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69-597: Former subgenera : Rhododendron ( / ˌ r oʊ d ə ˈ d ɛ n d r ən / ; pl. : rhododendra ) is a very large genus of about 1,024 species of woody plants and 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. It

138-462: 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 . Rhododendron is the largest genus in the family Ericaceae , with over 1,000 species, (though estimates vary from 850 to 1,200) and is morphologically diverse. Consequently, the taxonomy has been historically complex. Although Rhododendrons had been known since

207-430: 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 , 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

276-452: 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 B and C , with two each, while Azaleastrum had one section in each of A and C . Thus subgenera Azaleastrum and Pentanthera needed to be disassembled, and Rhododendron , Hymenanthes and Tsutsusi correspondingly expanded. In addition to

345-539: A hierarchy of subgenus, section, subsection, and species. Terminology from the Sleumer (1949) system is frequently found in older literature, with five subgenera and is as follows; In the later traditional classification, attributed to Chamberlain (1996), and as used by horticulturalists and the American Rhododendron Society , Rhododendron has eight subgenera based on morphology , namely

414-651: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

483-842: 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. In the United States, native Rhododendron mostly occur in lowland and montane forests in the Pacific Northwest , California , the Northeast , and the Appalachian Mountains . Rhododendron ponticum has become invasive in Ireland and

552-628: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

621-419: 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 B ( Hymenanthes ) and C ( Azaleastrum ), although the name was retained in section Pentanthera (14 species) which

690-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

759-411: 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) and by Craven et al. (2008) shown in ( parenthetical italics ). Older ranks such as Series (groups of species) are no longer used but may be found in the literature, but

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828-415: A subgenus of Rhododendron . In 1987 Spethmann, adding phytochemical features proposed a system with fifteen subgenera grouped into three 'chorus' subgenera. A number of closely related genera had been included together with Rhododendron in a former tribe, Rhodoreae. These have been progressively incorporated into Rhododendron . Chamberlain and Rae moved the monotypic section Tsusiopsis together with

897-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

966-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

1035-470: Is a genus of shrubs and small to (rarely) large trees , the smallest species growing to 10–100 cm (4–40 in) tall, and the largest, R. protistum var. giganteum , reported to 30 m (100 ft) tall. The leaves are spirally arranged; leaf size can range from 1–2 cm (0.4–0.8 in) to over 50 cm (20 in), exceptionally 100 cm (40 in) in R. sinogrande . They may be either evergreen or deciduous . In some species,

1104-612: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

1173-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

1242-457: Is subgenus Rhododendron , containing nearly half of all known species and all of the lepidote species. For a comparison of the Sleumer and Chamberlain systems, see Goetsch et al. (2005) Table 1. 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

1311-917: 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 Jeju Province in South Korea, 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. Azaleas make up two subgenera of Rhododendron . They are distinguished from "true" rhododendrons by having only five anthers per flower. The common and generic name comes from Ancient Greek ῥόδον rhódon  'rose' and δένδρον déndron  'tree'. Rhododendron

1380-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

1449-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

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1518-824: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

1587-732: 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. Subgenera Rhododendron and Hymenanthes , together with section Pentanthera of subgenus Pentanthera are also represented to

1656-589: The Solomon Islands . The centres of diversity are in the Himalayas and Maritime Southeast Asia , 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

1725-528: The United Kingdom . 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. 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

1794-449: The larvae ( caterpillars ) of some butterflies and moths ; see List of Lepidoptera that feed on rhododendrons. Major diseases include Phytophthora root rot, stem and twig fungal dieback. 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 . In

1863-419: The nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

1932-436: The nursery trade. Rhododendrons can be propagated by air layering or stem cuttings. 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. They can also be reprodcued by seed dispersal - or by horticulturalists collecting the spent flower buds and saving ad drying

2001-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

2070-584: The American Rhododendron Society still uses a similar device, called Alliances The system used by the World Flora Online as of December 2023 uses six subgenera, four of which are divided further: Species 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

2139-485: 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 ). In 1986 Philipson & Philipson raised two sections of subgenus Aleastrum ( Mumeazalea , Candidastrum ) to subgenera, while reducing genus Therorhodion to

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2208-738: The UK the forerunner of the Rhododendron, Camellia and Magnolia Group (RCMG), The Rhododendron Society was founded in 1916. while in Scotland species are being conserved by the Rhododendron Species Conservation Group. Both species and hybrid rhododendrons (including azaleas) are used extensively as ornamental plants in landscaping in many parts of the world, including both temperate and subtemperate regions. Many species and cultivars are grown commercially for

2277-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

2346-570: 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. He listed five species under Rhododendron : R.   ferrugineum (the type species ), R. dauricum , R. hirsutum , R. chamaecistus (now Rhodothamnus chamaecistus (L.) Rchb.) and R. maximum . At that time he considered

2415-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

2484-737: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

2553-558: 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, used slightly different numeration. Soon, as more species became available in

2622-422: The heath complex in oak-heath forests in eastern North America. 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. Rhododendron are characterised by having inflorescences with scarious (dry) perulae ,

2691-633: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

2760-518: The later modifications introduced by Chamberlain et al. . The major finding of Goetsch and colleagues was that all species examined (except R. camtschaticum , subgenus Therorhodion ) formed three major clades which they labelled A , B , and C , with the subgenera Rhododendron and Hymenanthes as monophyletic groups nested within clades A and B , respectively. By contrast subgenera Azaleastrum and Pentanthera were polyphyletic , while R. camtschaticum appeared as

2829-498: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Rhododendron hirsutum Rhododendron hirsutum , commonly known as the hairy alpenrose is one of the species of Rhododendron native to the mountains of Europe . It occurs widely in the Alps except for the southwestern region (approximately south and west of

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2898-489: The monotypic genus Tsusiophyllum into section Tsutsusi , while Kron & Judd reduced genus Ledum to a subsection of section Rhododendron . Then Judd & Kron moved two species ( R.   schlippenbachii and R.   quinquefolium ) from section Brachybachii , subgenus Tsutsusi and two from section Rhodora , subgenus Pentanthera ( R. albrechtii , R. pentaphyllum ) into section Sciadorhodion , subgenus Pentanthera . Finally Chamberlain brought

2967-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

3036-573: 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). The 300 tropical species within the Vireya section of subgenus Rhododendron occupy

3105-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

3174-415: 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

3243-425: 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". Bentham and Hooker used a similar scheme, but called the divisions "Series". It was not until 1893 that Koehne appreciated

3312-471: The presence of scales (lepidote), deciduousness of leaves, and the floral and vegetative branching patterns, after Sleumer (1980). 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

3381-541: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

3450-519: 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

3519-470: The same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but the French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or

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3588-408: The scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of a species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in

3657-489: The seed for later germination and planting. Genus The composition of a genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of

3726-604: 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 Rhododendron referred to this series concept as the Balfourian system. That system continued up to modern times in Davidian's four volume The Rhododendron Species . The next major attempt at classification

3795-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

3864-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

3933-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

4002-567: The then known six species of Azalea that he had described earlier in 1735 in his Systema Naturae as a separate genus. 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

4071-577: The two separate genera included under Rhododendron by Chamberlain ( Ledum , Tsusiophyllum ), Goetsch et al. . added Menziesia (clade 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

4140-410: The type species. For instance Rhodora (Linnaeus 1763) for Rhododendron canadense , Vireya ( Blume 1826) and Hymenanthes (Blume 1826) for Rhododendron metternichii , now R. degronianum . Meanwhile, other botanists such as Salisbury (1796) and Tate (1831) began to question the distinction between Azalea and Rhododendron , and finally in 1836, Azalea was incorporated into Rhododendron and

4209-551: 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, 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

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4278-576: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

4347-487: The various systems together in 1996, with 1,025 species divided into eight subgenera. Goetsch (2005) provides a comparison of the Sleumer and Chamberlain schemata (Table 1). Rhododendron Choniastrum Hymenanthes Azaleastrum 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

4416-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

4485-530: Was a distinct subclade in  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. (See schemata under Subgenera .) Subsequent research has supported the revision by Goetsch, although has largely concentrated on further defining the phylogeny within the subdivisions. In 2011 the two species of Diplarche were also added to Rhododendron , incertae sedis . This genus has been progressively subdivided into

4554-512: 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.", 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

4623-400: Was derived from axils from previous year's shoots or the lowest scaly leaves. Following the cladistic analysis of Goetsch et al. (2005) this scheme was simplified, based on the discovery of three major clades (A, B, C) as follows. Clade A Clade B Clade C Sister taxon The larger subgenera are further subdivided into sections and subsections Some subgenera contain only

4692-467: Was moved to subgenus Hymenanthes . Of the remaining three sections, monotypic Viscidula was discontinued by moving R.   nipponicum to Tsutsusi ( C ), while Rhodora (2 species) was itself polyphyletic and was broken up by moving R.   canadense to section Pentanthera ( B ) and R.   vaseyi to section Sciadorhodion , which then became a new section of subgenus Azaleastrum  ( C ). Subgenus Tsutsusi ( C )

4761-411: Was reduced to section status retaining the name, and included in subgenus Azaleastrum . Of the three minor subgenera, all in C , two were discontinued. The single species of monotypic subgenus Candidastrum ( R.   albiflorum ) was moved to subgenus Azaleastrum , section Sciadorhodion . Similarly the single species in monotypic subgenus Mumeazalea ( R.   semibarbatum ) was placed in

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