Rhododendron subg. Hymenanthes

Rhododendron subg. Hymenanthes is a subgenus of the genus Rhododendron, with a widespread distribution in the temperate Northern Hemisphere. The species are evergreen shrubs and small to medium-sized trees (up to 20 m tall), with medium-sized to large leaves (very large, over 40 cm long, in a few species). The flowers are large, produced in terminal trusses of 5-40 together.^[1]

Rhododendron subg. Hymenanthes
Rhododendron ponticum
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Ericales
Family:	Ericaceae
Genus:	Rhododendron
Subgenus:	Rhododendron subg. Hymenanthes (Blume) K.Koch
Sections
Ponticum Pentanthera

The subgenus includes two sections, Rhododendron sect. Ponticum, divided into 24 subsections and about 140 species, and (since 2005) Rhododendron sect. Pentanthera^[2]

Cultivation

This subgenus includes the majority of the larger evergreen rhododendrons widely grown as ornamental plants. Some species, notably Rhododendron ponticum, have escaped from cultivation and become invasive in some regions such as New Zealand.

Ponticum

Section Ponticum (24 subsections) includes:

• R. subsect. Arborea (4 species)
• R. subsect. Argyrophylla (6 species)
• R. subsect. Auriculata (one species, R. auriculatum)
• R. subsect. Barbata (2 species)
• R. subsect. Campanulata (2 species)
• R. subsect. Campylocarpa (4 species)
• R. subsect. Falconera (7 species)
• R. subsect. Fortunea (10 species)
• R. subsect. Fulgensia (2 species)
• R. subsect. Fulva (2 species)
• R. subsect. Glischra (5 species)
• R. subsect. Grandia (9 species)
• R. subsect. Griersoniana (one species, R. griersonianum)
• R. subsect. Irrorata (7 species)
• R. subsect. Lanata (one species, R. lanatum)
• R. subsect. Maculifera (6 species)
• R. subsect. Neriiflora (19 species)
• R. subsect. Parishia (3 species)
• R. subsect. Pontica (13 species)
• R. subsect. Selensia (5 species)
• R. subsect. Taliensia (20 species)
• R. subsect. Thomsonia (7 species)
• R. subsect. Venatora (one species, R. venator)
• R. subsect. Williamsiana (one species, R. williamsianum)

Arborea

Rhododendron subsect. Arborea is a subsection of section Ponticum in Hymenanthes consisting of 4 species of trees native to East Asia.^[3][4]

Image	Name	Distribution
	Rhododendron arboreum Smith 1805	China (Guizhou, S Xizang), Bhutan, India, Kashmir, Nepal, Sikkim, Sri Lanka, Thailand, Vietnam
	Rhododendron delavayi Franchet 1886	China (Guangxi, Guizhou, Sichuan, Xizang, Yunnan), Bhutan, India, Myanmar, Thailand, Vietnam
	Rhododendron lanigerum Tagg 1930	China (Xizang), India
	Rhododendron niveum J. D. Hooker 1852	China (Xizang), Bhutan, India (Sikkim)

Barbata

Rhododendron subsect. Barbata is a subsection of section Ponticum in Hymenanthes consisting of 5 species of small trees native to East Asia.^[5]

Image	Name	Distribution
	Rhododendron argipeplum Balf.f. & R.E.Cooper 1916	China (Xizang), Bhutan, India (Sikkim)
	Rhododendron barbatum Wall. ex G.Don 1834	China (Xizang), Bhutan, India (Sikkim), Nepal
	Rhododendron erosum Cowan 1937	China (Xizang), Arunachal Pradesh
	Rhododendron exasperatum Tagg 1930	China (Xizang), India, Myanmar
	Rhododendron succothii Davidian 1965	Bhutan, India (W Arunachal Pradesh)

Campanulata

Rhododendron subsect. Campanulata is a subsection of section Ponticum in Hymenanthes consisting of 2 species of shrubs native to East Asia.^[6]

Image	Name	Distribution
	Rhododendron campanulatum D. Don 1821	China (Xizang), Bhutan, India (Kashmir, Sikkim, Himachal Pradesh), Nepal
	Rhododendron gannanense Z. C. Feng & X. G. Sun 1992	China (Gansu)

Fortunea

Rhododendron subsect. Fortunea is a subsection of section Ponticum in Hymenanthes consisting of 37 species of shrubs or trees native to East Asia.^[7][8]

Image	Name	Distribution
	Rhododendron asterochnoum Diels 1921	China (Sichuan)
	Rhododendron auriculatum Hemsl. 1889	China (Shaanxi, Guizhou)
	Rhododendron bailiense Y.P.Ma, Zhang & D.F.Chamb. 2015	China (Guizhou)
	Rhododendron calophytum Franch. 1886	China (Chongqing, Gansu, Guizhou, Hubei, Shaanxi, Sichuan, Yunnan)
	Rhododendron chihsinianum Chun & W.P.Fang 1957	China (Guangxi)
	Rhododendron davidii Franch. 1886	China (Sichuan, Yunnan)
	Rhododendron decorum Franch. 1886	China (Guizhou, SW Sichuan, SE Xizang, Yunnan), Myanmar
	Rhododendron discolor Franch. 1895	China (Anhui, Chongqing, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Yunnan, Zhejiang)
	Rhododendron faithiae Chun 1934	China (Guangdong, Guangxi)
	Rhododendron fortunei Lindl. 1859	China (Anhui, Fujian, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Yunnan, Zhejiang)
	Rhododendron glanduliferum Franch. 1886	China (Yunnan)
	Rhododendron griffithianum Wight 1848	China (Xizang), Bhutan, N India, E Nepal, Sikkim
	Rhododendron guihainianum G.Z.Li 1995	China (Guangxi)
	Rhododendron hemsleyanum E.H.Wilson 1910	China (Sichuan)
	Rhododendron huangpingense Xiang Chen & Jia Y.Huang 2010	China (Guizhou)
	Rhododendron huanum W.P.Fang 1939	China (Chongqing, Guizhou, Sichuan, Yunnan)
	Rhododendron jinchangense Z.H.Yang 1997	China (Yunnan)
	Rhododendron jingangshanicum P.C.Tam 1982	China (Jiangxi)
	Rhododendron jiulongshanense Xiang Chen & Jia Y.Huang 2010	China (Guizhou)
	Rhododendron leigongshanense C.H.Yang, Z.G.Xie, Y.F.Yu & Z.R.Yang 2015	China (Guizhou)
	Rhododendron liboense Zheng R.Chen & K.M.Lan 2003	China (Guizhou)
	Rhododendron magniflorum W.K.Hu 1988	China (Guizhou)
	Rhododendron maoerense W.P.Fang & G.Z.Li 1984	China (Guangxi)
	Rhododendron miyiense W.K.Hu 1988	China (Sichuan)
	Rhododendron nymphaeoides W.K.Hu 1988	China (Sichuan)
	Rhododendron orbiculare Decne. 1877	China (Guangxi, Sichuan)
	Rhododendron oreodoxa Franch. 1886	China (Gansu, Hubei, Shaanxi, Sichuan, Xizang)
	Rhododendron platypodum Diels 1900	China (Chongqing)
	Rhododendron praeteritum Hutch. 1922	China (Gansu, Hubei, Hunan, Qinghai)
	Rhododendron praevernum Hutch. 1920	China (Guizhou, Hubei, Shaanxi, Sichuan, Yunnan)
	Rhododendron qiaojiaense L.M.Gao & D.Z.Li 2009	China (Yunnan)
	Rhododendron serotinum Hutch.	China (Yunnan), Vietnam
	Rhododendron sutchuenense Franch. 1895	China (Chongqing, Gansu, Guangxi, Guizhou, Hubei, Hunan, Shaanxi)
	Rhododendron vernicosum Franch. 1898	China (Sichuan, Xizang, Yunnan)
	Rhododendron verruciferum W.K.Hu 1989	China (Sichuan)
	Rhododendron wolongense W.K.Hu 1988	China (Sichuan)
	Rhododendron xiaoxidongense W.K.Hu 1990	China (Jiangxi)

Fulva

Rhododendron subsect. Fulva is a subsection of section Ponticum in Hymenanthes comprising 2 species of shrubs native to East Asia.^[9]

Image	Name	Distribution
	Rhododendron fulvum B. Balfour & W. W. Smith 1917	China (Sichuan, Xizang, W Yunnan), Myanmar
	Rhododendron uvariifolium Diels 1912	China (Sichuan, Xizang, Yunnan)

Grandia

Rhododendron subsect. Grandia is a subsection of section Ponticum in Hymenanthes that comprises 15 species of trees with large leaf blades covered with trichomes native to East Asia.^[10][11]

Image	Name	Distribution
	Rhododendron balangense W.P.Fang 1983	China (Sichuan)
	Rhododendron grande Wight 1847	China(Xizang), Bhutan, India (Arunachal Pradesh, Sikkim), Nepal
	Rhododendron kesangiae D.G.Long & Rushforth 1988 publ. 1989	Bhutan
	Rhododendron macabeanum G.Watt ex Balf.f. 1920	China (Xizang), Myanmar
	Rhododendron magnificum Kingdon Ward 1935	China (Xizang)
	Rhododendron montroseanum Davidian 1979	China (Xizang)
	Rhododendron oreogenum L. C. Hu 1992	China (Xizang)
	Rhododendron praestans I. B. Balfour & W. W. Smith 1916	China (Xizang, Yunnan)
	Rhododendron protistum I. B. Balfour & Forrest 1920	China (Xizang, Yunnan), Myanmar
	Rhododendron pudorosum Cowan 1937	China (Xizang)
	Rhododendron sidereum I. B. Balfour 1920	China (Yunnan), Myanmar
	Rhododendron sinogrande I. B. Balfour & W. W. Smith 1916	China (Xizang, Yunnan), Myanmar
	Rhododendron suoilenhense D.F.Chamb., N.T.T.Huong & Rushforth 2020	Vietnam
	Rhododendron watsonii Hemsley & E. H. Wilson 1910	China (Gansu, Sichuan)
	Rhododendron wattii Cowan 1936	India (Assam)

Pontica

Rhododendron subsect. Pontica is a subsection of section Ponticum in Hymenanthes consisting of 13 species of shrubs to small trees native to North America, Europe, and East Asia.^[12]

Image	Name	Distribution
	Rhododendron aureum Georgi 1775	China (Jilin, Liaoning), Japan, Korea, Mongolia, Russia
	Rhododendron brachycarpum D.Don ex G.Don 1834	Japan and Korea
	Rhododendron catawbiense Michx. 1803	United States (West Virginia south to northern Alabama.)
	Rhododendron caucasicum Pall. 1784	Transcaucasus and Anatolia
	Rhododendron degronianum Carrière	Japan (-Honshu)
	Rhododendron hyperythrum Hayata 1913	Taiwan
	Rhododendron japonoheptamerum Kitam. 1987	Japan
	Rhododendron macrophyllum D.Don ex G.Don	United States (Washington, California and northern Oregon), Canada (British Columbia)
	Rhododendron makinoi Tagg ex Nakai 1834	Japan
	Rhododendron maximum L. 1753	Alabama north to coastal Nova Scotia.
	Rhododendron ponticum L. 1762	Bulgaria, Lebanon-Syria, North Caucasus, Portugal, Spain, Transcaucasus, Turkey
	Rhododendron smirnowii Trautv. ex Regel 1885	Transcaucasus, Turkey
	Rhododendron ungernii Trautv. ex Regel 1885	Transcaucasus, Turkey

Venatora

Image	Name	Distribution
	Rhododendron venator Tagg ex L. Rothschild 1933	China (Xizang)

Williamsiana

Rhododendron subsect. Williamsiana is a subsection of section Ponticum in Hymenanthes consisting of 2 species^[13]

Image	Name	Distribution
	Rhododendron venator Rehder & E.H.Wilson 1913	China (Guizhou, Sichuan, Xizang, Yunnan)
	Rhododendron leishanicum W.P.Fang & X.S.Zhang 1983	China (Guizhou)

Pentanthera

Rhododendron sect. Pentanthera is a section of subgenus Hymenanthes in the genus Rhododendron. It comprises 15-16 species of deciduous shrubs native to temperate regions of the Northern Hemisphere.

It includes two subsections:

• Pentathera
• Sinensia

Pentanthera

See also: North American azaleas

Species include:

Image	Name	Distribution
	Rhododendron alabamense Alfred Rehder, 1921 (Alabama azalea)	United States (Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, Tennessee)
	Rhododendron arborescens John Torrey, 1824	United States (West Virginia, Pennsylvania, Tennessee, North Carolina, Georgia and Alabama.)
	Rhododendron atlanticum Alfred Rehder, 1921	United States (New Jersey south to Georgia.)
	Rhododendron austrinum (Small) Rehder 1917	United States (Alabama, Florida, Georgia, and Mississippi)
	Rhododendron calendulaceum John Torrey, 1824	United States (southern Pennsylvania and Ohio to northern Georgia.)
	Rhododendron canadense (L.) Torr.	Canada in Newfoundland and extends into eastern Ontario and the United States from New York, New Jersey, and at high altitudes in the Appalachian Mountains further south to Pennsylvania.
	Rhododendron canescens (Michx.) Sweet 1889	United States(Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia )
	Rhododendron colemanii Ronald F. Miller, 2008	United States(Alabama and western Georgia)
	Rhododendron cumberlandense Emma Lucy Braun, 1941	United States (Kentucky, Tennessee, Georgia, Alabama, and North Carolina.)
	Rhododendron eastmanii Kathleen Anne Kron, 1999	United States (South Carolina)
	Rhododendron flammeum (Michx.) Sarg. 1917	United States(Georgia and South Carolina)
	Rhododendron luteum Sweet 1911 (yellow azalea, honeysuckle azalea)	southern Russia; and in Asia
	Rhododendron occidentale Torr. & A.Gray 1876	United States(Oregon, California)
	Rhododendron periclymenoides (Michx.) Shinners 1962 (pink azalea, pinxterbloom azalea, pinxter flower)	United States(southern New York south to Georgia)
	Rhododendron prinophyllum (Small) Millais 1917 (rose azalea, roseshell azalea)	Eastern United States
	Rhododendron prunifolium (Small) Millais 1917	United States( Georgia, Alabama )
	Rhododendron viscosum (L.) Torr. 1824 (Swamp azalea)	Eastern United States

Sinensia

Species include:

Image	Name	Distribution
	Rhododendron molle (Blume) G.Don 1834	S. China
	Rhododendron japonicum[14] (A.Gray) Suringar, 1908	Japan (Honshu, Shikoku, N. Kyushu).

The section is closely related to sect. Rhodora, differing from it in the flower corolla having five fully developed lobes, whereas sect. Rhodora has the upper three lobes joined into a single three-lipped lobe.

Cultivation

Most (but not all) of the cultivated azaleas belong to species in this section, and hybrids derived from them.