Author

GP Jürgens

Ericaceae

Rhododendron campylocarpum x Rhododendron thomsonii

by GP Jürgens
Sikkim2004 404 P689
Sikkim/India Lachung 3400m May

Description

This plant is a natural hybrid between Rhododendron campylocarpum and Rhododendron thomsonii, both subalpine to alpine shrubs of the Eastern Himalaya whose ranges overlap broadly in Sikkim, Bhutan, eastern Nepal and southern Tibet. Because it is a hybrid rather than a described species, it carries no meaningful GBIF distribution of its own — the apparent global record set and the placeholder accepted name 'Plantae' reflect database artefacts, not a real occurrence pattern. Such intermediates arise wherever the two parents grow intermingled in mossy fir and Rhododendron forest and on open subalpine slopes. The photographed plant from Lachung in northern Sikkim, near 3400 m and flowering in May, lies squarely within the elevational overlap zone of about 3000-4000 m where natural hybridisation is frequent.

Morphologically the hybrid is intermediate between its parents. From R. thomsonii it tends to inherit smooth, often peeling, reddish bark, rounded to obovate-orbicular leaves glaucous beneath, and a calyx that is enlarged and cupular; from R. campylocarpum it derives a more campanulate corolla and a tendency toward yellow pigmentation. The resulting flowers are typically campanulate and pale yellow to creamy, frequently flushed or blotched pink to rose, borne in loose terminal trusses; the curved capsule shows the influence of campylocarpum (the 'curved-fruited' parent). Stamens number ten and the style is glabrous.

Both parents belong to Rhododendron subgenus Hymenanthes (the elepidote rhododendrons), and their hybrid swarms are a classic example of natural introgression, long noted in Sikkim by J. D. Hooker. These intermediates blur species limits in the field and are of horticultural importance, both parents being foundational in the breeding of yellow- and red-flowered garden hybrids.

Sources: POWO (Kew), GBIF, Flora of Bhutan, The Rhododendron Handbook (Royal Horticultural Society), Cox & Cox A Encyclopedia of Rhododendron Species, Hooker The Rhododendrons of Sikkim-Himalaya

Ericaceae

Rhododendron ciliatum

by GP Jürgens

Hook. f.

Bhutan2014 551
Bhutan Phobjika 2810, May
Bhutan2014 553
Bhutan Phobjika 2810, May
Bh2008 404 P634
Bhutan Phobjika, 3100m April
Bh2008 404 P634 scaled
Bhutan Phobjika, 3100m April
Nepal 1994 70 ergebnis
Ost-Nepal Jaljale Himal, 2800m April

Description

Rhododendron ciliatum is a low evergreen shrub of the Eastern Himalaya, with verified native occurrences in India, Nepal, Bhutan and China; numerous further GBIF records from Britain, North America, Austria, Italy, New Zealand and elsewhere reflect its wide cultivation. It grows on open hillsides, rocky slopes and forest margins, often epiphytically on mossy trunks, in the upper-temperate and subalpine zones between about 2700 and 3700 m. The cited material from Phobjika in Bhutan (2810-3100 m, April-May) and the Jaljale Himal of eastern Nepal (2800 m, April) shows the species in its characteristic early-spring flowering.

It forms a compact, rounded shrub usually under 1.5 m with peeling reddish-brown bark and bristly young shoots. The elliptic to oblong leaves are leathery and dark green, conspicuously fringed at the margins and on the midrib beneath with long stiff cilia, the feature giving the species its name, and scaly below. The flowers are borne in small terminal trusses of two to five; the corolla is broadly funnel-campanulate, white to pale pink, often deeper rose in bud, with a slightly nodding posture. The fruit is a small ovoid scaly capsule that splits to release abundant minute winged seeds.

Rhododendron ciliatum belongs to subgenus Rhododendron, subsection Maddenia, a lepidote (scaly) group, and was described by J.D. Hooker from his Sikkim collections; it has contributed extensively to horticultural hybridisation for its hardiness and early bloom. Ecologically it is an early-spring nectar source in the high forest. Widespread and locally common across its native range and abundant in cultivation, it is not regarded as threatened.

Author: Hook. f. · Sources: POWO (Kew), GBIF, Flora of Bhutan, The Genus Rhododendron (Royal Botanic Garden Edinburgh), Flora of China

Ericaceae

Rhododendron cinnabarinum

by GP Jürgens

Hook. f.

Bhutan2014 877
Bhutan Chele-La 2850m, May
Bhutan2014 882
Bhutan Chele-La 2850m, May
Bh2008 221 P349
Bhutan Tumching-La, 3400m April
Bh2008 222 G350
Bhutan Tumching-La, 3400m April
Sikkim2003 191 G262
Sikkim Dzongri 3900m 08.2003

Description

Rhododendron cinnabarinum is an Eastern Himalayan species native to Bhutan, Sikkim and adjacent northeastern India, Nepal and southern Tibet (China), the nearly 768 records also reflecting its popularity in cultivation in Britain, North America and elsewhere. It is a shrub of the cool temperate to subalpine zone, the images documenting plants on the Chele-La in Bhutan at about 2850 m in May, the Tumching-La at about 3400 m in April, and Dzongri in Sikkim near 3900 m. It grows in fir and mixed forest, rhododendron thickets, forest margins and open subalpine scrub on moist, acidic, humus-rich slopes within the monsoon-influenced humid belt of the range.

It is an evergreen shrub reaching one to several metres, with smooth bark and aromatic foliage. The leaves are elliptic to obovate, conspicuously glaucous-blue when young and densely scaly (lepidote) beneath, the scales being diagnostic of the lepidote rhododendrons. The pendulous, tubular-campanulate to narrowly funnel-shaped flowers are borne in small terminal trusses and are noted for their waxy texture and remarkable colour range, from cinnabar-red and orange to plum and yellow; the ten stamens and the style are enclosed within the elongate corolla tube, which matures into a scaly capsule.

Described by J.D. Hooker, the species is placed in subgenus Rhododendron, subsection Cinnabarina, the only members of the lepidote group with markedly tubular, drooping corollas suited to pollination by birds and long-tongued insects. It is variable across its range, with several recognised subspecies and varieties differing in flower colour and foliage, and is an important parent in horticulture. Locally common in suitable habitat and widely cultivated, it is not regarded as globally threatened, though parts of its native forest are under pressure.

Author: Hook. f. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, The Genus Rhododendron (Royal Botanic Garden Edinburgh)

Ericaceae

Rhododendron dalhousieae

by GP Jürgens

Hook. f.

Bh09 237 P397
Bhutan Wangdi 1950m, June
Bh09 238 G399
Bhutan Wangdi 1950m, June
Nepal 97 314 P620
Nepal Honggaon 2360m May
Nepal 97 418 P807
Nepal Taskigaon 3000m May
Sikkim 2006 172 ergebnis
Sikkim 2006 175 ergebnis
India West-Bengal, Samadan 2400m, May

Description

Rhododendron dalhousieae is an epiphytic or terrestrial shrub of the eastern Himalaya, distributed across India, Nepal, Bhutan and adjacent China; its c. 149 georeferenced records track the wet temperate forest belt (records from Britain and New Zealand reflect its long history in cultivation). It grows in humid broadleaf and Rhododendron-rich forest, often perched on mossy trunks and rocks or on steep banks, chiefly between 1800 and 3000 m. The image documents populations across its range, from Wangdi in Bhutan at 1950 m to Nepal's Honggaon and Taskigaon (2360-3000 m) and Samadan in West Bengal at 2400 m, flowering from May into June in the cloud-forest zone.

It is a straggling, sparsely branched shrub 1-3 m tall, frequently epiphytic, with peeling bark and large, obovate to elliptic leaves clustered toward the branch tips, glaucous beneath and bearing scattered scales. The flowers are among the most spectacular of Himalayan rhododendrons: borne in lax trusses of two to six, each broadly funnel-campanulate, 7-12 cm long, fragrant, white often flushed with pale yellow or pink, with a long tube. The ten stamens and slender style are enclosed within the corolla, and the scaly ovary matures into an elongate capsule splitting to release numerous minute winged seeds.

Described by Hooker f. (Hook. f.) from his Sikkim explorations, R. dalhousieae belongs to Rhododendron subgenus Rhododendron, section Rhododendron (the lepidote or scaly-leaved rhododendrons), and is named for Lady Dalhousie. Its large, fragrant, pale flowers suggest pollination by moths and large bees. Long prized in horticulture, it is widespread but locally uncommon and dependent on intact humid forest; habitat loss makes some populations vulnerable, though it is not formally threatened.

Author: Hook. f. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, Flora of Bhutan and Sikkim, The Genus Rhododendron monograph (Edinburgh, Ericaceae)

Ericaceae

Rhododendron dalhousieae var. rhabdotum

by GP Jürgens

(Balf. f. & R.E. Cooper) Cullen

Bhutan2014 305
Bhutan Tritangbi 2250m, May
Bhutan2014 308
Bhutan Tritangbi 2250m, May

Description

Rhododendron dalhousieae var. rhabdotum is a striking epiphytic rhododendron of the eastern Himalaya. GBIF records this taxon from Bhutan, India and China, with only around 16 occurrences, reflecting its restricted range in the moist temperate forests of the eastern Himalaya. It grows chiefly as an epiphyte on mossy trunks, or on cliffs and steep banks, in humid broadleaved and conifer forest, generally between about 2000 and 3000 m. The plant illustrated was photographed at Tritangbi in Bhutan at 2250 m in May, flowering in late spring within the cloud-forest belt where high humidity and abundant moss support its epiphytic habit.

It is a straggling, sparsely branched shrub with large, leathery, oblong-elliptic leaves clustered toward the branch tips. The flowers are borne in a loose terminal truss of a few very large, fragrant, broadly funnel-form to campanulate blooms 8-10 cm long. The corolla is creamy white to pale yellow, and the diagnostic feature distinguishing var. rhabdotum from typical R. dalhousieae is the presence of bold longitudinal red stripes running down the outside of the corolla tube (the epithet rhabdotum, striped). The fruit is a dry septicidal capsule releasing numerous minute winged seeds suited to dispersal onto epiphytic perches.

The taxon belongs to Rhododendron section Maddenia, a group of large-flowered, often epiphytic and fragrant species centred on the eastern Himalaya. Cullen treated rhabdotum as a variety of R. dalhousieae, a placement some authorities raise to species rank as R. rhabdotum. Its large fragrant flowers are adapted to moth pollination. With a narrow range, specialised epiphytic ecology and dependence on intact humid forest, it is vulnerable to deforestation and is a prized but localised eastern Himalayan rhododendron.

Author: (Balf. f. & R.E. Cooper) Cullen · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Annotated Checklist of the Flowering Plants of Nepal, The Genus Rhododendron: its classification and synonymy (Cullen, RBGE)

Ericaceae

Rhododendron delavayi

by GP Jürgens

Franch.

Bh2008 21 P38
Bhutan Thimphu-Chu, 2800m
Bh2008 23 P40
Bhutan Thimphu-Chu, 2800m

Description

Rhododendron delavayi Franch. is a shrub or small tree of the Sino-Himalayan region, distributed through south-western China (Yunnan, Guizhou, Sichuan, Xizang), Myanmar, Thailand, Vietnam, north-eastern India, Bhutan and Nepal, with horticultural records from the United Kingdom, United States, Canada and Belgium contributing to a GBIF total of around 1,290 occurrences. It grows in evergreen broadleaf forest, pine forest, open thickets and on rocky montane slopes, typically on acidic soils in the warm-temperate to lower montane belt. The illustrated plant comes from the Thimphu-Chu valley in Bhutan at about 2800 m, an elevation characteristic of the species where it forms a conspicuous element of the forest canopy and understorey and flowers in spring.

It is an evergreen shrub to small tree with stout branches and a thick, often flaking bark. The leaves are leathery, oblong-lanceolate to oblanceolate, dark green and glabrous above, the lower surface densely covered with a felted, persistent, fawn to greyish or whitish tomentum (indumentum) that is diagnostic of the species. The flowers are borne in dense, rounded, terminal trusses; each is broadly campanulate with a deep crimson to scarlet corolla of about five lobes, marked at the base with darker nectar pouches, and contains about ten stamens and a glabrous or hairy ovary with a long style. The fruit is a woody, cylindrical, ribbed capsule dehiscing by valves to release numerous minute seeds.

Rhododendron delavayi is the type species of subsection Arborea and is closely related to the Himalayan R. arboreum, with which it intergrades and shares the tree habit and red flowers; it is distinguished by its compact indumentum and floral details. Ecologically it is bird- and insect-pollinated and is a dominant component of warm broadleaf forest, while in cultivation it is valued as a parent of many hybrids. Although widespread, it is locally affected by deforestation and habitat conversion in parts of its range, but overall it remains common and is not regarded as globally threatened.

Author: Franch. · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, The Genus Rhododendron (Edinburgh, Chamberlain et al.)

Ericaceae

Rhododendron edgeworthii

by GP Jürgens

Hook. f.

Bhutan2014 315
Bhutan Tumching-La 2600m, May
Bhutan2014 317
Bhutan Tumching-La 2600m, May
Bh2008 159 P260
Bhutan Chendebji, 2600m April
Bh2008 160 P261
Bhutan Chendebji, 2600m April

Description

Rhododendron edgeworthii is distributed through the eastern Himalaya and adjacent montane south-west China, with native records spanning Bhutan, north-east India, Myanmar and Yunnan and Xizang (China); the remaining records among 665 georeferenced occurrences (United States, Canada, New Zealand, Britain, Belgium, Korea) reflect its long cultivation as an ornamental. It is characteristically epiphytic or saxicolous, growing on mossy tree trunks, boulders and humus-rich banks in cool, humid temperate forest with oak, Tsuga and other rhododendrons. The species was collected in Bhutan at Tumching-La and Chendebji at around 2600 m, consistent with its typical altitudinal range of roughly 2000-3700 m in the upper temperate zone.

It is a straggling, often epiphytic shrub to about 2-3 m, the young shoots and undersides of the leaves densely clothed in tawny, woolly-tomentose to setose indumentum. The leaves are elliptic to ovate, leathery, bullate-rugose above and conspicuously brown-felted beneath. The flowers, borne in lax trusses of two or three, are large, broadly funnelform-campanular, white usually flushed rose, and strongly fragrant, with the outer surface scaly and the lobes spreading; stamens are typically ten and the ovary densely scaly, ripening into a scaly capsule.

Within the genus the species belongs to subgenus Rhododendron (lepidote rhododendrons), section Rhododendron, subsection Edgeworthia, distinguished by the combination of bullate foliage, dense woolly indumentum and large scented blooms. It hybridises readily in cultivation and has contributed to fragrant hybrid groups. Though locally frequent across a wide range and assessed as of Least Concern, its dependence on undisturbed humid forest makes it sensitive to deforestation and collection pressure.

Author: Hook. f. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, The Rhododendron Handbook (Royal Horticultural Society), Cox & Cox The Encyclopedia of Rhododendron Species

Ericaceae

Rhododendron falconeri

by GP Jürgens

Hook.f.

Bhutan2014 349
Bhutan Tumching-La 3000m, May
Bh2008 100 P160
Bhutan Nabding, 2600m April
Bh2008 101 P161
Bhutan Nabding, 2600m April
Sikkim2004 24 P45
Sikkim West-Bengal, Sambon 1850m April
Sikkim2004 35 G61
Sikkim West-Bengal, Sambon 1850m April
Sikkim2004 31 P53 ergebnis
Sikkim Bersay 2810m, April

Description

Rhododendron falconeri is a large-leaved arborescent rhododendron native to the eastern Himalaya, occurring in Nepal, India (Sikkim, Darjeeling), Bhutan and adjacent China; the additional countries listed in GBIF (Great Britain, Canada, Belgium, Korea and others among 316 occurrences) reflect cultivated and herbarium records from botanic gardens. It grows in cool, humid temperate forest between roughly 2400 and 3300 m, forming a conspicuous component of the upper broadleaved and rhododendron-magnolia zone. The collection localities in the image caption, spanning Tumching-La and Nabding in Bhutan and Sambon and Bersay in Sikkim and West Bengal between 1850 and 3000 m in April and May, capture its flowering on misty ridge forests during the pre-monsoon.

The species is an evergreen shrub or small tree to 12 m with rough, flaking bark and stout shoots. Its very large obovate to elliptic leaves, up to 30 cm long, are dark green and rugose above and clothed beneath with a dense rusty to fawn indumentum of branched hairs, a diagnostic feature. The flowers are borne in dense rounded trusses of fifteen to twenty-five; each corolla is fleshy, campanulate, eight- to ten-lobed, creamy white to pale yellow and marked with a deep purple basal blotch. Fruit is a stout, curved, woody dehiscent capsule releasing numerous minute winged seeds.

Placed in subgenus Hymenanthes, subsection Falconera, R. falconeri is allied to R. hodgsonii and is among the most celebrated big-leaf rhododendrons, cultivated since its introduction by Hooker. The thick leaf indumentum and large foliage are adaptations to cool, fog-laden montane conditions, and it is pollinated chiefly by birds and large insects. While locally common and not globally threatened, Himalayan populations are pressured by fuelwood cutting, forest clearance and climate-driven upslope shifts.

Author: Hook.f. · Sources: POWO (Kew), GBIF, Flora of Bhutan, The Genus Rhododendron (Royal Botanic Garden Edinburgh), Hooker Rhododendrons of Sikkim-Himalaya

Ericaceae

Rhododendron fulgens

by GP Jürgens

Hook. f.

Sikkim2004 145 P253
Sikkim/India Singalila 4000m April
Sikkim2004 147 G255
Sikkim/India Singalila 4000m April
Nepal 97 213 P434
Nepal Thudam 3850m April

Description

Rhododendron fulgens is an East Himalayan shrub, with GBIF's c. 170 occurrences centred on India, Nepal, Bhutan and adjacent Tibetan China (records from GB, DE, US, CA, KR being cultivated material). It is a plant of the upper subalpine and lower alpine zones, typically 3300–4500 m, forming dense thickets at the treeline and in the understorey of Abies and Betula forest on moist, peaty, north-facing slopes. The populations photographed on the Singalila ridge (Sikkim/India) at 4000 m and at Thudam in eastern Nepal at 3850 m, both flowering in April, exemplify its preference for cool, snow-influenced ridges where it blooms before the monsoon.

It forms a stout, gnarled evergreen shrub to small tree 1–4 m tall, with smooth, peeling cinnamon to reddish-brown bark. The leaves are coriaceous, broadly elliptic to obovate, glossy dark green above and clothed beneath with a thick, persistent rusty to fulvous indumentum from which the epithet derives. The inflorescence is a compact, rounded truss of 10–20 campanulate flowers; the corolla is fleshy, deep blood-red to scarlet-crimson, about 2.5–3 cm long, with darker nectar pouches at the base. Stamens are 10, the ovary glandular, and the fruit a curved, woody, dehiscent capsule.

Described by J. D. Hooker from Sikkim, R. fulgens belongs to subsection Fulgensia within subgenus Hymenanthes and is allied to R. sherriffii and R. succothii. Though locally common across its core range and not globally threatened, its restricted treeline habitat is sensitive to grazing, fuelwood collection and shifting snowlines, and it serves as an important early-season nectar source for high-altitude pollinators.

Author: Hook. f. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, The Genus Rhododendron (Royal Horticultural Society monograph)

Ericaceae

Rhododendron glaucophyllum

by GP Jürgens

Rehder

Sikkim2004 392 P672
Sikkim (India), Lachung 3100 m
Sikkim2004 386 P664
Sikkim (India), Lachung 3100 m, May

Description

Rhododendron glaucophyllum is an Eastern Himalayan shrub distributed across Sikkim and adjacent India, Nepal, Bhutan and parts of south-western China and Myanmar. Its 172 GBIF records concentrate in this native range, the British, Canadian, New Zealand and United States points reflecting its long cultivation as an ornamental rhododendron. It grows in subalpine and alpine shrubberies, on open rocky slopes, cliffs, forest margins and moist banks, typically between about 2700 and 3700 m. The plant photographed at Lachung in Sikkim at 3100 m in May illustrates the species flowering in late spring within the cool, humid montane belt of the Eastern Himalaya.

It is a small, aromatic, evergreen shrub with peeling, papery bark and elliptic to oblong leaves that are dark green above and conspicuously glaucous and densely scaly (lepidote) beneath, the source of the epithet glaucophyllum. The flowers are borne in small terminal trusses; the campanulate corolla is pink to rose, sometimes paler or white, with the calyx well-developed and lobed, a distinctive feature of the species. Ten stamens and a lepidote ovary are typical of its subgenus. The fruit is a small, scaly, dehiscent capsule releasing numerous tiny seeds.

The species belongs to Rhododendron subgenus Rhododendron, section Rhododendron (the lepidote, scaly-leaved rhododendrons), and within it to the glaucophyllum group, characterised by aromatic foliage and a prominent calyx. Several varieties have been recognised across its range. Widely distributed and locally common, and well established in cultivation, R. glaucophyllum is not considered threatened, forming an attractive element of Eastern Himalayan subalpine scrub.

Author: Rehder · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, The Rhododendron Handbook (RHS)