Rhododendron rex Lévl.

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

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'Rhododendron rex' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-rex/). Accessed 2020-09-23.

Genus

Infraspecifics

Other species in genus

Glossary

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.
corolla
The inner whorl of the perianth. Composed of free or united petals often showy.
hybrid
Plant originating from the cross-fertilisation of genetically distinct individuals (e.g. two species or two subspecies).
indumentum
A covering of hairs or scales.
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 rex' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-rex/). Accessed 2020-09-23.

Large shrub or small tree, 2.5-12 m; bark rough; leaves 8-37 x 5.5-13.5 cm, obovate to oblanceolate; upper surface reticulate, lower surface covered with a dense fawn to rufous indumentum composed of slightly to moderately fimbriate cup-shaped hairs; petioles terete. Flowers 12-20, in a dense truss, fleshy, 7-8-lobed, white, with a crimson basal blotch and flecks, more or less regularly campanulate, nectar pouches lacking; stamens 14-16; ovary densely brown-tomentose. Flowering April-May. Royal Horticultural Society (1997)

Distribution  China Tibet, W Yunnan, S Sichuan

Habitat 3,000-4,000 m

RHS Hardiness Rating H5

Conservation status Least concern (LC)

See page 661, under R. fictolacteum. R. rex, in the former narrow sense, was often referred to by growers as a good form of R. fictolacteum, which had come into gardens many years earlier. But nomenclaturally R. rex is the senior species, of which R. fictolacteum now becomes a subspecies.

subsp. fictolacteum (Balf.f.) Chamberlain – This differs little from subsp. rex, the leading character of which is the fawn indumentum of the leaves, against brown or rust-coloured in subsp. fictolacteum (there is also a slight difference in the component hairs). The two subspecies intergrade, though the former has on the whole a more easterly distribution (Rev. 2, p. 255 and Map 76). In both the corolla is white, usually flushed with pink.

subsp. arizelum (Balf.f. & Forr.) Chamberlain – See R. arizelum, p. 601. The leading characters used in the Edinburgh revision to separate this from the preceding two subspecies are the pale yellow corolla and the relatively broader leaves. However, Dr Chamberlain remarks that many specimens collected in the wild, and belonging to R. rex sens. lat., cannot be referred with certainty to either subsp. arizelum or subsp. fictolacteum. Some of the undetermined specimens are intermediate between the two subspecies. Others have the yellow flowers of typical subsp. arizelum but the narrower leaves of subsp. fictolacteum; while others have white or pink flowers with the foliage of subsp. arizelum. To the latter category belongs the type of R. arizelum var. rubicosum Cowan & Davidian (see page 601). A number of the unplaceable specimens were collected in the region ranging from north-west Burma to south-east Tibet. In this connection it is of interest that Ludlow and Sherriff 1380 from the latter area, originally referred to R. arizelum, is determined in the Edinburgh revision as R. falconeri, and that Cox & Hutchison 427 from the Assam Himalaya, mentioned under R. arizelum on page 601, is now considered to be a possible hybrid of R. falconeri subsp. eximium.


subsp. fictolacteum (Balf.f.) D.F.Chamb.

Synonyms
R. fictolacteum Balf.f.

Leaf indumentum rufous to dark brown, composed of moderately fimbriate cup-shaped hairs.

Distribution China (W Yunnan, SE Tibet).

Habitat 3,000-4,000m.

Awards AM 1923 (G. Reuthe, Keston, Kent); flowers white, blotched crimson, with a few crimson spots. AM 1953 (Col. Lord Digby, Minterne, Dorset) to a clone ‘Cherry Tip’, as R. fictolacteum, from Rock 11385 ( USDA 59255); flowers white, margined pink, with a deep crimson blotch and numerous spots.

Taxonomic note (R. fictolacteum Balf.f.)

A variable subspecies in respect of the size of the leaves and the colour of the leaf indumentum; those forms with small leaves, 8-14cm long, and small flowers, have been referred to R. fictolacteum Balf.f. var. miniforme Davidian, here treated as a synonym of subsp. fictolacteum.

The morphological boundary between the two subspecies is not clear-cut. It does however seem that those plants that equate with subsp. rex, with a paler leaf indumentum and large leaves, occur in the NE of the distribution of the species. These are replaced by typical subsp. fictolacteum in the West. In parts of SE Tibet subsp. fictolacteum apparently hybridizes with R. arizelum to produce mixed populations in which it is not possible to assign some individuals to either taxon.


subsp. rex

Leaf indumentum fawn, composed of only slightly fimbriate cup-shaped hairs.

Distribution China (S Sichuan, NE Yunnan).

Habitat c.3,500m.

Awards AM 1946 (Lord Aberconway, Bodnant) to a clone ‘Roseum’, as R. fictolacteum var. roseum, from Kingdon-Ward 4509; flowers pale rose, with deeper coloured buds and with a small blotch. AM 1955 (Crown Estate AGM 1993, to a clone ‘Quartz’.

Commissioners, Windsor) to a clone ‘Quartz’, from Rock 18234 (USDA 3800); flowers pale pink, with a dull crimson blotch and spots.§FCC 1935 (J.J. Crosfield, Embley Park, Romsey) as R. fictolacteum, Ward’s var., from Kingdon-Ward 4509; flowers white, with a crimson blotch.

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