Rhododendron selense Franch.

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Credits

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

Recommended citation
'Rhododendron selense' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-selense/). Accessed 2020-01-17.

Genus

Synonyms

  • R. metrium Balf. f. & Forr.
  • R. nanothamnum Balf. f. & Forr.
  • R. axium Balf. f. & Forr.
  • R. chalarocladum Balf. f. & Forr.
  • R. dolerum 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.
cordate
Heart-shaped (i.e. with two equal lobes at the base).
glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
glandular
Bearing glands.
glaucous
Grey-blue often from superficial layer of wax (bloom).
hybrid
Plant originating from the cross-fertilisation of genetically distinct individuals (e.g. two species or two subspecies).
included
(botanical) Contained within another part or organ.
indumentum
A covering of hairs or scales.
obtuse
Blunt.
petiole
Leaf stalk.
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.

References

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Credits

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

Recommended citation
'Rhododendron selense' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-selense/). Accessed 2020-01-17.

Shrub or small tree, 1-5 m; young shoots and petioles stalked- to setose-glandular. Leaves 3.5-9 x 1.8-4 cm, ovate or obovate to elliptic, lower surface occasionally with a few persistent hairs towards the base otherwise glabrous. Flowers 3-8, in a lax truss; calyx 1-10 mm; corolla white or pale cream to deep pink, with or without purple flecks, funnel-campanulate, nectar pouches lacking, 25-40 mm; ovary densely stalked-glandular, style glabrous. Flowering April-May. Royal Horticultural Society (1997)

Distribution  China SE Tibet, NW Yunnan, SW Sichuan

Habitat 3,200-4,500 m

RHS Hardiness Rating H5

Conservation status Least concern (LC)

Taxonomic note R. selense is a variable species, the boundaries of which are ill-defined owing to widespread hybridization. Royal Horticultural Society (1997)

An evergreen shrub up to 10 ft high; branchlets slender, usually glandular, hairy or glabrous. Leaves oblong to oval or obovate, 1 to 312 in. long, 12 to 112 in. wide, rounded or obtuse at both ends, or sometimes slightly cordate at the base, dark green and glabrous or almost so above, underside paler and sometimes slightly glaucous, glabrous, or sometimes with a thin coating of hairs which often wears off by late summer; petiole up to 118 in. long. Flowers in terminal clusters of four to eight, opening in April or May; pedicels up to 118 in. long, glandular and sometimes hairy. Calyx up to 14 in. long, more or less glandular, sometimes hairy on the margin. Corolla between funnel-shaped and bell-shaped, 112 to 134 in. long and wide, five-lobed, varying in colour from white to various shades of rose, usually unspotted, but often with a crimson blotch at the base. Ovary densely glandular, sometimes slightly hairy also; style glabrous, sometimes slightly glandular at the base. (s. Thomsonii ss. Selense)

Native of N.W. Yunnan, bordering parts of S.E. Tibet, and of S.W. Szechwan; discovered by the French missionary Soulié on the Se La, Mekong-Salween divide, in 1895; introduced by Forrest from the same area in 1917. It is a somewhat variable species in shape and size of leaf, degree of glandularity, flower-colour, etc., and numerous species, now included in R. selense, were made out of its fluctuations. It is one of those species that is rarely seen in cultivation outside the gardens where it was raised from the wild seed. Growing by the thousand on its native mountainsides it must be a lovely sight when in flower, but the individual plant makes little display and is very slow to reach flowering age.

The following varieties are retained by Cowan and Davidian in their revision of the Thomsonii series;

From the Supplement (Vol. V)

The vars. pagophilum and probum are included in the typical subspecies of R. selense by Dr Chamberlain, while var. duseimatum is transferred to R. calvescens (not treated in the main work and probably not in cultivation).

subsp. dasycladum (Balf.f. & W.W. SM.) Chamberlain – Mentioned under R. selense on page 767 as a related species. Differing from subsp. selense in the young growths bearing long-stalked glands or glandular bristles, and longer calyx-lobes.

subsp. setiferum Balf.f. & Forr.) Chamberlain – Also mentioned under R. selense as a species. A character not mentioned is that the leaves have a more or less persistent though discontinuous indumentum beneath. Possibly a natural hybrid between R. selense subsp. selense and R. bainbridgeanum. (Rev. 2, p. 280).

subsp. jucundum (Balf.f. & W.W. Sm.) Chamberlain R. jucundum Balf.f. & W.W. Sm. – See Rev. 2, p. 280. Rare in cultivation and not mentioned in the main work.

R. × erythrocalyx Balf.f. & Forr. (as species) – This is considered by Dr Chamberlain to be a natural hybrid between R. selense and R. wardii, making swarms where the two species are in contact. Four of Balfour’s species founded on Forrest collections are here included in synonymy. A fifth – R. panteumorphum – mentioned under R. camplyocarpum on page 620, may also belong here (Rev. 2, pp. 280-81).


R dasycladum Balf. f. & W. W. Sm.

Synonyms
R. rhaibocarpum Balf. f. & W. W. Sm

This is nearly related to R. selense, but the young shoots and petioles are very bristly-glandular. The corolla is white, rose, or lilac-pink, with a crimson blotch at the base. It is usually a tall shrub in cultivation, and flowers quite freely. The deeper-coloured forms are attractive. It occurs wild within the area of R. selense.

R setiferum Balf. f. & Forr

Near to R. dasycladum, and with the same bristly-glandular branchlets and petioles, but with thick, leathery leaves. It was introduced by Forrest under F.14006 from the Salween-Mekong divide. The flowers are white, with crimson markings at the base.

subsp. dasycladum (Balf.f. & W.W.Sm.) D.F.Chamb.

Synonyms
R. dasycladum Balf.f. & W.W.Sm.
R. rhaibocarpum Balf.f. & W.W.Sm.

Young shoots with setose glands; leaves without a persistent indumentum beneath; longest calyx lobes 1-2(-5)mm.

Distribution China (W Yunnan, SW Sichuan).

Habitat 3,350-4,000m.

Subsp. dasycladum generally occurs at a lower altitude than does subsp. selense, even though the two do occur at the same localities. Subsp. dasycladum tends to have slightly larger leaves, darker pink flowers and a dense setose-glandular indumentum on the young shoots. However, there are intermediate forms that have in the past been referred to R. rhaibocarpum.

subsp. jucundum (Balf.f. & W.W.Sm.) D.F.Chamb.

Synonyms
R. jucundum Balf.f. & W.W.Sm.

Young shoots with long-stalked glands; leaves glabrous and glaucous beneath; longest calyx lobes (2-)4-6mm.

Distribution China (W Yunnan - Dali).

Habitat 3,200-3,900m.

This subspecies has a very restricted distribution.

subsp. selense

Young shoots with shortly stalked glands; leaves without a persistent indumentum and with a non-glaucous epidermis beneath; longest calyx lobes 2(-5)mm.

Distribution China (NW Yunnan, SW Sichuan).

Habitat 3,350-4,550m.

The naturally occurring hybrid between subsp. selense and R. wardii is grown as R. x erythrocalyx. This subspecies also hybridizes in the wild with R. eclecteum (q.v.), and probably also with subsp. dasycladum and R. vernicosum

subsp. setiferum (Balf.f. & Forrest) D.F.Chamb.

Synonyms
R. setiferum Balf.f. & Forrest
R. vestitum Tagg & Forrest

Young shoots with setose glands, leaves with a persistent or discontinuous indumentum beneath; longest calyx lobes (2-)4-10mm.

Distribution China (SE Tibet, NW Yunnan).

Habitat 3,650-4,500m.

Intermediate between subsp. selense and R. bainbridgeanum, and possibly of hybrid origin.

var. duseimatum (Balf. f. & Forr.) Cowan & Davidian

Synonyms
R. duseimatum Balf. f. & Forr

Ovary tomentose. Leaves oblong-lanceloate, 3 to 4 in. long.

var. pagophilum (Balf. f. & Ward) Cowan & Davidian

Synonyms
R. pagophilum Balf. f. & Ward

This name is retained by Cowan and Davidian for plants with small elliptic leaves and small flowers (usually dark rose to crimson in colour). In the type, the leaves were about 2 in. long and 1{1/8} in. wide.

var. probum (Balf. f. & Forr.) Cowan & Davidian

Synonyms
R. probum Balf. f. & Forr

A form with white, unmarked flowers.

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