Rhododendron erosum Cowan

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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 erosum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-erosum/). Accessed 2024-12-02.

Genus

Rhododendron
Subsect. Barbata

Infraspecifics

R exasperatum

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.
inflorescence: Flower-bearing part of a plant; arrangement of flowers on the floral axis.
ovary: Lowest part of the carpel containing the ovules; later developing into the fruit.
apex: (pl. apices) Tip. apical At the apex.
bud: Immature shoot protected by scales that develops into leaves and/or flowers.
campanulate: Bell-shaped.
glabrous: Lacking hairs smooth. glabrescent Becoming hairless.
glandular: Bearing glands.
indumentum: A covering of hairs or scales.
obtuse: Blunt.
petiole: Leaf stalk.
style: Generally an elongated structure arising from the ovary bearing the stigma at its tip.
umbel: Inflorescence in which pedicels all arise from same point on peduncle. May be flat-topped (as in e.g. Umbelliferae) to spherical (as in e.g. Araliaceae). umbellate In form of umbel.

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 erosum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-erosum/). Accessed 2024-12-02.

Developing new growth on Rhododendron erosum L&S 2755 (Yorkshire Arboretum, UK, May 2021). Image John Grimshaw.

Large shrub or small tree, 3.5–6.5 m; bark smooth and flaking, reddish brown; young shoots and petioles with long stiff bristles. Leaves 8–12.5 × 3.5–6.5 cm, broadly elliptic to oblong, apex rounded, apiculate, base cordate, upper surface with strongly impressed veins, lower surface with a floccose dendroid indumentum. Flowers fleshy, 10–15, in a tight truss, crimson to blood-red, with darker nectar pouches, tubular-campanulate, 30–35 mm; ovary densely stalked-glandular, style glabrous. Flowering March-April. Royal Horticultural Society (1997).

Distribution China SE Tibet

Habitat 3,000–3,800 m

RHS Hardiness Rating H5

Conservation status Vulnerable (VU)

Taxonomic note R. erosum is the most easterly of a complex of three closely allied species, also including R. barbatum and R. argipeplum. Some cultivated plants of this species have been called R. argipeplum, but it may be distinguished from that species by the relatively broader (1.5–2× as long as broad) and more rounded leaves. Royal Horticultural Society (1997)

An evergreen shrub or small tree, up to 30 ft high; branchlets slender, clad with stalked glands; bud-scales deciduous. Leaves leathery, oval, oblong-oval, obovate, obtuse to broadly rounded at the apex, rounded to subcordate at the base, up to 61⁄2 in. long and 33⁄4 in. wide, clad beneath with a woolly greyish or light brown indumentum which gradually wears away; petiole glandular-bristly, up to 3⁄4 in. long. Inflorescence a terminal umbel of twelve to fifteen flowers, opening in March or April; pedicels about 3⁄8 in. long, glandular. Calyx cup-shaped, pink, with short, irregular, gland-fringed lobes. Corolla five-lobed, funnel-campanulate, deep crimson or deep rosy pink, about 11⁄2 in. wide. Ovary densely covered with stalked glands; style glabrous. (s. Barbatum ss. Glischrum)

A native of the eastern Himalaya, found by Ludlow and Sherriff in 1936 on the Tibetan side of the range (Chayul and Tsari) at 10,000 to 12,000 ft, and introduced by them. Although not so fine in flower as R. barbatum, which it somewhat resembles, it has striking foliage.

Foliage of Rhododendron erosum Cooper 4115 at Deer Dell, Surrey, UK. Introduced as R. argipeplum, this taxon is considered distinct on account of its broader, rounder, more rugose leaves and bright red bud scales. Image John McQuire.

Young growth of Rhododendron erosum Cooper 4115 at Deer Dell, Surrey, UK, with conspicuous bright red bud scales. Image John McQuire.

R exasperatum Tagg

This species resembles R. erosum in its broad leaves, rounded at the apex, but their undersurface is glandular bristly (not woolly, later glabrous, as in R. erosum), and the foliage bud-scales are persistent. R. exasperatum was introduced by Kingdon Ward in 1926 from the Seinghku valley in north-west Burma, where it grows at 10,000 ft ‘only in the tanglewood on precipitous broken rock faces, where water drips continuously and everything is moss bound’. From there it ranges west through the Delei valley to the eastern end of the Himalaya, where it was found on several occasions by Ludlow and Sherriff and their companions. It is rather more tender than R. erosum and less attractive in its flowers (which, at least in the Kingdon Ward forms, are brick-red with an orange flush). The young growths are richly tinted.

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