Editing Rhododendron (section)

=== Modern classification ===
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''"<ref name=Sleumer49>{{cite journal |last=Sleumer |first=H |year=1949 |title=Ein System der Gattung ''Rhododendron'' L. |journal=Bot. Jahrb. Syst. |volume=74 |pages=511–553}}</ref> and subsequent refinements.<ref name=Sleumer66/><ref name=Sleumer80/> 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'').<ref name=Sleumer80/><ref>{{cite journal |first=J. |last=Cullen |title=A revision of Rhododendron I. Subgenus Rhododendron sections Rhododendron and Pogonanthum |journal=Notes from the Royal Botanic Garden Edinburgh |volume=39 |issue=1 |date=1980 |issn=0080-4274}}</ref> In 1986 Philipson & [[Melva Philipson|Philipson]] raised two sections of subgenus ''Aleastrum'' (''Mumeazalea'', ''Candidastrum'') to subgenera, while reducing genus ''Therorhodion'' to a subgenus of ''Rhododendron''.<ref>{{cite journal |last1=Philipson |first1=W.R. |last2=Philipson |first2=M.N. |year=1986 |title=A revision of Rhododendron III. Subgenera Azaleastrum, Mumeazalea, Candidastrum and Therorhodion |journal=Notes from the Royal Botanic Garden Edinburgh |volume=44 |pages=1–23 |issn=0080-4274}}</ref> In 1987 Spethmann, adding [[phytochemical]] features proposed a system with fifteen subgenera grouped into three 'chorus' subgenera.<ref>{{cite journal |last1=Spethmann |first1=W |year=1987 |title=A new infrageneric classification and phylogenetic trends in the genus ''Rhododendron'' (''Ericaceae'') |journal=Plant Systematics and Evolution |volume=157 |issue= 1–2|pages=9–31 |issn=1615-6110 |doi=10.1007/BF00939178|bibcode=1987PSyEv.157....9S |s2cid=35751500}}</ref>

A number of closely related genera had been included together with ''Rhododendron'' in a former tribe, Rhodoreae. These have been progressively incorporated into ''Rhododendron''.<ref>{{cite journal | last1 = Stevens | first1 = PF | year = 1971| title = A classification of the Ericaceae: subfamilies and tribes | journal = Botanical Journal of the Linnean Society | volume = 64 | issue = 1| pages = 1–53 | doi = 10.1111/j.1095-8339.1971.tb02133.x}}</ref> 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''.<ref>{{cite journal | last1 = Kron | first1 = K. A. | last2 = Judd | first2 = W. S. | year = 1990 | title = Phylogenetic relationships within the Rhodoreae (Ericaceae) with specific comments on the placement of ''Ledum'' | journal = Systematic Botany | volume = 15 | issue = 1| pages = 57–68 | doi=10.2307/2419016| jstor = 2419016| bibcode = 1990SysBo..15...57K }}</ref> Then Judd & Kron moved two species ([[Rhododendron schlippenbachii|''R.''&nbsp;''schlippenbachii'']] and [[Rhododendron quinquefolium|''R.''&nbsp;''quinquefolium'']]) from section ''Brachybachii'', subgenus ''Tsutsusi'' and two from section ''Rhodora'', subgenus ''Pentanthera'' (''[[Rhododendron albrechtii|R.&nbsp;albrechtii]]'', ''[[Rhododendron pentaphyllum|R.&nbsp;pentaphyllum]]'') into section ''Sciadorhodion'', subgenus ''Pentanthera''.<ref>{{cite journal | last1 = Judd | first1 = W. S. | last2 = Kron | first2 = K. A. | year = 1995 | title = A revision of ''Rhododendron''. VI. Subgenus ''Pentanthera'' (sections ''Sciadorhodion'', ''Rhodora'', and ''Viscidula'') | journal = Edinburgh Journal of Botany | volume = 52 | issue = 1| pages = 1–54 | doi=10.1017/s0960428600001906| doi-access = free }}</ref> Finally Chamberlain brought 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&nbsp;1).{{sfnp|Goetsch |Eckert |Hall|2005 |ref=Goetsch}}{{sfnp|Brown |Craven |Udovicic |Ladiges |2006 |ref=Brown2006}}<ref name=Spady/><ref name=Chamberlain/>{{sfnp|Cullen |2005 |ref=Cullen2005}}