Rhododendron indicum (L.) Sweet

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

Recommended citation
'Rhododendron indicum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-indicum/). Accessed 2024-05-28.


Other taxa in genus


(pl. calyces) Outer whorl of the perianth. Composed of several sepals.
The inner whorl of the perianth. Composed of free or united petals often showy.
Lowest part of the carpel containing the ovules; later developing into the fruit.
Lying flat against an object.
Bluish or greyish waxy substance on leaves or fruits.
The inner whorl of the perianth. Composed of free or united petals often showy.
Lacking hairs smooth. glabrescent Becoming hairless.
Lance-shaped; broadest in middle tapering to point.
Inversely lanceolate; broadest towards apex.
Lying flat.
Generally an elongated structure arising from the ovary bearing the stigma at its tip.


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

Recommended citation
'Rhododendron indicum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhododendron/rhododendron-indicum/). Accessed 2024-05-28.

Much-branched shrub, usually low and prostrate though sometimes to 2 m; young shoots and petioles covered with adpressed flattened chestnut brown bristles. Leaves of two kinds; spring leaves deciduous, 2–3 × 0.8–1 cm, narrowly lanceolate to oblanceolate, apex acute, upper surface with scattered bristles, lower surface paler, with bristles restricted to midrib, summer leaves persistent, 1–1.8 × 0.3–0.5 cm. Pedicels covered with stiff brown hairs. Flowers 1–2 per inflorescence; calyx c.1 mm; corolla bright red to scarlet, occasionally rose-red, broadly funnel-shaped, 30–50 mm; stamens 5; ovary densely covered with adpressed shining brown hairs, style glabrous. Flowering June-July. Royal Horticultural Society (1997)

Distribution  Japan Honshu, Kyushu

Habitat 60–1,100 m

RHS Hardiness Rating H5

Awards AM 1975 (RHS Garden, Wisley) to a very free-flowering form, with flowers red speckled crimson.

Taxonomic note This is a widely cultivated species in its native Japan; selected forms are also to be found in gardens in Britain. It is closely allied to R. kaempferi (q.v.). Royal Horticultural Society (1997)

Azalea indica L.; A. macrantha Bunge; R. macranthum (Bunge) D. Don; R. indicum var. macranthum (Bunge) Maxim.; R. breynii Planch.; R. decumbens D. Don

An evergreen shrub, sometimes a dense bush from 3 to 6 ft high, sometimes low and more or less prostrate; young shoots slender, stiff, clothed with flattened, appressed, bristle-like hairs pointing towards the end of the branch. Leaves lanceolate to oblanceolate, tapered at the base, pointed, often sparsely toothed, 1 to 112 in. long, 14 to 34 in. wide; dark green and rather glossy above, paler beneath, with appressed red-brown bristles on both sides; stalk 112 to 18 in. long. Flowers opening in June, solitary or in pairs at the end of the shoot. Calyx and flower-stalk appressed-bristly. Corolla broadly funnel-shaped, about 112 in. long, rather more wide, five-lobed, bright red to scarlet, sometimes rosy red. Stamens five, about the same length as the corolla, slightly downy towards the base. Ovary covered with erect bristles; style glabrous.

Native of S. Japan; introduced in 1833 by a Mr M’Killigan to Knight’s nursery at Chelsea. It had long been cultivated by the Japanese, and Wilson, when in Japan, found that some two hundred sorts are recognised by them. Although it – or rather its varieties – held a place in European gardens for some years, it was rapidly displaced after the year 1850 by the Chinese species, R. simsii (q.v.), a species with many varieties also, somewhat more tender than R. indicum and better adapted for greenhouse cultivation, especially for forcing early into bloom. These two species and their varieties have been much confused by botanists and have usually been referred to collectively as “Indian Azaleas”, R. simsii is distinguished by its usually ten (sometimes eight) stamens to a flower. The true R. indicum is rare in gardens. Although not robust in habit, it and the following varieties are hardy there, and this cannot be said of R. simsii and its forms:


A miniature shrub usually only one foot or so high. Leaves {1/2} to 1 in. long, {1/8} to {1/6} in. wide, glossy green above, grey beneath, bristly on both surfaces. Flowers very double, salmon red, in the bud state very much resembling small rosebuds. It has lived in the open air at Kew for many years but grows slowly and prefers a rather warmer climate. Suitable for the rock garden. Introduced from Japan about 1877. It is perfectly hardy, but needs slight shade and moist soil. It has also been known as Azalea rosaeflora.


This has thicker leaves than the type and, bright rose flowers with wavy margins. Introduced by Fortune about 1850. Bot. Mag., t. 4726.


Corolla rich red, split to the base into narrow, strap-shaped segments nearly 1 in. long, {1/12} to {1/8} in. wide. Often the two or three upper segments are united half-way down. Calyx five-lobed, the lobes {1/8} in. long, bristly, pointed. Stamens five, red; style 1{1/4} in. long, red. It flowers in the open air at Kew in June, but can be regarded only as a curious monstrosity.

R eriocarpum (Hayata) Nakai

R. indicum var. eriocarpum Hayata
R. simsii var. eriocarpum (Hayata) Wils

Little seems to be known of this azalea, which is perhaps intermediate between R. indicum and R. simsii, and was described from a specimen collected on Kaganoshima, an island about 40 miles south-west of Yakushima at the northern end of the Ryukyus. No specimen has been seen, but according to Hayata the leaves are 1 in. long, obovate or obovate-oblong; inflorescences three- to four-flowered; stamens nine or ten. The colour of the flowers was not stated, but according to Wilson, who saw fresh specimens from neighbouring islands, they are white, pink, or rose-coloured. The plants cultivated as R. simsii var. eriocarpum – the so-called Gumpo azaleas – came from Japanese nurseries and therefore cannot be regarded as authentic; they are mentioned in the section on evergreen azalea hybrids, their taxonomic position being uncertain.R. eriocarpum appears to be in many respects similar to R. tamurae (Makino) Masamune, of Kyushu and Yakushima, for which see Ohwi’s Flora of Japan. The author of this work evidently considers that the plants described by Nakai, when raising Hayata’s variety to specific rank, are in fact R. tamurae, but that does not affect the validity of the combination R. eriocarpum (Hayata) Nakai, which is typified by Hayata’s original specimen and description. If in fact only one species is involved it would take the name R. eriocarpum.

R nakaharae Hayata

A low or prostrate shrub. Leaves oblong-elliptic or oblong-ovate, sometimes obliquely so, acute and apiculate at the apex, {1/2} to {3/4} in. long, {3/16} to {3/8} in. wide, rich glossy green above, paler beneath, appressed-bristly on both sides, especially on the margins and the midrib beneath. Flowers one to three in the truss. Calyx-lobes ovate or narrow-ovate, strigose on the outside and at the edges. Corolla deeply lobed, scarlet with a darker flare on the upper lobe, about 1{3/8} in. wide. Stamens six to ten; anthers purple. Native of the Tatun range in northern Formosa. This description is made from the clone named ‘Mariko’, which is of uncertain provenance. Owing to lack of herbarium material of the true R. nakaharai it is impossible to say whether it represents the true species, though it agrees quite well with published descriptions. It appears to be related to both R. simsii and R. indicum. ‘Mariko’ is a useful plant, as it is quite hardy and bears its showy flowers in late June or July. It is an ideal plant for the rock garden and stands full sun.


Flowers striped red and white. Introduced with the type in 1833 to Knight’s nursery at Chelsea, and a favourite variety for breeding from in the early days. Rather tender. In England it disappeared from cultivation, but a similar plant was later introduced from Japan under the name ‘Matushima’.R. indicum is known in Japan as the ‘Satsuki-tsutsuji’, or Fifth-month Azalea ‘from the fact that it blossoms in June, which is the fifth month of the year reckoning by the old Chinese calendar’ (Wilson). But the Satsuki group of azaleas, of which several hundred varieties have been named in Japan, are probably for the most parts hybrids of R. indicum with various other evergreen species; see further in the section on evergreen azalea hybrids.