Rhododendron

Source: Wikipedia, the free encyclopedia.
For other uses, see Rhododendron (disambiguation).

Rhododendron
Temporal range: 52–0 
Ma
 Ypresian - present[1]
Rhododendron ferrugineum
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Ericales
Family: Ericaceae
Subfamily: Ericoideae
Tribe: Rhodoreae
Genus: Rhododendron
L.[2]
Type species
Rhododendron ferrugineum
Subgenera[3]

Former subgenera:

Synonyms[4]
List
    • 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 (

Himalayan region, but smaller numbers occur elsewhere in Asia, and in North America, Europe and Australia.[5]

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 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.[6]

anthers
per flower.

Etymology

The common and generic name comes from

Ancient Greek ῥόδον rhódon 'rose' and δένδρον déndron 'tree'.[7][8][9]

Description

Rhododendron in the Carpathian Mountains of Western Ukraine

Rhododendron is a genus of

oak-heath forests in eastern North America.[13][14]

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.[3]

Rhododendron are characterised by having

stamens that have no appendages, and agglutinate (clumped) pollen.[15]

Taxonomy

Rhododendrons (Guras) at Ghorepani, Nepal
Rhododendron forest in Nepal
Rhododendron in Japan
A garden with tall Rhododendrons in Lynnwood, Washington
Rhododendron (গুরাস), Sandakphu, West Bengal, India
Azalea, Texas Gulf Coast
Bonsai

Rhododendron is the largest genus in the family Ericaceae, with over 1,000 species,[16][17] (though estimates vary from 850 to 1,200)[18][19] and is morphologically diverse. Consequently, the taxonomy has been historically complex.[15]

Early history

Although Rhododendrons had been known since the description of

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.[2][20] 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 the then known six species of Azalea[21] that he had described earlier in 1735 in his Systema Naturae as a separate genus.[22][23]

Linnaeus' six species of Azalea were

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,[22][23] although other authors such as Candolle, who described six sections,[28]
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

Bentham and Hooker used a similar scheme, but called the divisions "Series".[31] 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 Rhododendron[32] referred to this series concept as the Balfourian system. That system continued up to modern times in Davidian's four volume The Rhododendron Species.[33]

Modern classification

The next major attempt at classification was by

International Code of Botanical Nomenclature, culminating in 1949 with his "Ein System der Gattung Rhododendron"[34] and subsequent refinements.[35][36]
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).[36][37] In 1986 Philipson & Philipson raised two sections of subgenus Aleastrum (Mumeazalea, Candidastrum) to subgenera, while reducing genus Therorhodion to a subgenus of Rhododendron.[38] In 1987 Spethmann, adding phytochemical features proposed a system with fifteen subgenera grouped into three 'chorus' subgenera.[39]

A number of closely related genera had been included together with Rhododendron in a former tribe, Rhodoreae. These have been progressively incorporated into Rhododendron.

Ledum to a subsection of section Rhododendron.[42] 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.[43] 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 1).[3][15][23][44][45]

Phylogeny

Cladogram of genus Rhododendron
(Goetsch et al. 2005)
A

Rhododendron

Choniastrum

B

Hymenanthes

C

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

RPB2,[3] 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..[3][47]

The major finding of Goetsch and colleagues was that all species examined (except

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 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 the two separate genera included under Rhododendron by Chamberlain (

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 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 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) 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 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 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.[3] (See schemata under Subgenera.)[47]

Taxonomic changes within genus Rhododendron
Chamberlain (1996) Goetsch (2005)
Genus Subgenus Section Species Subgenus Section
Menziesa 9 species Azaleastrum
C		 Sciadorhodion
Rhododendron Candidastrum R. albiflorum
Pentanthera Sciadorhodion 4 species
Rhodora R. vaseyi
R. canadense Hymenanthes
B		 Pentanthera
Pentanthera 14 species
Viscidula R. nipponicum Azaleastrum
C		 Tsutsusi
Tsutsusi Brachycalyx 15 species
Tsutsusi 65 species
Mumeazalea R. semibarbatum
Azaleastrum Choniastrum 11 species Choniastrum
A

Subsequent research has supported the revision by Goetsch, although has largely concentrated on further defining the phylogeny within the subdivisions.[48] In 2011 the two species of Diplarche were also added to Rhododendron, incertae sedis.[49]

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

deciduousness of leaves, and the floral and vegetative branching patterns, after Sleumer (1980).[3][15][36] 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.[51]
The largest of these 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.[3]

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.

Deciduous Rhododendron luteum in fall color
Evergreen azalea Rhododendron kaempferi
Evergreen azalea cultivar leaf color before shedding
Rhododendron after freezing rain
Morphological classification of Rhododendron
(Chamberlain 1996)[44]
Inflorescence buds Leaf scales Leaf shoots Leaves Subgenus Section
Terminal Present Rhododendron
Absent Previous year Evergreen Hymenanthes
Deciduous Pentanthera Pentanthera
Rhodora
Viscidula
Lowest leaves Pentanthera Sciadorhodion
Tsutsusi
Lateral Evergreen Azaleastrum
Deciduous Candidastrum
Mumeazalea
Therorhodion

Following the

cladistic analysis of Goetsch et al. (2005)[3] this scheme was simplified, based on the discovery of three major clades
(A, B, C) as follows.

Clade A

Clade B

  • Subgenus
    elepidotes (without scales), including deciduous azaleas. 2 sections, about 140–225 species, type R. degronianum
    .

Clade C

Sister taxon

Sections and subsections

The larger subgenera are further subdivided into sections and subsections[51] 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)[3] and by Craven et al. (2008)[48] 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[50]

  • 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[52]
      )
  • Subgenus Hymenanthes (Blume) K.Koch (1 section, 224 species) (Increased to two sections)
    • Ponticum G. Don (24 subsections)
    • (Pentanthera (G. Don) Pojarkova (2 subsections – new section, moved from subgenus Pentanthera)
  • Subgenus Pentanthera (G. Don) Pojarkova (4 sections, 23 species) (Discontinued)
  • 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 December 2023 uses six subgenera, four of which are divided further:[53]

Species

Further information: List of Rhododendron species

Distribution and habitat

Rhododendron fallacinum photographed in situ on Mount Kinabalu, Borneo

Species of the genus Rhododendron are widely distributed between latitudes 80°N and 20°S and are

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).[3]

The 300

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.[3][30]

In the United States, native Rhododendron mostly occur in lowland and montane forests in the Pacific Northwest, California, the Northeast, and the Appalachian Mountains.[58]

Ecology

Invasive species

Rhododendron ponticum has become invasive in Ireland[59] and the United Kingdom.[60] 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

moths
; see List of Lepidoptera that feed on rhododendrons.

Diseases

Main article: List of rhododendron diseases

Major diseases include Phytophthora root rot, stem and twig fungal dieback.[61]

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.[62]: 562 

Conservation

In the UK the forerunner of the Rhododendron, Camellia and Magnolia Group (RCMG), The Rhododendron Society was founded in 1916.[63] while in Scotland species are being conserved by the Rhododendron Species Conservation Group.[64]

Cultivation

Rhododendron-Park Bremen, Germany

Both species and hybrid rhododendrons (including azaleas) are used extensively as

nursery
trade.

Rhododendrons can be propagated by air layering or stem cuttings.[62]: 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. They can also be reprodcued by seed dispersal - or by horticulturalists collecting the spent flower buds and saving ad drying the seed for later germination and planting.

Rhododendron wardii var. puralbum

Rhododendrons are often valued in landscaping for their structure, size, flowers, and the fact that many of them are evergreen.[65] 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 10–15 m (32.81–49.21 ft) or more.[65]

Commercial growing

Rhododendrons are grown commercially in many areas for sale, and seeds were occasionally collected in the wild, a practice now rare in most areas due to the Nagoya Protocol. 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.[66]

Horticultural divisions

Horticulturally, rhododendrons may be divided into the following groups:[22][67]

  • 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 shrubs[68]
  • 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:[69]
      • Exbury hybrids – derived from the Knap Hill hybrids, developed by Lionel de Rothschild at the Exbury Estate in England.[70][71]
      • Ghent (Gandavense) hybrids – Belgian raised[72]
      • Knap Hill hybrids – developed by Anthony Waterer at the Knap Hill Nursery in England.[70]
      • Mollis hybrids – Dutch and Belgian raised[73]
      • New Zealand Ilam hybrids – derived from Knap Hill/Exbury hybrids
      • Occidentale hybrids – English raised
      • Rustica Flore Pleno hybrids – sweet-scented, double-flowered[72]
    • Evergreen hybrid azaleas:
      • Gable hybrids – raised by Joseph B. Gable in Pennsylvania.[74]
      • 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 °C)
      • Oldhamii hybrids – dwarf hybrids raised at Exbury, England
      • Satsuki hybrids – Japanese raised, originally for bonsai
      • Shammarello hybrids – raised in northern Ohio[75]
      • Vuyk (Vuykiana) hybrids – raised in the Netherlands[76]
  • Azaleodendrons – semi-evergreen hybrids between deciduous azaleas and rhododendrons

Planting and care

Nova Zembla Rhododendrons growing in a nursery in New Jersey.

Like other

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.[77]
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.[78][79]

Hybrids

Rhododendrons are extensively hybridized in cultivation, and natural hybrids often occur in areas where species ranges overlap. There are over 28,000

Rhododendron carolinianum and R. dauricum, and named after Peter J. Mezitt of Weston Nurseries, Massachusetts.[82]

Toxicity

Main article: Grayanotoxin

Some species of rhododendron are poisonous to grazing animals because of a

Asia Minor. Eleven similar cases during the 1980s have been documented in Istanbul, Turkey.[86] 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.[87]

Uses

Rhododendron species have long been used in traditional medicine.

phenolic compounds and saponins the plant contains.[90] Xiong et al. have found that the root of the plant is able to reduce the activity of NF-κB in rats.[91]

In Nepal, 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.[92]: 51  The flower, fresh or dried, is added to fish curry in the belief that it will soften the bones.[92]: 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.[93]

Labrador tea

Main article: Labrador tea

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

In culture

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.[94]

The rhododendron is the national flower of Nepal.

State flower of Himachal Pradesh

In the language of flowers, the rhododendron symbolizes danger and to beware.[95]

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.

Amongst the

Zomi tribes in India and Myanmar, "Rhododendrons" called "Ngeisok" is used in a poetic manner to signify a lady.[citation needed]

Leon Wyczółkowski
, Pink Rhododendrons, 1903

In media

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".

Rhododendrons play a role and are soliloquized in

Daphne Du Maurier's novel Rebecca (1938)[citation needed] and in Sharon Creech's young adult novel Walk Two Moons (1994). British author Jasper Fforde also uses rhododendron as a motif throughout many of his books, e.g. the Thursday Next series[96] and Shades of Grey (2009).[97]

The effects of R. ponticum were mentioned in the 2009 film

fake execution.[98] 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
]

See also

References

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Bibliography

Books and book chapters

Articles

Subdivisions

The cultural requirements of azaleas and rhododendrons are so similar that this 1960 U.S. Department of Agriculture publication treated them together.

Azaleas

Tsutsusi

Vireya

Separate genera

Additional resources

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

Wikimedia Commons has media related to Rhododendron.
Wikispecies has information related to Rhododendron.
Look up rhododendron in Wiktionary, the free dictionary.

Databases

Societies

Botanical gardens

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