.1007/BF00939178, 1987PSyEv.157....9S, 35751500, A number of closely related genera had been included together with Rhododendron in a former tribe, Rhodoreae. These have been progressively incorporated into Rhododendron.JOURNAL, Stevens, PF, 1971, A classification of the Ericaceae: subfamilies and tribes, Botanical Journal of the Linnean Society, 64, 1, 1–53, 10.1111/j.1095-8339.1971.tb02133.x, Chamberlain and Rae moved the monotypic section Tsusiopsis together with the monotypic genus Tsusiophyllum into section Tsutsusi,{{sfnp|Chamberlain |Rae |1990 |ref=ChamRae1990}} while Kron & Judd reduced genus Ledum to a subsection of section Rhododendron.JOURNAL, Kron, K. A., Judd, W. S., 1990, Phylogenetic relationships within the Rhodoreae (Ericaceae) with specific comments on the placement of Ledum, Systematic Botany, 15, 1, 57–68, 10.2307/2419016, 2419016, Then Judd & Kron moved two species (Rhododendron schlippenbachii, R. quinquefolium) from section Brachybachii, subgenus Tsutsusi and two from section Rhodora, subgenus Pentanthera (R. albrechtii, R. pentaphyllum) into section Sciadorhodion, subgenus Pentanthera.JOURNAL, Judd, W. S., Kron, K. A., 1995, A revision of Rhododendron. VI. Subgenus Pentanthera (sections Sciadorhodion, Rhodora, and Viscidula), Edinburgh Journal of Botany, 52, 1, 1–54, 10.1017/s0960428600001906, free, Finally Chamberlain brought the various systems together in 1996, with 1,025 species divided into eight subgenera. For a comparison of the Sleumer and Chamberlain schemata see Table 1 of Goetsch (2005).{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}}{{sfnp|Brown |Craven |Udovicic |Ladiges |2006 |ref=Brown2006}}{{sfnp|Cullen |2005 |ref=Cullen2005}} Phylogenetic analyses {hide}cladogram |align=left |title= {{anchor|Clad1{edih}Cladogram of genus Rhododendron (Goetsch et al. 2005) |cladogram={{clade |style=400px; |label1=  |1={{clade |label1=  |1={{clade |label1=  |1={{clade |label1= {{sc|A}}  |1={{clade |1=Rhododendron |2=Choniastrum }} |label2= {{sc|B}}  |2=Hymenanthes }} |label2= {{sc|C}}  |2=Azaleastrum }} |2={{clade |label1=  |1=Therorhodion }} }} }} }}The era of molecular analysis rather than descriptive features can be dated to the work of Kurashige (1988) and Kron (1997) who used matK sequencing. Later Gao et al. (2002) used ITS sequences to determine a cladistic analysis. They confirmed that the genus Rhododendron was monophyletic, with subgenus Therorhodion in the basal position, consistent with the matK studies. Following publication of the studies of Goetsch et al. (2005) with RPB2,{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}} there began an ongoing realignment of species and groups within the genus, based on evolutionary relationships. Their work was more supportive of Sleumer's original system than the later modifications introduced by Chamberlain et al..{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}}WEB, Goetsch, Loretta A., Eckert, Andrew J., Hall, Benjamin D., 2005,weblinkweblink" title="web.archive.org/web/20130227185832weblink">weblink 27 February 2013, Fraser South Rhododendron Society, Excerpts from and comments on a paper published by: Loretta Goetsch, Andrew Eckert and Benjamin Hall, University of Washington, 2005 Annual ARS ConventionThe major finding of Goetsch and colleagues was that all species examined (except R. camtschaticum, subgenus Therorhodion) formed three major clades which they labelled {{sc|A}}, {{sc|B}}, and {{sc|C}}, with the subgenera Rhododendron and Hymenanthes as monophyletic groups nested within clades {{sc|A}} and {{sc|B}}, respectively. By contrast subgenera Azaleastrum and Pentanthera were polyphyletic, while R. camtschaticum appeared as a sister to all other rhododendrons. The small polyphyletic subgenera Pentanthera and Azaleastrum were divided between two clades. The four sections of Pentanthera between clades {{sc|B}} and {{sc|C}}, with two each, while Azaleastrum had one section in each of {{sc|A}} and {{sc|C}}.Thus subgenera Azaleastrum and Pentanthera needed to be disassembled, and Rhododendron, Hymenanthes and Tsutsusi correspondingly expanded. In addition to the two separate genera included under Rhododendron by Chamberlain (Ledum, Tsusiophyllum), Goetsch et al.. added Menziesia (clade {{sc|C}}). Despite a degree of paraphyly, the subgenus Rhododendron was otherwise untouched with regard to its three sections but four other subgenera were eliminated and one new subgenus created, leaving a total of five subgenera in all, from eight in Chamberlain's scheme. The discontinued subgenera are Pentanthera, Tsutsusi, Candidastrum and Mumeazalea, while a new subgenus was created by elevating subgenus Azaleastrum section Choniastrum to subgenus rank.Subgenus Pentanthera (deciduous azaleas) with its four sections was dismembered by eliminating two sections and redistributing the other two between the existing subgenera in clades {{sc|B}} (Hymenanthes) and {{sc|C}} (Azaleastrum), although the name was retained in section Pentanthera (14 species) which was moved to subgenus Hymenanthes. Of the remaining three sections, monotypic Viscidula was discontinued by moving Rhododendron nipponicum to Tsutsusi ({{sc|C}}), while Rhodora (2 species) was itself polyphyletic and was broken up by moving Rhododendron canadense to section Pentanthera ({{sc|B}}) and Rhododendron vaseyi to section Sciadorhodion, which then became a new section of subgenus Azaleastrum ({{sc|C}}).Subgenus Tsutsusi ({{sc|C}}) was reduced to section status retaining the name, and included in subgenus Azaleastrum. Of the three minor subgenera, all in {{sc|C}}, two were discontinued. The single species of monotypic subgenus Candidastrum (Rhododendron albiflorum) was moved to subgenus Azaleastrum, section Sciadorhodion. Similarly the single species in monotypic subgenus Mumeazalea (Rhododendron semibarbatum) was placed in the new section Tsutsusi, subgenus Azaleastrum. Genus Menziesa (9 species) was also added to section Sciadorhodion. The remaining small subgenus Therorhodion with its two species was left intact. Thus two subgenera, Hymenanthes and Azaleastrum were expanded at the expense of four subgenera that were eliminated, although Azaleastrum lost one section (Choniastrum) as a new subgenus, since it was a distinct subclade in {{sc|A}}. In all, Hymenanthes increased from one to two sections, while Azaleastrum, by losing one section and gaining two increased from two to three sections.{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}} (See schemata under Subgenera) (Table 1.){| class="wikitable" style="width:500px;"|+ Table 1.: Taxonomic changes within genus Rhododendron! style="border-right:solid black 2px; background: #ccf" colspan=4|Chamberlain (1996)||style="background: #ccf" colspan=2|Goetsch (2005)

Menziesa >

9 species

style="text-align:center;" rowspan=4

Azaleastrum{{sc>C}}

rowspan=4|Sciadorhodion

Rhododendron

Candidastrum

style="border-right:solid black 2px"|R. albiflorum

Pentanthera

Sciadorhodion

style="border-right:solid black 2px"| 4 species

Rhodora

style="border-right:solid black 2px"|R. vaseyi

R. canadense

style="text-align:center;" rowspan=2

Hymenanthes{{sc>B}}

rowspan=2|Pentanthera

Pentanthera >

14 species

Viscidula >

R. nipponicum

style="text-align:center;" rowspan=4

Azaleastrum{{sc>C}}

rowspan=4|Tsutsusi

Tsutsusi

Brachycalyx

style="border-right:solid black 2px"| 15 species

Tsutsusi >

65 species

Mumeazalea >

R. semibarbatum

Azaleastrum >

Choniastrum >

11 species

style="text-align:center;"

Choniastrum{{sc>A}}

Subsequent research has supported the revision by Goetsch, although has largely concentrated on further defining the phylogeny within the subdivisions.{{sfnp|Craven |Goetsch |Hall |Brown |2008 |ref=Craven2008}} In 2011 the two species of Diplarche were also added to Rhododendron, incertae sedis.{{sfnp|Craven|2011 |ref=Craven2011}}

Subdivision

This genus has been progressively subdivided into a hierarchy of subgenus, section, subsection, and species.

Subgenera

Terminology from the Sleumer (1949) system is frequently found in older literature, with five subgenera and is as follows;

• Subgenus Lepidorrhodium Koehne: Lepidotes. 3 sections
• Subgenus Eurhododendron Maxim.: Elipidotes.
• Subgenus Pseudanthodendron Sleumer: Deciduous azaleas. 3 sections
• Subgenus Anthodendron Rehder & Wilson: Evergreen azaleas. 3 sections
• Subgenus Azaleastrum Planch.: 4 sections

In the later traditional classification, attributed to Chamberlain (1996), and as used by horticulturalists and the American Rhododendron Society,{{sfnp|Genus Rhododendron Taxonomic Tree |ref=ARS2}} Rhododendron has eight subgenera based on morphology, namely the presence of scales (lepidote), deciduousness of leaves, and the floral and vegetative branching patterns, after Sleumer (1980).{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}}{{sfnp|Brown |Craven |Udovicic |Ladiges |2006 |ref=Brown2006}} These consist of four large and four small subgenera. The first two subgenera (Rhododendron and Hymenanthes) represent the species commonly considered as 'Rhododendrons'. The next two smaller subgenera (Pentanthera and Tsutsusi) represent the 'Azaleas'. The remaining four subgenera contain very few species. The largest of these is subgenus Rhododendron, containing nearly half of all known species and all of the lepidote species.

• Subgenus Rhododendron {{small|L.}}: Small leaf or lepidotes (scales on the underside of the leaves). 3 sections, 462 species, type species: Rhododendron ferrugineum.
• Subgenus Hymenanthes {{small|(Blume) K.Koch}}: Large leaf or elepidotes (without scales). 1 section, 224 species, type Rhododendron degronianum.
• Subgenus Pentanthera {{small|(G. Don) Pojarkova}}: Deciduous azaleas. 4 sections, 23 species, type Rhododendron luteum.
• Subgenus Tsutsusi {{small|(Sweet) Pojarkova}}: Evergreen azaleas. 2 sections, 80 species, type Rhododendron indicum.
• Subgenus Azaleastrum {{small|Planch.}}: 2 sections, 16 species, type Rhododendron ovatum.
• Subgenus Candidastrum {{small|Franch.}}: 1 species, Rhododendron albiflorum.
• Subgenus Mumeazalea {{small|(Sleumer) W.R. Philipson & M.N. Philipson}}: 1 species, Rhododendron semibarbatum.
• Subgenus Therorhodion {{small|(Maxim.) A. Gray}}: 2 species (Rhododendron camtschaticum, Rhododendron redowskianun).

For a comparison of the Sleumer and Chamberlain systems, see Goetsch et al. (2005) Table 1.{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}}This division was based on a number of what were thought to be key morphological characteristics. These included the position of the inflorescence buds (terminal or lateral), whether lepidote or elepidote, deciduousness of leaves, and whether new foliage was derived from axils from previous year's shoots or the lowest scaly leaves (Table 2.).(File:Rhododendron luteum BotGardBln1105Autumn.JPG|thumb|right|Deciduous Rhododendron luteum in fall color)(File:Rhododendron kaempferi 08.jpg|thumb|Evergreen azalea Rhododendron kaempferi)(File:2014-10-29 13 26 34 Evergreen Rhododendron foliage coloring before being shed in Ewing, New Jersey.JPG|thumb|right|Evergreen azalea cultivar leaf color before shedding)File:Rhododendron after freezing rain.jpg|thumb|right|Rhododendron after freezing rainfreezing rain{| class="wikitable"|+ Table 2.: Morphological classification of Rhododendron (Chamberlain 1996)! style="background:#ccf" |Inflorescence buds !!style="background:#ccf" |Leaf scales !!style="background:#ccf" |Leaf shoots !!style="border-right:solid black 2px; background:#ccf" |Leaves !!style="background:#ccf" |Subgenus !!style="background:#ccf" |Section Terminal colspan=3RhododendronAbsentrowspan=4EvergreenHymenanthesDeciduousrowspan=3Rhododendron subg. Pentanthera>Pentanthera Pentanthera| Rhodora| ViscidulaLowest leaves style="border-left:solid black 2px"Pentanthera>|SciadorhodionTsutsusiLateral style="border-right:solid black 2px"Rhododendron subg. Azaleastrum>AzaleastrumDeciduousCandidastrum| Mumeazalea|TherorhodionFollowing the cladistic analysis of Goetsch et al. (2005){{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}} this scheme was simplified, based on the discovery of three major clades (A, B, C) as follows.Clade A

• Subgenus Rhododendron {{Small|L.}}: Small leaf or lepidotes (scales on the underside of the leaves). 3 sections, about 400 species, type species: Rhododendron ferrugineum.
• Subgenus Choniastrum {{Small|Franch.}}: 11 species

Clade B

• Subgenus Hymenanthes {{Small|(Blume) K.Koch}}: Large leaf or elepidotes (without scales), including deciduous azaleas. 2 sections, about 140–225 species, type Rhododendron degronianum.

Clade C

• Subgenus Azaleastrum {{Small|Planch.}}: Evergreen azaleas. 3 sections, about 120 species, type Rhododendron ovatum.

Sister taxon

• Subgenus Therorhodion {{Small|(Maxim.) A. Gray}}: 2 species (Rhododendron camtschaticum, Rhododendron redowskianun).

Sections and subsections

The larger subgenera are further subdivided into sections and subsectionsWEB,weblink Concerning the Origin and Distribution of Rhododendrons, Irving, E., R. Hebda, 1993, Journal of the American Rhododendron Society, American Rhododendron Society, 4 November 2012, Some subgenera contain only a single section, and some sections only a single subsection. Shown here is the traditional classification, with species number after Chamberlain (1996), but this scheme is undergoing constant revision. Revisions by Goetsch et al. (2005){{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}} and by Craven et al. (2008){{sfnp|Craven |Goetsch |Hall |Brown |2008 |ref=Craven2008}} shown in (parenthetical italics). Older ranks such as Series (groups of species) are no longer used but may be found in the literature, but the American Rhododendron Society still uses a similar device, called Alliances{{sfnp|Genus Rhododendron Taxonomic Tree |ref=ARS2}}

• Subgenus Rhododendron L. (3 sections, 462 species: increased to five sections in 2008)
  • (Discovereya (Sleumer) Argent, raised from Vireya)
  • Pogonathum Aitch. & Hemsl. (13 species; Himalaya and adjacent mountains)
  • (Pseudovireya (C.B.Clarke) Argent, raised from Vireya)
  • Rhododendron L. (149 species in 25 subsections; temperate to subarctic Northern Hemisphere)
  • Vireya (Blume) Copel.f. (300 species in 2 subsections; tropical southeast Asia, Australasia. At one time considered separate subgenus{{sfnp|Argent|2006 |ref=Argent2006}})
• Subgenus Hymenanthes (Blume) K.Koch (1 section, 224 species) (Increased to two sections)
  • Ponticum {{small|G. Don}} (24 subsections)
  • (Pentanthera {{small|(G. Don) Pojarkova}} (2 subsections – new section, moved from subgenus Pentanthera)
• Subgenus Pentanthera {{small|(G. Don) Pojarkova}} (4 sections, 23 species) (Discontinued)
  • Pentanthera {{small|(G. Don) Pojarkova}} (2 subsections – moved to subgenus Hymenanthes)
  • Rhodora (L.) G. Don (2 species; Rhododendron canadense, Rhododendron vaseyi) (Discontinued, redistributed)
  • Sciadorhodion Rehder & Wilson (4 species) (Moved to subgenus Azaleastrum)
  • Viscidula Matsum. & Nakai (1 species; Rhododendron nipponicum) (Discontinued, added to section Tsutsusi, subgenus Azaleastrum)
• Subgenus Tsutsusi (Sweet) Pojarkova (2 sections, 80 species) (Discontinued, reduced to section and moved to subgenus Azaleastrum)
  • Brachycalyx Sweet (3 alliances, 15 species)
  • Tsutsusi (Sweet) Pojarkova (65 species)
• Subgenus Azaleastrum Planch. (2 sections, 16 species) (Increased to three sections)
  • Azaleastrum Planch. (5 species)
  • (Choniastrum Franch. (11 species) (Raised to subgenus))
  • (Sciadorhodion Rehder & Wilson (4 species) (Moved from subgenus Pentanthera))
  • (Tsutsusi (Sweet) Pojarkova (reduced from subgenus))
• Subgenus Candidastrum Franch. (1 species: Rhododendron albiflorum) (Discontinued, moved to section Sciadorhodion, subgenus Azaleastrum)
• Subgenus Mumeazalea (Sleumer) W.R. Philipson & M.N. Philipson (1 species: Rhododendron semibarbatum) (Discontinued, moved to section Tsutsusi, subgenus Azaleastrum)
• Subgenus Therorhodion A. Gray (2 species)
• (Subgenus Choniastrum Franch. (11 species))

The system used by the World Flora Online {{As of|2023|December|lc=yes}} uses six subgenera, four of which are divided further:WEB, WFO, December 2023, Rhododendron L.., World Flora Online,weblink 2024-02-22,

• subgenus Azaleastrum {{small|Planch. ex K.Koch}}WEB, WFO, December 2023, Rhododendron subg. Azaleastrum Planch. ex K.Koch, World Flora Online,weblink 2024-02-22,
  • section Azaleastrum {{small|Planch. ex Maxim.}}
  • section Sciadorhodion {{small|Rehder & E.H.Wilson}}
  • section Tsutsutsi {{small|(Sweet) Pojark.}}
• subgenus Choniastrum {{small|Franch.}}
• subgenus Hymenanthes {{small|(Blume) K.Koch}}WEB, WFO, December 2023, Rhododendron subg. Hymenanthes (Blume) K.Koch, World Flora Online,weblink 2024-02-22,
  • section Pentanthera {{small|G.Don}}
  • section Ponticum {{small|G.Don}}
  • section Rhodora {{small|(L.) G.Don}}
• subgenus Rhododendron {{small|L.}}WEB, WFO, December 2023, Rhododendron subg. Rhododendron L.., World Flora Online,weblink 2024-02-22,
  • section Pogonanthum {{small|G.Don}}
  • section Rhododendron {{small|}}
• subgenus Therorhodion {{small|(Maxim) Rehder}}
• subgenus Vireya {{small|Clarke}}WEB, WFO, December 2023, Rhododendron subg. Vireya L.., World Flora Online,weblink 2024-02-22,
  • section Albovireya {{small|(Sleumer) Argent}}
  • section Discovireya {{small|(Sleumer) Argent}}
  • section Hadranthe {{small|Schltr.}}
  • section Malayovireya {{small|(Sleumer) Argent}}
  • section Pseudovireya {{small|(Clarke) Sleumer}}
  • section Schistanthe {{small|Schltr.}}
  • section Siphonovireya {{small|Argent}}

Species

{{further|List of Rhododendron species}}

Distribution and habitat

File:Rhododendron fallacinum (cropped).jpg|thumb|upright|left|Rhododendron fallacinum photographed in situ on Mount Kinabalu, BorneoBorneoSpecies of the genus Rhododendron are widely distributed between latitudes 80°N and 20°S and are native to areas from North America to Europe, Russia, and Asia, and from Greenland to Queensland, Australia and the Solomon Islands.{{sfnp|Brown |Craven |Udovicic |Ladiges |2006 |ref=Brown2006}} The centres of diversity are in the Himalayas and Maritime Southeast Asia,JOURNAL, GAO Lian-Ming, LI De-Zhu, ZHANG Chang-Qin, YANG Jun-Bo, 2002, Infrageneric and Sectional Relationships in the Genus Rhododendron (Ericaceae) Inferred from ITS Sequence Data,weblink Am Botanica Sinica, 44, 11, 1351–1356, with the greatest species diversity in the Sino-Himalayan region, Southwest China and northern Burma, from India – Himachal Pradesh, Uttarakhand, Sikkim and Nagaland to Nepal, northwestern Yunnan and western Sichuan and southeastern Tibet. Other significant areas of diversity are in the mountains of Korea, Japan and Taiwan. More than 90% of Rhododendron sensu Chamberlain belong to the Asian subgenera Rhododendron, Hymenanthes and section Tsutsusi. Of the first two of these, the species are predominantly found in the area of the Himalayas and Southwest China (Sino-Himalayan Region).{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}}The 300 tropical species within the Vireya section of subgenus Rhododendron occupy the Maritime Southeast Asia from their presumed Southeast Asian origin to Northern Australia, with 55 known species in Borneo and 164 in New Guinea. The species in New Guinea are native to subalpine moist grasslands at around 3,000 metres above sea level in the Central Highlands.{{sfnp|Argent|2006 |ref=Argent2006}} Subgenera Rhododendron and Hymenanthes, together with section Pentanthera of subgenus Pentanthera are also represented to a lesser degree in the Mountainous areas of North America and Western Eurasia. Subgenus Tsutsusi is found in the maritime regions of East Asia (Japan, Korea, Taiwan, East China), but not in North America or Eurasia.{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}}{{sfnp|JIN |DING |ZHANG |HONG |2010 |ref=JDZH}}In the United States, native Rhododendron mostly occur in lowland and montane forests in the Pacific Northwest, California, the Northeast, and the Appalachian Mountains.{{cn|date=June 2022}}

Ecology

Invasive species

Rhododendron ponticum has become invasive in IrelandNEWS,weblink Dramatic rescue of couple trapped in rhododendron forest, Irish Central, 18 July 2014, Bramhill, Nick, and the United Kingdom.NEWS,weblink A spectacular thug is out of control, The Guardian, 16 April 2017, Simons, Paul, 2 October 2017, It is an introduced species, spreading in woodland areas and replacing the natural understory. R. ponticum is difficult to eradicate, as its roots can make new shoots.

Insects

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 (caterpillars) of some butterflies and moths; see List of Lepidoptera that feed on rhododendrons.

Diseases

Major diseases include Phytophthora root rot, stem and twig fungal dieback.WEB,weblink Maintaining Healthy Rhododendrons and Azaleas in the Landscape, Harry A. J., Hoitink, Stephen, Nameth, Jim, Chatfield, ohioline.ag.ohio-state.edu, 26 February 2013,weblink" title="web.archive.org/web/20130605225226weblink">weblink 5 June 2013, Rhododendron bud blast, a fungal condition that causes buds to turn brown and dry before they can open, is caused by the fungus Pycnostysanus azaleae, which may be brought to the plant by the rhododendron leafhopper, Graphocephala fennahi.BOOK, The American Horticultural Society Encyclopedia of Gardening, Christopher, Brickell, Elvin, McDonald, NY, Dorling Kindersley Publishing, 1993, 978-1564582911,weblink {{rp|page=562}}

Cultivation

File:Rhododendronpark Bremen 14-05-09.jpg|thumb|right|Rhododendron-Park BremenRhododendron-Park BremenBoth species and hybrid rhododendrons (including azaleas) are used extensively as ornamental plants in landscaping in many parts of the world, including both temperate and (wiktionary:subtemperate|subtemperate) regions.{{sfnp|Craven |Goetsch |Hall |Brown |2008 |ref=Craven2008}} Many species and cultivars are grown commercially for the nursery trade.Rhododendrons can be propagated by air layering or stem cuttings.{{rp|540–541}} They can self-propagate by sending up shoots from the roots. Sometimes an attached branch that has drooped to the ground will root in damp mulch, and the resulting rooted plant then can be cut off the parent rhododendron.(File:Rhododendron wardii var puralbum.jpg|thumb|right|Rhododendron wardii var. puralbum)Rhododendrons are often valued in landscaping for their structure, size, flowers, and the fact that many of them are evergreen.BOOK, Huxley, A., Griffiths, M., Levy, Margot, 1992, New RHS Dictionary of Gardening, Macmillan, London, 978-0333474945, 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 Rhododendron arboreum and R. falconeri eventually growing to a height of {{convert|10|-|15|m|ft|2|abbr=on}} or more.

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 on the west coast (Oregon, Washington state and California). Large-scale commercial growing often selects for different characteristics than 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.

Horticultural divisions

Horticulturally, rhododendrons may be divided into the following groups:BOOK, RHS A-Z Encyclopedia of Garden Plants, 2008, Christopher, Brickell, Penguin Books, United Kingdom, 978-1405332965, 1136,

• Evergreen rhododendrons - large group of evergreen shrubs that vary greatly in size. Most rhododendron flowers are bell-shaped and have 10 stamens.
• Vireya (Malesian) rhododendrons: epiphytic tender shrubsWEB,weblink Chris, Callard, Vireya Rhododendrons – Welcome, vireya.net, 1998–2015, 26 February 2013,
• Azaleas – group of shrubs which have smaller and thinner leaves than evergreen rhododendrons. They are generally medium-sized shrubs with smaller funnel-shaped flowers that usually have 5 stamens:
  • Deciduous hybrid azaleas:WEB,weblink Deciduous Azaleas, Rhodyman.net, 26 February 2013,
    • Exbury hybrids – derived from the Knap Hill hybrids, developed by Lionel de Rothschild at the Exbury Estate in England.WEB,weblink My Fascination with Knap Hill Azaleas, Hyatt, Donald W., 24 September 2017, WEB,weblink Exbury Gardens, Hyatt, Donald W., 21 October 2017,
    • Ghent (Gandavense) hybrids – Belgian raisedJOURNAL,weblink Rescuing the Ghent and Rustica Flore Pleno Azaleas, Journal American Rhododendron Society, 38, 3, Skinner, Archie, Summer 1984, 26 February 2013,
    • Knap Hill hybrids – developed by Anthony Waterer at the Knap Hill Nursery in England.
    • Mollis hybrids – Dutch and Belgian raisedJOURNAL,weblink The Quarterly Bulletin of the American Rhododendron Society, 14, 1, Living, L.C., Mollis Azaleas, January 1960, 26 February 2013,
    • New Zealand Ilam hybrids – derived from Knap Hill/Exbury hybrids
    • Occidentale hybrids – English raised
    • Rustica Flore Pleno hybrids – sweet-scented, double-flowered
  • Evergreen hybrid azaleas:
    • Gable hybrids – raised by Joseph B. Gable in Pennsylvania.WEB,weblink The Rhododendron Legacy of Joe Gable, Hyatt, Donald W., 24 September 2017,
    • Glenn Dale hybrids – US 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 Â°C)
    • Oldhamii hybrids – dwarf hybrids raised at Exbury, England
    • Satsuki hybrids – Japanese raised, originally for bonsai
    • Shammarello hybrids – raised in northern OhioJOURNAL,weblink The Quarterly Bulletin of the American Rhododendron Society, 9, 4, Baldsiefen, Warren, Shammarello's Wonderland, October 1955, 26 February 2013,
    • Vuyk (Vuykiana) hybrids – raised in the NetherlandsJOURNAL,weblink The Quarterly Bulletin of the American Rhododendron Society, 33, 1, Nosal, Mathew A., The Vuykiana Azaleas, Winter 1979, 26 February 2013,
• Azaleodendrons – semi-evergreen hybrids between deciduous azaleas and rhododendrons

Planting and care

File:Nova Zembla Rhododendron plants growing in NJ in April.jpg|thumb|right|Nova Zembla Rhododendrons growing in a nursery in New JerseyNew JerseyLike 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.WEB,weblink Soil information for planting rhododendrons, American Rhododendron Society, 26 February 2013, Mulching and careful watering are important, especially before the plant is established.A new calcium-tolerant stock of rhododendrons (trademarked 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.WEB,weblink Lime Tolerant Rhododendrons, Millais Nurseries, 2 October 2017, NEWS, Bunny, Guinness, 17 November 2009,weblink The new lime-tolerant rhododendrons, The Telegraph, 26 February 2013,

Hybrids

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 weblink" title="web.archive.org/web/20110426161301weblink">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 flowersWEB, Fragrant Rhododendrons,weblink Francis, Richard, Wildeel.com, 11 March 2015, 25 January 2006,weblink" title="web.archive.org/web/20150708084734weblink">weblink 8 July 2015, —such as the Loderi hybrids, created by crossing Rhododendron fortunei and R. griffithianum.{{sfnp|Davidian |loc=Vol. II, plate 44 & 45 |ref=Davidian}} Other examples include the PJM hybrids, formed from a cross between Rhododendron carolinianum and R. dauricum, and named after Peter J. Mezitt of Weston Nurseries, Massachusetts.WEB, Mark H., Brand,weblink UConn Plant Database, Rhododendron 'PJM' Hybrids,weblink" title="web.archive.org/web/20130629153207weblink">weblink 29 June 2013,

Uses

Pharmacology

Rhododendron species have long been used in traditional medicine.JOURNAL, Popescu, R, Kopp, B, May 2013, The genus Rhododendron: an ethnopharmacological and toxicological review, J Ethnopharmacol, 147, 1, 42–62, 10.1016/j.jep.2013.02.022, 23454683, JOURNAL, O'Neill, A. R., Badola, H.K., Dhyani, P. P., Rana, S. K., 2017, Integrating ethnobiological knowledge into biodiversity conservation in the Eastern Himalayas, Journal of Ethnobiology and Ethnomedicine, 13, 1, 21, 10.1186/s13002-017-0148-9, 28356115, 5372287, free, Animal studies and in vitro research have 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.JOURNAL, Agarwal, S.S., Sharma Kalpana, Anti-inflammatory activity of flowers of Rhododendron arboreum (SMITH) in rat's hind paw oedema induced by various phlogistic agents, Indian Journal of Pharmacology, 20, 2, 86–89, 1988,weblink Xiong et al. have found that the root of the plant is able to reduce the activity of NF-κB in rats.JOURNAL, 10.1016/S1007-4376(09)60031-9, The effect of root of rhododendron on the activation of NF-κB in a chronic glomerulonephritis rat model, January 2009, Xiong, Jing, Zhu, Zhonghua, Liu, Jianshe, Wang, Yang, Journal of Nanjing Medical University, 23, 1, 73–78,

Toxicology

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 mad 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 BCE.Xenophon, Anabasis 4.8.19–21. Pompey's soldiers reportedly suffered lethal casualties following the consumption of honey made from Rhododendron deliberately left behind by Pontic forces in 67 BCE during the Third Mithridatic War.Strabo, Geography 12.3.18. Later, it was recognized that honey resulting from these plants has a slightly hallucinogenic and laxative effect.BOOK,weblinkweblink 2022-10-09, live, Grayanotoxins, Bad Bug Book: Handbook of foodborne pathogenic microorganisms and natural toxins, 2nd, Food and Drug Administration, 2012, 3 October 2017, The suspect rhododendrons are Rhododendron ponticum and Rhododendron luteum (formerly Azalea pontica), both found in northern Asia Minor. Eleven similar cases during the 1980s have been documented in Istanbul, Turkey.JOURNAL, Sütlüpmar, Nurhayat, Mat, Afife, Satganoglu, Yurdagül, amp, February 1993, Poisoning by toxic honey in Turkey, Archives of Toxicology, 67, 2, 148–150, 10.1007/BF01973687, 8481104, 9658996, 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. Rhododendron, including its stems, leaves and flowers, contains toxins that, if ingested by a cat's stomach, can cause seizures and even coma and death.WEB,weblink 10 plants that are poisonous to cats, The effects of R. ponticum were mentioned in the 2009 film Sherlock Holmes as a proposed way to arrange a fake execution.WEB,weblink Rhododendron poison – truth behind the science of Sherlock Holmes, Captain Skellett, A Schooner of Science, 27 December 2009, 26 February 2013, It was also mentioned in the third episode of Season 2 of BBC's Sherlock, speculated to have been a part of Sherlock's fake death scheme.{{citation needed |date=June 2020}}

Culture

Symbolism

(File:Pink Rhododendron Blossom Prashar Himachal Apr11 P1020872.jpg|thumb|State flower of Himachal Pradesh)In the language of flowers, the rhododendron symbolizes danger and to beware.WEB,weblink Language of Flowers – Flower Meanings and Flower Sentiments, www.languageofflowers.com, 26 November 2016, 24 November 2016,weblink" title="web.archive.org/web/20161124141728weblink">weblink dead, 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 arboreum is also the state tree of the state of Uttarakhand, India. Pink Rhododendron (Rhododendron campanulatum) is the state flower of Himachal Pradesh, India. Rhododendron is also the provincial flower of Jiangxi, China and the state flower of Nagaland, the 16th state of the Indian Union.Rhododendron maximum, the most widespread rhododendron of the Appalachian Mountains, is the state flower of the US state 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 the US state of Washington.

Literature

The nineteenth-century American poet and essayist Ralph Waldo Emerson in 1834 wrote a poem titled "The Rhodora, On Being Asked, Whence Is the Flower",File:Leon Wyczółkowski - Różowe azalie.jpg|thumb|Leon WyczółkowskiLeon WyczółkowskiIn 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,BOOK,weblink Something rotten, 978-0-14-303541-1, Fforde, Jasper, 26 July 2005, Penguin, and (Shades of Grey 1: The Road to High Saffron|Shades of Grey).WEB, Jasper Fforde,weblink Shades of Grey – An Interview with Jasper Fforde about Shades of Grey, Jasperfforde.com, 26 February 2013, Amongst the Zomi tribes in India and Myanmar, "Rhododendrons" called "Ngeisok" is used in a poetic manner to signify a lady.{{citation needed|date=May 2016}}In Daphne Du Maurier's novel Rebecca, the character of Rebecca is associated with "blood red" rhododendrons throughout the novel, perhaps due to the toxic roots of the plant mirroring the poisonous character of Rebecca. On the other hand, azaleas (a type of rhododendron) represent the second Mrs. De Winter.{{citation needed|date=May 2016}}In the young adult novel Walk Two Moons by Sharon Creech, the protagonist, Sal, and her friend, Phoebe, construct an elaborate story in which they suspect Phoebe's neighbor of murdering her husband and burying his body beneath a rhododendron in her yard. Chapter 14 of the book is entitled "The Rhododendron".

Culinary

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.BOOK, Puskal Prasad, Regmi, 1982, An introduction to Nepalese food plants, Royal Nepal Academy,weblink {{rp|51}} The flower, fresh or dried, is added to fish curry in the belief that it will soften the bones.{{rp|53}} 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.BOOK, Narain Singh, Chauhan, 1999, Medicinal and Aromatic Plants of Himachal Pradesh, 355, Indus Publishing,weblink 9788173870989,

Labrador tea

The herbal tea called Labrador tea (not a true tea) is made from one of three closely related species:

• Rhododendron tomentosum (Northern Labrador tea, previously Ledum palustre)
• Rhododendron groenlandicum, (Bog Labrador tea, previously Ledum groenlandicum or Ledum latifolium)
• Rhododendron neoglandulosum, (Western Labrador tea, or trapper's tea, previously Ledum glandulosum)

Conservation

In the UK the forerunner of the Rhododendron, Camellia and Magnolia Group (RCMG), The Rhododendron Society was founded in 1916.WEB,weblink Centenary – Background, Rhododendron, Camellia and Magnolia Group, 26 May 2016,weblink" title="web.archive.org/web/20160912182235weblink">weblink 12 September 2016, while in Scotland species are being conserved by the Rhododendron Species Conservation Group.WEB, John M. Hammond,weblink Conservation of Rhododendron Species and their historic Gardens, RSCG, 2 October 2017,

Cultural significance

In Uttarakhand, in north India, the Buransh flower is deeply embedded in local culture, playing a significant role in festivals like Holi and weddings, where it is used in garlands and decorations to bless attendees. The flower is also utilized in making a healthful, antioxidant-rich juice that is popular during local festivities and summer months. Additionally, Buransh flowers are incorporated into local arts and crafts, where they are used to make colorful necklaces and jewelry, symbolizing the spiritual and physical prosperity of the community.WEB,weblink Uttarakhand ka rajya pushp: Buraansh, Raebaar.com, 25 Apr 2024,

See also

• List of Award of Garden Merit rhododendrons
• List of Rhododendron diseases
• List of Rhododendron species
• List of Sections in Subgenus Rhododendron

References

Bibliography

Books and book chapters

• BOOK, Augustin Pyramus de Candolle, 1838, Prodromus systemati naturalis regni vegetabilis sive enumeratio contracta ordinum, generum specierumque plantarum huc usque cognitarum, juxta methodi naturalis normas digesta, 7,weblink Rhododendron, 719–728, Treuttel et Würtz, Paris, la, Candolle, Augustin Pyramus de Candolle, (also available online at Gallica)
• BOOK,weblink Sweet, Robert, The British Flower Garden, The Two Series, I, Robert Sweet (botanist), Drawings by E.D. Smith, James Ridgway & Sons, London, 1838,
• BOOK,weblink Hooker, Joseph Dalton, Hooker, William Jackson, The Rhododendrons of Sikkim-Himalaya: being an account, botanical and geographical, of the rhododendrons recently discovered in the mountains of eastern Himalaya, from drawings and descriptions made on the spot, during a government botanical mission to that country, Reeve, Benham, and Reeve, London, 1849, 2nd, 10.5962/bhl.title.11178,
• CONFERENCE,weblink James Leonard, Luteyn, Mary E., O'Brien, amp, Contributions Toward a Classification of Rhododendron: Proceedings of the International Rhododendron Conference, International Rhododendron Conference (The New York Botanical Garden, May 15–17, 1978), New York Botanical Garden Press, New York, 1980, 978-0-89327-221-0,
• BOOK, Davidian, H.H., The Rhododendron Species, 1982–1995, Timber Press, Portland, Oregon, Davidian, In four volumes: Vol. I. Lepidotes {{ISBN|0-917304-71-3}}, Vol. II. Elepidotes. Arboreum-Lacteum {{ISBN|0-88192-109-2}}, Vol. III. Elepidotes Continued, Neriiflorum-Thomsonii, Azaleastrum and Camtschaticum {{ISBN|0-88192-168-8}}, Vol. IV. Azaleas {{ISBN|0-88192-311-7}}.
• BOOK,weblink Cox, Peter A., amp, Cox, Kenneth N. E., The Encyclopedia of Rhododendron Species, 1997, Glendoick Publishing, 978-0-9530533-0-8, .
• BOOK,weblink registration, James, Cullen, Hardy Rhododendron Species: A Guide To Identification, Timber Press, 2005, 978-0881927238, Cullen2005,
• BOOK,weblink Blazich, Frank A., amp, D. Bradley, Rowe, July 2008, Rhododendron L., rhododendron and azalea, 943–951,weblinkweblink 2022-10-09, live, Franklin T., Bonner, Robert P., Karrfalt, The Woody Plant Seed Manual, Agr. Hdbk, 727, U.S. Dept. Agr. For. Serv., Washington, D.C.,

Articles

• JOURNAL,weblink Michael, Black, Historical Survey of Rhododendron Collecting With Emphasis on its Close Associations with Horticulture, The Quarterly Bulletin of the American Rhododendron Society, 23, 4, October 1969,
• JOURNAL,weblink Walter, Magor, A History of Rhododendrons, Journal American Rhododendron Society, 44, 4, Fall 1990,
• JOURNAL, Goetsch, Loretta A., Eckert, Andrew J., Hall, Benjamin D., July–September 2005, The molecular systematics of Rhododendron (Ericaceae): a phylogeny based upon RPB2 gene sequences, Systematic Botany, 30, 3, 616–626, 10.1600/0363644054782170, 51949019, Goetsch,

Subdivisions

Azaleas

• BOOK,weblink Wilson, E.H., Rehder, A., A Monograph of Azaleas; Rhododendron Subgenus Anthodendron, University Press, Cambridge, 1921, Publications of the Arnold Aboretum, no. 9,
• JOURNAL, John L., Creech, An Embryological Study in the Rhododendron Subgenus Anthodendron Endl., Botanical Gazette, 116, 3, 1955, 234–243, 2473343, 10.1086/335866, 83861676,

Tsutsusi

• JOURNAL, Chamberlain, D.F., Rae, S.J., amp, 1990, A revision of Rhododendron. IV. Subgenus Tsutsusi, Edinburgh Journal of Botany, 47, 2, 89–200, 10.1017/S096042860000319X, ChamRae1990, free,
• CONFERENCE,weblink Powell, E. Ann, Kron, Kathleen A, "Molecular systematics of Rhododendron subgenus Tsutsusi (Rhodoreae, Ericoideae, Ericaceae)", Botany 2004,weblink 2004, Abstract ID:147,
• JOURNAL, K.A., Kron, amp, E.A., Powell, Molecular systematics of Rhododendron subgenus Tsutsusi (Rhodoreae, Ericoideae, Ericaceae), Edinburgh Journal of Botany, 66, 1, March 2009, 81–95, 10.1017/S0960428609005071, free,
• JOURNAL, ZHANG Yue-Jiao, JIN Xiao-Feng, DING Bing-Yang, ZHU Jing-Ping, Pollen morphology of Rhododendron subgen. Tsutsusi and its systematic implications, Journal of Systematics and Evolution, 47, 2, 123–138, March 2009, 10.1111/j.1759-6831.2009.00011.x, 86594487,
• JOURNAL, JIN Xiao-Feng, DING Bing-Yang, ZHANG Yue-Jiao, HONG De-Yuan, A Taxonomic Revision Of Rhododendron subg. Tsutsusi sect. Brachycalyx (Ericaceae), Annals of the Missouri Botanical Garden, 97, 2, 163–190, 2010, 10.3417/2007139, 86507576, JDZH,

Vireya

• BOOK, Sleumer, Hermann Otto, An account of rhododendron in Malesia, P. Noordhoff, Groningen, 1966, . A reprint from Flora Malesiana ser. I, vol. 6, part 4. Pages 473 through 674.
• JOURNAL,weblink David G., Leach, The Discovery of the Malaysian Rhododendrons, The Quarterly Bulletin of the American Rhododendron Society, 32, 1, Winter 1978,
• BOOK, Argent, G., Rhododendrons of subgenus Vireya, 2006, Royal Horticultural Society, 978-1-902896-61-8, Argent2006,
• JOURNAL,weblink Brown, Gillian K., Craven, Lyn A., Udovicic, Frank, Ladiges, Pauline Y., August 2006, Phylogenetic relationships of Rhododendron section Vireya (Ericaceae) inferred from the ITS nrDNA region, Australian Systematic Botany, 19, 4, 329–342, 10.1071/SB05019, Brown2006, 15 July 2014,weblink" title="web.archive.org/web/20140715012754weblink">weblink
• JOURNAL, Hall, B.D., L.A., Craven, amp, L.A., Goetsch, 2006, The Taxonomy of Subsection Pseudovireya: Two distinctly different taxa within subsection Pseudovireya and their Relation to the Rooting of section Vireya within subgenus Rhododendron, Rhododendron Species, 1, 91–97, Yearbook of the Rhododendron Species Foundation, Federal Way, WA.
• JOURNAL, 10.3767/000651908X608070, Classification of the Vireya group of Rhododendron (Ericaceae), 2008, Craven, L.A., Goetsch, L.A., Hall, B.D., Brown, G.K., Blumea - Biodiversity, Evolution and Biogeography of Plants, 53, 2, 435–442, Craven2008,weblink
• JOURNAL, Goetsch, L.A., Craven, L.A., Hall, B.D., 2011, Major speciation accompanied the dispersal of Vireya Rhododendrons (Ericaceae, Rhododendron sect. Schistanthe) through the Malayan archipelago: Evidence from nuclear gene sequences, Taxon, 60, 4, 1015–1028, 10.1002/tax.604006,
• JOURNAL,weblink Peter, Adams, Evolution, Adaptive Radiation and Vireya Rhododendrons - Part I, Journal American Rhododendron Society, Fall 2012, 201–203, 18 June 2014,weblink" title="web.archive.org/web/20160820032816weblink">weblink 20 August 2016, dead,
• JOURNAL,weblink Peter, Adams, Evolution, Adaptive Radiation and Vireya Rhododendrons – Part II, Journal American Rhododendron Society, Spring 2013, 74–76, 18 June 2014,weblink" title="web.archive.org/web/20160820034157weblink">weblink 20 August 2016, dead,
• THESIS,weblink Biodiversity of the Vireya group of Rhododendron L. (Ericaceae) collections in New Zealand and their potential contribution to international conservation, Fayaz, A., PhD, Massey University, Turitea, New Zealand, 2012, Fayaz, 26 September 2017,

Separate genera

• JOURNAL, Craven, L.A., Diplarche and Menziesia transferred to Rhododendron (Ericaceae), Blumea - Biodiversity, Evolution and Biogeography of Plants, 56, 1, April 2011, 33–35, 10.3767/000651911X568594,weblink Craven2011,

Additional resources

Records of the Rhododendron Society of America reside at the Albert and Shirley Small Special Collections Library at the University of Virginia.

External links

{{Commons category|Rhododendron}}{{Wikispecies}}{{Wiktionary}}

• History of Rhododendron Discovery & Culture
• weblink" title="web.archive.org/web/20090606220644weblink">Rhododendrons from Turkey, Anatolia
• Danish Genebank Rhododendron
• Danish Genebank. Rhododendron in different countries
• German Genebank Rhododendron {{Webarchive|url=https://web.archive.org/web/20120315181800weblink |date=15 March 2012 }}
• Description of damage caused by Rhododendrons in the UK
• Information on rhododendrons at the Ericaceae web pages of Dr. Kron at Wake Forest University.
• Information on Vireyas
• weblink" title="web.archive.org/web/20181215224227weblink">Information+photos of hybrids and species
• Information on Rhododendrons by Marc Colombel, founder of the Société Bretonne du Rhododendron.
• Extensive information on rhododendron species: the history of their discovery, botanical details, toxicity, classification, cultural conditions, care for common problems, and suggestions for companion plants by Steve Henning.
• weblink" title="web.archive.org/web/20090130005655weblink">History of Rhododendrons
• Rhododendron in botanical garden Pruhonice-Czech republic {{Webarchive|url=https://web.archive.org/web/20171007024344weblink |date=7 October 2017 }}

Databases

• USDA Plants Database: Rhododendron
• ITIS Report: Rhododendron
• eFloras.org
  • Flora of North America: Rhododendron
  • Flora of China: Rhododendron
  • Annotated Checklist of the Flowering Plants of Nepal: Rhododendron

Societies

• American Rhododendron Society
  • The Quarterly Bulletin of the American Rhododendron Society 1947–1981
  • Journal of the American Rhododendron Society (JARS) 1982–
  • WEB,weblink Genus Rhododendron Taxonomic Tree, American Rhododendron Society, ARS2, Information Source: BOOK, Peter A., Cox, amp, Kenneth N. E., Cox, The Encyclopedia of Rhododendron Species, Glendoick Publishing, 1997, 978-0-9530533-0-8, .
• The Rhododendron, Camellia & Magnolia Group of the Royal Horticultural Society
• Rhododendron Species Foundation and Botanical Garden
• weblink" title="web.archive.org/web/20060408075911weblink">Société Finlandaise du Rhododendron
• Australian Rhododendron Society
• weblink" title="web.archive.org/web/20151105130749weblink">German Rhododendron Society
• New Zealand Rhododendron Association
• Danish Rhododendron Society
• Fraser South Rhododendron Society

Botanical gardens

• Royal Botanic Garden Edinburgh: Rhododendrons at the four Gardens {{Webarchive|url=https://web.archive.org/web/20180529031923weblink |date=29 May 2018 }}
• National Rhododendron Gardens Melbourne Australia

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