Rhododendron hylaeum Balf. f. & Farrer

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Peter Norris, enabling the use of The Rhododendron Handbook 1998

Credits

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

Recommended citation
'Rhododendron hylaeum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-hylaeum/). Accessed 2024-09-10.

Genus

Rhododendron
Subsect. Thomsonia

Other taxa 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.
pome: Fleshy fruit with leathery core. Typical of Rosaceae subfamily Maloideae (e.g. Malus).
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.
campanulate: Bell-shaped.
cordate: Heart-shaped (i.e. with two equal lobes at the base).
glabrous: Lacking hairs smooth. glabrescent Becoming hairless.
glandular: Bearing glands.
key: (of fruit) Vernacular English term for winged samaras (as in e.g. Acer Fraxinus Ulmus)
oblanceolate: Inversely lanceolate; broadest towards apex.
obtuse: Blunt.
ovary: Lowest part of the carpel containing the ovules; later developing into the fruit.
petiole: Leaf stalk.
style: Generally an elongated structure arising from the ovary bearing the stigma at its tip.
undulate: Wavy.
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

Royal Horticultural Society (1997). The Rhododendron Handbook 1998

Credits

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

Recommended citation
'Rhododendron hylaeum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-hylaeum/). Accessed 2024-09-10.

A seedling of Rhododendron hylaeum with strongly red-pigmented new growth, sourced from the Himalayan Garden, Grwelthorpe, North Yorkshire, now at the Yorkshire Arboretum (May 2023). Image John Grimshaw.

Shrub or tree, 2.5–12 m; bark smooth, peeling; young shoots more or less glabrous. Leaves 8.5–14.5 × 3.3–5.7 cm, base rounded, upper surface glabrous, lower surface with epidermis greenish and lacking papillae, with scattered fasciculate hairs arising from red persistent hair bases on the veins, otherwise glabrous; petioles 1.5–2 cm, narrowly winged, stalked-glandular when young, soon glabrous. Flowers 10–12, in a dense truss; calyx 2–8 mm, cupular when well-developed; corolla fleshy, rose-pink, with dark flecks, tubular-campanulate, with nectar pouches; ovary and style glabrous. Flowering May. Royal Horticultural Society (1997)

Distribution Myanmar NE China SE Tibet

Habitat 2,700–3,700 m

RHS Hardiness Rating H5

Conservation status Vulnerable (VU)

Taxonomic note This species is allied to R. faucium (q.v.). Royal Horticultural Society (1997)

An evergreen shrub or tree, up to 40 ft high, with a pinkish, flaking bark. Leaves leathery, oblanceolate to obovate, rounded to obtuse at the apex, narrowed to a roundish or slightly cordate base, 3 to 7 in. long, 1 to 2 in. wide, glabrous on both sides; petiole up to 1 in. long. Flowers in a terminal cluster of ten to twelve; pedicels 3⁄8 to 5⁄8 in. long, eglandular. Calyx cup-like, undulate, up to 5⁄8 in. long. Corolla tubular-campanulate, five-lobed, fleshy, up to 13⁄4 in. long, pink, spotted, with five nectar-pouches at the base. Ovary eglandular (but see below); style glabrous. (s. and ss. Thomsonii)

R. hylaeum was discovered by Farrer in 1920 on the Chawchi pass, on the border between Burma and Yunnan, and was introduced by Forrest and by Kingdon Ward in 1924. Forrest’s seed was collected near the type-locality (F.24660), but the seed sent home by Kingdon Ward (KW 6401) was taken from a fruiting branch collected by one of his bearers near Pemakochung at the head of the Tsangpo gorge. It is also in cultivation from seeds collected in the Seinghku valley, north-west Burma (KW 6833).

R. hylaeum is an uncommon species, but is quite hardy south of London in a sheltered place. It is handsome in foliage and bark, but otherwise of no ornamental value. Although the ovary in R. hylaeum is said by Cowan and Davidian to be always eglandular, it is glandular in some cultivated plants, which would therefore come out in their key as R. eclecteum, some forms of which resemble R. hylaeum in flower, though the typical variety of R. eclecteum is very distinct from it in foliage.

From the Supplement (Vol. V)

It was remarked in the third paragraph on page 686 that some plants grown as R. hylaeum differ from the description in having glandular ovaries. These belong to the newly described species:

† R. faucium Chamberlain – Near to R. hylaeum but the leaves smaller, tapered at the base, petioles shorter and ovary glandular. The type is Ludlow, Sherriff and Elliot 12289, collected in Pome province, south-east Tibet (Rev. 2., pp. 421–2).

This was introduced from the type-area by Kingdon Ward (KW 6401). But the other number mentioned on page 686 (KW 6833) is R. hylaeum. Other introductions of R. faucium are L.S. & E. 12019, 12045 and 12208. (Notes Roy. Bot. Gard. Edin., Vol. 36, pp. 124–5 (1978)).

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