Rhododendron williamsianum Rehd. & Wils.

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

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'Rhododendron williamsianum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-williamsianum/). Accessed 2020-08-12.

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.
bud
Immature shoot protected by scales that develops into leaves and/or flowers.
glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
glandular
Bearing glands.
glaucous
Grey-blue often from superficial layer of wax (bloom).
indumentum
A covering of hairs or scales.
orbicular
Circular.
ovary
Lowest part of the carpel containing the ovules; later developing into the fruit.
ovate
Egg-shaped; broadest towards the stem.
section
(sect.) Subdivision of a genus.
style
Generally an elongated structure arising from the ovary bearing the stigma at its tip.

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Credits

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

Recommended citation
'Rhododendron williamsianum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-williamsianum/). Accessed 2020-08-12.

A spreading dwarf shrub, 0.6-1.5 m; young shoots setose-glandular; young growth coppery-coloured. Leaves 2-4.5 x 1.4-3.5 cm, ovate-orbicular, base cordate, upper and lower surfaces glabrous though with red sessile glands below; petioles glabrous or setose-glandular. Flowers 2-3(-5) in a lax truss; calyx c.1 mm; corolla pale rose, with darker flecks, campanulate, lacking nectar pouches, 30-40 mm; ovary and style glandular. Flowering April-May. Royal Horticultural Society (1997)

Distribution  China Sichuan, Guizhou

Habitat 1,800-2,800 m

RHS Hardiness Rating H5

Conservation status Vulnerable (VU)

Taxonomic note This is a distinctive species without close allies that is local and rare in the wild. Royal Horticultural Society (1997)

An evergreen shrub up to 4 or 5 ft high, of rounded shape and usually wider than high, keeping close the ground, densely and intricately branched; young shoots slender, glaucous, thinly furnished with gland-tipped bristles. Leaves orbicular to ovate, usually heart-shaped at the base, 1 to 2 in. long, at first bronzy, finally dark green above, glaucous beneath; stalk 13 to 58 in. long, purplish when young, glandular-bristly. Flowers two to (rarely) four in a loose terminal cluster, opening in April. Calyx minute, glandular at the margin; flower-stalk 34 to 118 in. long, glandular. Corolla bell-shaped, 214 in. wide, soft rosy red, five-(rarely six-) lobed, the lobes notched; stamens ten, 114 in. long, glabrous; style overtopping the stamens and, like the ovary, sparsely set with stalked glands. Bot. Mag., t. 8935. (s. Thomsonii ss. Williamsianum)

Native of W. Szechwan, China; discovered and introduced by Wilson in 1908; he describes it as very local and occurring only in isolated thickets on the cliffs of Wa-Shan. It was later found on Mt Omei by Chinese botanists, growing in similar habitats. According to Fang, the plants there have rather larger leaves than in the typical form and up to fourteen stamens.

This species is named in honour of J. C. Williams of Caerhays and is one of the most distinct as well as beautiful of Chinese rhododendrons. It flowers when quite small, attracting notice then by the curiously disproportionate largeness of the flowers. It is quite hardy at Kew, but is slow-growing and dwarf. In more favoured gardens it makes dense hemispherical bushes not only attractive for its delicately coloured blossom but also for bronzy young foliage. Easily increased by late summer cuttings. It must be regarded as indispensable to any collection of rhododendrons. Its only fault is that both the flowers and the young growths are often killed by frost, but despite that it must be planted in an open, sunny position. Given the protection of a tree-canopy it does not set flower-bud and loses its characteristic shape.

R. williamsianum has proved to be a potent parent, imparting a compact habit and a short rounded leaf to its offspring in the most diverse crosses. All the hybrids between it and other species are charming, though some are inclined to be shy-flowering. Several crosses between R. williamsianum and Hardy Hybrids are now available, raised in Holland and Germany. See further in the section on hybrids.

From the Supplement (Vol. V)

† R. leishanicum Fang & S.S. Chang – A new species, described from a specimen collected in Kweichow in 1959. ‘This interesting new species is probably most closely allied to R. williamsianum, though with a dense indumentum on the petioles and the lower surface of the leaf midribs as in subsection Maculifera, that is however not as dendroid and matted as is usual in that subsection’ (Rev. 2, p. 261).

Seed of what will probably prove to be this species was collected in Kweichow by Simmons, Fliegner and Russell in September 1985.

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