Rhododendron arizelum Balf. f. & Forr.

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

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'Rhododendron arizelum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-arizelum/). Accessed 2020-05-28.

Genus

Synonyms

  • R. rex Levi, subsp. arizelum (Balf.f. & Forrest) D.F.Chamb.

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.
apex
(pl. apices) Tip. apical At the apex.
bloom
Bluish or greyish waxy substance on leaves or fruits.
glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
glandular
Bearing glands.
mucro
Short straight point. mucronate Bearing a mucro.
style
Generally an elongated structure arising from the ovary bearing the stigma at its tip.
taxon
(pl. taxa) Group of organisms sharing the same taxonomic rank (family genus species infraspecific variety).

References

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Credits

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

Recommended citation
'Rhododendron arizelum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-arizelum/). Accessed 2020-05-28.

Large shrub or more commonly a small tree, 2.5-12 m; bark rough. Leaves 12-21 x 4.5-11 cm, obovate, lower surface densely covered with a two-layered red-brown indumentum, the upper layer composed of strongly fimbriate cup-shaped hairs, the lower compacted; petioles terete. Flowers 12-20, in a tight truss, 7-8-lobed, yellow or cream to (more rarely) pink, with a basal blotch and flecks, obliquely to regularly campanulate, nectar pouches lacking, 30-45 mm; stamens 14-16; ovary densely brown-tomentose. Flowering April-May. Royal Horticultural Society (1997)

Distribution  Myanmar NE China SE Tibet, W Yunnan

Habitat 3,000-4,000 m

RHS Hardiness Rating H4

Awards AM 1963 (National Trust for Scotland, Brodick Castle Gardens) to a clone 'Brodick'; flowers Solferino Purple, with a crimson-black blotch. AM 1963 (Earl of Stair, Stranraer) to var. rubicosum; flowers Rose Red, with a more or less black blotch.

Conservation status Least concern (LC)

Taxonomic note (R. rex H.Lev. subsp. arizelum [Balf.f. & Forrest] D.F.Chamb.) Intermediates (possibly hybrids) between R. arizelum and R. rex subsp. fictolacteum, occur where the range of the two taxa meet. Forms, with pink (often relatively intense) flowers have been referred to var. rubicosum Cowan & Davidian. The status of this taxon in the wild is, however, uncertain. Royal Horticultural Society (1997)

An evergreen shrub or a small tree up to 20 ft high; young shoots, leaf-stalks, and undersurface of leaves covered with a velvety, cinnamon-brown felt, which is especially richly coloured beneath the leaves; these are obovate, tapered at the base, rounded at the apex, and with a short mucro there, 5 to 9 in. long by 112 to 312 in. wide; stalk 12 to 1 in. long. Flowers borne in April, crowded, fifteen to twenty-five together, in a truss 5 or 6 in. across, each on a downy stalk 1 to 112 in. long. Calyx very small. Corolla bell-shaped, 112 to 2 in. wide, eight-lobed, in colour either white, creamy yellow, or yellow tinged with rose, with a dark crimson blotch or streaks of crimson at the base. Ovary densely downy but not glandular; style glabrous. (s. Falconeri)

In the wild, R. arizelum often occurs with R. sinogrande though at higher altitudes, and the range of the two species is very similar – from the Salween westward through upper Burma to the eastern end of the Himalaya. Forrest’s sendings are from various localities along the divide between the Salween and the eastern Irrawaddy, from the Shweli-Salween divide in the south, where he first found it in 1917, to as far north as 28° 50′ N. Near the north-western end of its range it was found by Kingdon Ward in 1924 on the far (southern) side of the Doshong La. The most recent collections in the Himalaya are Ludlow and Sherriff’s 2753 from the upper Subansiri, not far east of the Bhutan frontier, and Cox and Hutchison 427, collected in 1965 in the same region but nearer to the plains of Assam.

In the wild R. arizelum is a gregarious species: ‘One cliff, which faced the cold east, was painted pink and yellow for 2000 ft with flowers of R. arizelum. Looking squarely at this cliff from the river, one saw about 250 acres of rhododendron blossom… . The trees stood touching one another, and there must have been fifty thousand of them in bloom together’ (Kingdon Ward, Plant Hunters Paradise, p. 206, referring to the Adung valley, a feeder of the Irrawaddy). The variation in flower-colour was also remarked on by Farrer: ‘Typically, its blossom is of a creamy white… . But I have seen it vary to citron and once even to apricot-yellow, while there is no end to its developments into the loveliest rosy shades’ (Gard. Chron., Vol. 69 (1921), p. 274, referring to plants on the Burma-Yunnan frontier). There is also variation in the size and form of the truss, some plants in cultivation having very poor, flat-topped trusses. However, even when its flowers disappoint, R. arizelum makes a fine specimen, striking both in leaf and bark. Of the young foliage of R. arizelum in the Mishmi Hills Kingdon Ward wrote: ‘In August the young leaves project like silver spears powdered with bronze-dust from amongst the tawny red and bottle green of the old leaves’ (Plant Hunting on the Edge of the World, p. 278).

R. arizelum is hardy in a sheltered place near London but, like all the big-leaved rhododendrons, it attains its greatest size in the Atlantic zone. An Award of Merit was given to a form with a globular truss of about twenty flowers, coloured Solferino Purple with a dark crimson blotch in the throat, shown from the National Trust Gardens, Brodick, Isle of Arran, April 9, 1963.

From the Supplement (Vol. V)

This becomes R. rex subsp. arizelum. See further under R. rex in this supplement.


var. rubicosum Cowan & Davidian

Under this name is distinguished a form with bright crimson flowers, raised by Lord Stair at Castle Kennedy, Wigtownshire, from Rock 59550. The seed was collected in 1923 on the slopes of Kenichunpu, Irrawaddy-Salween divide, just north of 28° N., at 12,000 ft. Award of Merit April 9, 1963.

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