Rhododendron rupicola W. W. Sm.

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

Recommended citation
'Rhododendron rupicola' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-rupicola/). Accessed 2020-11-22.

Genus

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.
included
(botanical) Contained within another part or organ.
ovary
Lowest part of the carpel containing the ovules; later developing into the fruit.
apex
(pl. apices) Tip. apical At the apex.
calyx
(pl. calyces) Outer whorl of the perianth. Composed of several sepals.
glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
mucro
Short straight point. mucronate Bearing a mucro.
ovary
Lowest part of the carpel containing the ovules; later developing into the fruit.
ovate
Egg-shaped; broadest towards the stem.
style
Generally an elongated structure arising from the ovary bearing the stigma at its tip.
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.

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Credits

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

Recommended citation
'Rhododendron rupicola' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-rupicola/). Accessed 2020-11-22.

Much-branched dwarf shrub, to 0.6(-1.2) m. Leaves 0.7-2 x 0.3-1.3 cm, broadly elliptic to ovate, apex rounded, mucronate, lower surface covered with overlapping to slightly separated, predominantly dark brown (though with some amber to pale golden) scales. Flowers to 6 per inflorescence; calyx lobes 3-6 mm, oblong or broadly ovate, with a central band of scales; corolla usually an intense purple or yellow, occasionally deep crimson, magenta, or even white, broadly funnel-shaped, (8-)10-16(-18) mm; stamens 5-10, about as long as the corolla; ovary entirely pubescent or with scales on the upper half and a tuft of hairs at the apex, style longer than the stamens, glabrous or pubescent at base. Flowering April-May. Royal Horticultural Society (1997)

Distribution  Myanmar N China SE Tibet, W Yunnan, SW Sichuan

Habitat 3,000-4,875 m

RHS Hardiness Rating H6

Conservation status Least concern (LC)

An evergreen shrub 2 to 4 ft high, young shoots, leaves (on both sides), outside of calyx-lobes, ovary, and flower-stalks all very scaly. Leaves oval, often inclined to oblong, rounded but with a tiny mucro at the apex, 12 to 34 in. long, 16 to 13 in. wide, dark green above, yellowish grey between the scales beneath; stalk 112 to 18 in. long. Flowers opening in April and May in a terminal cluster of three to five, each on a very short stalk. Calyx 16 in. long, deeply five-lobed, the lobes oblong, deep purple, fringed at the margin. Corolla 78 in. wide, of a rich plum-purple, the tube very short and clothed inside with white hairs, five-lobed, the lobes ovate-oblong, rounded at the end, spreading, sprinkled more or less with scales outside, mostly up the middle. Stamens normally ten, but sometimes as few as seven, purple, 12 in. long, tufted with white down near the base; anthers pale brown. Ovary scaly towards the top; style overtopping the stamens, purple, glabrous. (s. Lapponicum)

Native of N.W. Yunnan and S.W. Szechwan at 12,000 to 14,000 ft; discovered by Forrest in 1910 in the Lichiang range and introduced by him in the same year. Its flowers, although small, are of a wonderfully rich purple, this colour extending to the style and the filaments of the stamens. R. russatum, which often bears flowers of a similar colour, differs in having much larger leaves and a downy style. R. rupicola is perfectly hardy.

From the Supplement (Vol. V)

var. chryseum (Balf.f. & Ward) Philipson & Philipson – See R. chryseum, page 629; also Davidian, The Rhododendron Species, Vol. 1, pp. 177-9 (as R. chryseum), where the forms in cultivation are discussed. The variety is variable in the number of stamens.

var. muliense (Balf.f. & Forr.) Philipson & Philipson R. muliense Balf.f. & Forr. – Considered in recent years to be synonymous with R. chryseum, R. muliense is recognised as a distinct variety of R. rupicola by the Philipsons, similar in flower-colour to var. chryseum, but having the calyx-lobes margined with both hairs and scales (against hairs only in var. chryseum and var. rupicola), and with the leaves often narrowly oblong rather than elliptic. The traditional method of distinguishing the two species, as they once were, namely five stamens in R. chryseum and ten in R. muliense, does not work, since var. chryseum varies in the number of its stamens, though it is the case that they are fairly consistently ten in var. muliense (Rev. Lapp., pp. 62-3).

[R. achroanthum] – Included in R. rupicola.


R achroanthum Balf. f. & W. W. Sm.

Synonyms
R. propinquum Balf. f. & Ward

This differs from R. rupicola in having five or six stamens only, and a more densely scaly ovary, but is probably not specifically distinct from it. It was introduced by Forrest in 1918 from the mountains north-east of Chungtien and is also in cultivation from seeds collected by Kingdon Ward in north-east upper Burma.

var. chryseum (Balf.f. & Kingdon-Ward) N.M.Philipson & Philipson

Synonyms
R. chryseum Balf.f. & Kingdon-Ward

Corolla yellow; calyx lobes margined with scales and hairs. Royal Horticultural Society (1997)

 

Distribution

  • Myanmar – NE
  • China – SE Tibet, NW Yunnan

RHS Hardiness Rating: H6


var. muliense (Balf.f. & Forrest) N.M.Philipson & Philipson.

Corolla yellow; calyx lobes margined with hairs only. Royal Horticultural Society (1997)

Distribution

  • China – SW Sichuan

This species is closely allied to R. russatum but may be distinguished by the presence of a central band of scales on the corolla lobes. It usually also has rather smaller leaves.


var. rupicola

Corolla purple to crimson, rarely white.

Distribution N Burma, China (SE Tibet, Yunnan, SW Sichuan).

Habitat to at least 4,000m.

Taxonomic note (incl. R. achroanthum Balf.f. & W.W.Sm)