Rhododendron pentaphyllum Maxim.

Sponsor

Kindly sponsored by
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 pentaphyllum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-pentaphyllum/). Accessed 2024-10-06.

Genus

Rhododendron
Sect. Sciadorhodion

Synonyms

Rhododendron pentaphyllum var. nikoense Komatsu
Rhododendron nikoense (Komatsu) Nakai
Rhododendron quinquefolium var. roseum Rehd.

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.
bloom: Bluish or greyish waxy substance on leaves or fruits.
bud: Immature shoot protected by scales that develops into leaves and/or flowers.
ciliate: Fringed with long hairs.
glabrous: Lacking hairs smooth. glabrescent Becoming hairless.
glandular: Bearing glands.
lanceolate: Lance-shaped; broadest in middle tapering to point.
midrib: midveinCentral and principal vein in a leaf.
ovary: Lowest part of the carpel containing the ovules; later developing into the fruit.
style: Generally an elongated structure arising from the ovary bearing the stigma at its tip.
whorl: Arrangement of three or more organs (leaves flowers) around a central axis. whorled Arranged in a whorl.

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 pentaphyllum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-pentaphyllum/). Accessed 2024-10-06.

Rhododendron pentaphyllum is perhaps the most exquisite of the spring-flowering deciduous azaleas, although very rare in cultivation on account of being difficult to please. Photographed at Deer Dell, Surrey, Image John McQuire.

Deciduous shrub or small tree, to 4(–8) m; vegetative shoots arising from buds in the axils of the previous year’s leaves; young twigs glabrous or sparsely covered with eglandular and gland-tipped hairs. Leaves turning red in autumn, arranged in pseudowhorls of 5(–7) at the apices of the branches, 2.1–6.3 × 1.1–3.8 cm, elliptic to obovate, apex acuminate to acute, base cuneate, lower surface glabrous to very sparsely unicellular-pubescent towards base, veins and midrib sometimes covered with straight or crisped eglandular or glandular hairs. Pedicels glabrous or covered with gland-tipped hairs. Flowers fragrant, appearing before or with the leaves, 1–2, in a contracted raceme; calyx 0.5–5 mm; corolla pink to deep rose, usually with red-brown flecks on upper three lobes, rotate-campanulate, the short tube gradually expanding into the longer limb, 15–35 mm. Capsule glabrous. Flowering March-April. Royal Horticultural Society (1997)

Distribution Japan Honshu, Shikoku, Kyushu

Habitat 500–1,700 m

RHS Hardiness Rating H4

Awards AM 1942 (Lord Aberconway, Bodnant); flowers Rose Bengal, paler with age.

Conservation status Least concern (LC)

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

A deciduous, sometimes tree-like azalea up to 20 ft high; young shoots often in tiers, thinly hairy when young, red-brown, becoming grey the second season. Leaves produced in a whorl of five at the end of the shoot, oval to oval-lanceolate, pointed, wedge-shaped at the base, 11⁄4 to 21⁄2 in. long, half as much wide, midrib downy on both surfaces, margins toothed and ciliate; stalk 1⁄8 to 1⁄3 in. long, thinly glandular-hairy. Flowers terminal, opening in April or May, solitary or in pairs; flower-stalk 1⁄2 in. long, varying from densely glandular to quite glabrous. Calyx with five triangular teeth 1⁄5 in. or less long. Corolla bright rose-pink, not spotted, 2 in. wide, with five spreading, rounded, often notched lobes. Stamens ten, of unequal length, downy at the base; anthers yellow; ovary and style glabrous. (s. Azalea ss. Canadense)

Native of central and southern Japan, where it grows in woodland, and is fond of partial shade. Wilson, who saw it wild in the Nikko region, wrote highly of its beauty both in bloom and in autumn, when the leaves change to rich orange and crimson.

In its foliage it resembles R. quinquefolium, but that species has white flowers, and produces its flowers and leafy shoots from the same bud, whereas in R. pentaphyllum they come from separate buds. It is rather slow to flower and prefers a sheltered place in moist leafy soil.

R. pentaphyllum received an Award of Merit on April 14, 1942, when shown by Lord Aberconway, Bodnant.

Despite its incredible beauty in flower, Rhododendron pentaphyllum is not unlike the closely related R. quinquefolium in having its flower buds and young growth susceptible to damage from spring frosts. Appropriate siting is critical in getting both species to perform. Image John McQuire.

Not unlike a Magnolia in overall effect, a well-grown Rhododendron pentaphyllum is a stunning sight in spring. Deer Dell, Surrey, UK. Image John McQuire.

Detail of the flowers of Rhododendron pentaphyllum at Deer Dell, Surrey, UK. Image John McQuire.

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