Rhododendron citriniflorum Balf.f. & Forrest

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Article from Bean's Trees and Shrubs Hardy in the British Isles

Recommended citation
'Rhododendron citriniflorum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-citriniflorum/). Accessed 2020-01-20.

Genus

Synonyms

  • R. chlanidotum Balf. f. & Forr.

Infraspecifics

Other species in genus

Glossary

calyx
(pl. calyces) Outer whorl of the perianth. Composed of several sepals.
corolla
The inner whorl of the perianth. Composed of free or united petals often showy.
ovary
Lowest part of the carpel containing the ovules; later developing into the fruit.
Tibet
Traditional English name for the formerly independent state known to its people as Bod now the Tibet (Xizang) Autonomous Region of the People’s Republic of China. The name Xizang is used in lists of Chinese provinces.
calyx
(pl. calyces) Outer whorl of the perianth. Composed of several sepals.
glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
glandular
Bearing glands.
indumentum
A covering of hairs or scales.
ovary
Lowest part of the carpel containing the ovules; later developing into the fruit.
style
Generally an elongated structure arising from the ovary bearing the stigma at its tip.
subspecies
(subsp.) Taxonomic rank for a group of organisms showing the principal characters of a species but with significant definable morphological differentiation. A subspecies occurs in populations that can occupy a distinct geographical range or habitat.
variety
(var.) Taxonomic rank (varietas) grouping variants of a species with relatively minor differentiation in a few characters but occurring as recognisable populations. Often loosely used for rare minor variants more usefully ranked as forms.

References

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Credits

Article from Bean's Trees and Shrubs Hardy in the British Isles

Recommended citation
'Rhododendron citriniflorum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-citriniflorum/). Accessed 2020-01-20.

Dwarf shrub, 0.2-1.5 m. Leaves 4-7.5 x 1.5-2.3 cm, obovate to elliptic, lower surface densely covered with a thick grey-brown tomentum composed of ramiform hairs; petioles often winged, glabrous or with a white floccose tomentum when mature. Flowers 2-6, in a tight truss; calyx 2-12 mm, when well-developed cupular; corolla not fleshy, yellow or orange to carmine, tubular-campanulate, with nectar pouches, 32-45 mm; ovary stalked-glandular, abruptly contracted into the glabrous style. Flowering April-May. Royal Horticultural Society (1997)

Distribution  China SE Tibet, NW Yunnan

Habitat 4,000-4,600 m

RHS Hardiness Rating H5

Conservation status Vulnerable (VU)

Taxonomic note R. citriniflorum hybridizes with R. sanguineum and probably also R. temenium (q.v.); from both it may be distinguished by its thick tomentose leaf indumentum. Royal Horticultural Society (1997)

A dwarf evergreen shrub 2 to 4 ft high, with obovate or oblong leaves tapering to the base, 112 to 312 in. long, 12 to 112 in. wide, densely clothed beneath with loose tawny wool. Flowers opening in April or early May in clusters of six to eight; stalks clad with tawny bristles. Calyx variable in size. Corolla typically clear, unspotted, lemon-yellow, but sometimes rose-coloured, or in intermediate shades, bell-shaped, 134 in. long, five-lobed. Stamens ten, downy at the base or glabrous. Ovary matted with tawny hairs and glandular bristly; style glabrous. (s. Neriiflorum ss. Sanguineum)

This variable species resembles R. sanguineum in the shape and texture of its leaves, but they differ markedly in their thick indumentum of matted hairs. It was described from specimens collected by Forrest on the Mekong-Salween divide, N.W. Yunnan, and introduced by him. Although the flowers were said in the original description to be lemon-yellow, the authors cite Forrest’s 14271, in which the flowers were described in the field note as ‘soft rose without markings’. The species also occurs in S.E. Tibet (Tsarong) on the Salween-Irrawaddy divide.

The following subspecies are placed under R. citriniflorum by Cowan (Notes R.B.G. Edin., Vol. 20, p. 75).

subsp. aureolum Cowan – Ovary without glands. Otherwise not differing from the type.

subsp. horaeum (Balf. f. & Forr.) Cowan R. horaeum Balf. f. & Forr. – Resembling the type in foliage, but flowers deep crimson. Ovary tomentose, without glands. Introduced by Forrest from S.E. Tibet (Tsarong), later by Rock. The subsp. rubens Cowan is the same, but the ovary is glandular as well as tomentose.

From the Supplement (Vol. V)

Dr Chamberlain provides a simpler treatment than Dr Cowan’s, recognising only one variety (not subspecies).

var. horaeum (Balf.f. & Forr.) Chamberlain R. horaeum Balf.f. & Forr.; R. citriniflorum subsp. horaeum (Balf.f. & Forr.) Cowan; R. c. subsp. aureolum Cowan – Flowers red or orange or in intermediate shades; calyx mostly 14 to 12 in. long; ovary and pedicels without glands (against flowers yellow, calyx shorter, ovary and pedicels usually glandular in the typical variety). However, Dr Chamberlain admits that intermediates occur, Cowan’s R. c. subsp. rubens being of this nature.

For natural hybrids, see Rev. 2., p. 393.


var. citriniflorum

Corolla yellow; calyx 2-5(-10)mm; ovary and usually pedicels stalked-glandular.

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