Rhododendron roxieanum Forr.

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

Recommended citation
'Rhododendron roxieanum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-roxieanum/). Accessed 2020-03-31.

Genus

Synonyms

  • R. coccinopeplum Balf. f. & Forr.
  • R. cucullatum Hand.-Mazz.
  • R. poecilodermum Balf. f. & Forr.
  • R. recurvum Balf. f. & Forr.
  • R. aischropeplum 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.
apex
(pl. apices) Tip. apical At the apex.
bud
Immature shoot protected by scales that develops into leaves and/or flowers.
campanulate
Bell-shaped.
glandular
Bearing glands.
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.
linear
Strap-shaped.
midrib
midveinCentral and principal vein in a leaf.
oblanceolate
Inversely lanceolate; broadest towards apex.
petiole
Leaf stalk.
style
Generally an elongated structure arising from the ovary bearing the stigma at its tip.
tomentum
Dense layer of soft hairs. tomentose With tomentum.
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 roxieanum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-roxieanum/). Accessed 2020-03-31.

Shrub, sometimes dwarf, 0.15-2.5(-4) m. Leaves 5-12 x 0.6-4 cm, apex acute to cucullate, margins strongly recurved, lower surface covered with a thick two-layered indumentum, the upper layer rufous, loose, lanate-tomentose, composed of ramiform hairs, the lower radiate, compacted; petioles rufous-tomentose to glabrescent. Flowers 6-15, in tight truss; calyx 0.5-2 mm; corolla white to (rarely) pale yellow, sometimes flushed with pink, with purple flecks, funnel-campanulate, nectar pouches lacking; ovary densely rufous-tomentose and/or glandular, style glabrous. Flowering April-May. Royal Horticultural Society (1997)

Distribution  China SE Tibet, NW Yunnan, SW Sichuan

Habitat 3,050-4,250 m

RHS Hardiness Rating H5

Conservation status Least concern (LC)

Taxonomic note R. roxieanum hybridizes in the wild with R. proteoides and probably also with several other species, thus blurring the distinctions between the taxa. Var. oreonastes is a marked form with short, extremely narrow leaves. The variable var. cucullatum is morphologically intermediate between var. roxieanum and R. proteoides and is probably of hybrid origin. R. aganniphum, R. alutaceum and perhaps R. phaeochrysum may also be involved as parents in this hybrid complex. Royal Horticultural Society (1997)

A small evergreen shrub, usually under 6 ft high in the wild, but occasionally tree-like and up to 15 ft high; young shoots clothed with reddish-brown wool; inner bud-scales persisting on the branchlets for several years. Leaves linear, linear-oblong, or narrow-oblanceolate, 134 to 434 in. long, rarely over 1 in. wide and usually much less, pointed (more rarely blunt) at the apex, narrowed at the base to a stout petiole, which is tomentose like the young stems, upper surface of blade dark green, dull or glossy, midrib grooved, underside thickly covered with a reddish-brown or sometimes paler-coloured tomentum, concealing the raised midrib, margins usually recurved. Flowers ten to twenty in a tight terminal truss, opening in May; pedicels tomentose, with or without glands. Calyx very small, glandular and usually downy also. Corolla funnel-shaped to campanulate, 114 to 112 in. long, white or white flushed with pink or cream-coloured, with or without crimson spots. Stamens ten, hairy in the lower part. Ovary tomentose, with or without glands; style hairy at the base. Bot. Mag., t. 9383. (s. Taliense ss. Roxieanum)

A native of alpine and subalpine moorland or tree-line coniferous forest, from S.W. Szechwan through the bleaker parts of N.W. Yunnan to S.E. Tibet; discovered by Forrest in 1912 and introduced by him. It is a variable species, especially in habit and relative width of leaf, but curiously enough the taller forms are not broader-leaved as might be expected. Rock’s 59205 was described by him as a small tree 10 ft high but with linear, almost needle-shaped leaves. R. roxieanum is slow-growing, and also slow to reach the flowering state, but makes an interesting specimen.

From the Supplement (Vol. V)

[var. oreonastes] – This, not surprisingly, has been included in the typical part of R. roxieanum. If an Oreonastes group is to be recognised under the new provision of the Cultivar Code, it should perhaps be restricted to plants that are both narrow-leaved and of dwarf habit.

var. cucullatum (Hand.-Mazz.) Chamberlain R. cucullatum Hand.-Mazz. – To Handel-Mazzetti’s indignation, his species was sunk in R. roxieanum by Dr Hutchinson, but it has now been revived as a variety, differing essentially only in its broader leaves. There is, however, no sharp cut-off between it and var. roxieanum. It was recently collected in the Tali range (Cangshan) by the Sino-British Expedition of 1981, where it apparently intergrades with R. taliense (Cox, Rhododendrons 1981-2, p. 7; The Smaller Rhododendrons, p. 186)

R. recurvoides – This has now been transferred to subsect. Glischra.


R proteoides Balf. f. & W. W. Sm

Near to R. roxieanum, but with the leaves about half as long as in that species and blunt or rounded at the end; mostly they are under 2 in. long and {1/4} to {1/2} in. wide. The flowers in the type were yellow, but they may be creamy yellow or white. It is a dwarf shrub, usually under 2 ft high in the wild, and some plants found by Forrest were creeping and only 3 to 6 in. high. Most of his seed-collections were from the Mekong-Salween divide around Ka-kar-po at altitudes of 12,000 to 14,000 ft, but his F. 16609 was from the Muli region, S.W. Szechwan.

R recurvoides Tagg & Ward

Although resembling R. roxieanum in habit and aspect, this species is nevertheless very distinct in the glandular-bristly young stems, petioles, and outer bud-scales, and in the presence of stalked glands in the leaf-indumentum. It was discovered by Kingdon Ward in 1926 in the valley of the Dichu, a river which rises on the border between Tibet and Assam and flows west into the Lohit some miles south of the Tibetan town of Rima. He described it in his field note as a compact bushy shrub usually 2 to 3 ft high or less, flowering when quite small and growing on the sunniest side of steep granite screes among boulders. It is in cultivation from the seeds he collected in the type-locality and received an Award of Merit when shown by Col. E. Bolitho, Trengwainton, Cornwall, in 1941 on March 25. But April or May is its usual flowering-time.

var. cucullatum (Hand.-Mazz.) D.F.Chamb.

Leaves elliptic, 2.2-4× as long as broad; ovary and pedicels glandular and/or tomentose.

var. oreonastes (Balf.f. & Forrest) Davidian

Synonyms
R. recurvum var. oreonastes Balf. f. & Forr

Leaves linear, 8-15× as long as broad; ovary and pedicels glandular. Royal Horticultural Society (1997)

Awards
AM 1973 (Crown Estate Commissioners, Windsor); flowers white, corolla lobes tipped red-purple, with darker spots in throat. AGM 1993

RHS Hardiness Rating: H5

Leaves linear, less than {1/4} in. wide. Described from a plant only 2 ft high found by Forrest on the Kari La, Mekong-Yangtse divide, at 14,000 ft. It is not a very distinct variety, since taller forms may have very narrow leaves also (see above) and comparatively dwarf forms may have leaves of the normal width. Award of Merit May 1, 1973, when exhibited by the Crown Estate Commissioners, Windsor Great Park.

var. parvum Davidian

Either a synonym of R. proteoides or a hybrid of it (see under R. proteoides).

var. roxieanum

Leaves linear, 4-8× as long as broad; ovary and pedicels tomentose, with or without glands.

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