Tag:

Spring

Ericaceae

Rhododendron niveum

by GP Jürgens

Hook. f.

Sikkim2003 473 P655
Sikkim Lachung Valley 3100m August
Sikkim2004 409 P699
Sikkim Lachung Valley 3500m May
Sikkim2004 407 P697
Sikkim Lachung Valley 350

Description

Rhododendron niveum is a narrowly distributed eastern Himalayan species native to the Sikkim region of India, with extensions into adjacent China and Bhutan; its 92 georeferenced records, supplemented by occurrences in cultivation in Britain, Sweden, North America and Canada, reflect both a restricted wild range and its prominence in horticulture. It is a shrub or small tree of subalpine forest, rhododendron thickets and open hillsides near the treeline. The populations documented in the Lachung Valley of northern Sikkim between about 3100 and 3500 m, flowering in May and persisting in August, exemplify its high-montane habitat on cool, moist, acidic slopes.

The plant forms a compact tree or large shrub with stout branches. The leaves are obovate-elliptic, leathery and dark green above, their lower surface coated with a dense, persistent, silvery-white to fawn indumentum, the snowy tomentum that gives the species its epithet niveum. The flowers are grouped in dense, rounded terminal trusses; the campanulate corolla is a distinctive smoky lilac to deep purplish-mauve, a colour unusual among Himalayan rhododendrons, with ten stamens and a smooth, elongate ovary. The fruit is a woody, septicidal capsule releasing numerous minute seeds.

Within the vast genus Rhododendron, R. niveum belongs to subsection Arborea and is prized horticulturally for its striking flower colour and felted foliage, having been introduced by J. D. Hooker. Its restricted distribution and dependence on a narrow subalpine belt render it locally vulnerable to habitat loss, grazing and climatic shifts at the treeline, and it is of conservation interest as an eastern Himalayan near-endemic.

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

Ericaceae

Rhododendron pendulum

by GP Jürgens

Hook. f.

Bhutan2014 338
Bhutan Tumching-La 3000m, May
Bh2008 236 P373
Bhutan Tumching-La, 3500m April

Description

Rhododendron pendulum is an epiphytic or epilithic dwarf shrub of the humid Eastern Himalaya, with verified occurrences in China, India, Bhutan and Nepal (further GBIF records from Britain and the United States represent cultivated stock). It is most characteristic of cool, mist-laden temperate forest, where it perches on mossy trunks, branches and rock faces, generally between about 2700 and 3700 m. The Bhutanese material illustrated, from the Tumching-La between roughly 3000 and 3500 m in April and May, captures the species in flower at the close of the cold season in its typical cloud-forest setting.

It is a small, straggling shrub with thin, often pendulous branches densely clothed, like the young growth and leaf undersides, in a soft rusty-brown woolly indumentum. The small, elliptic to oblong leaves are leathery, with revolute margins, dark green and somewhat rugose above and thickly tawny-tomentose beneath. The flowers are borne few together at the branch tips; the corolla is broadly campanulate to rotate, white sometimes flushed pink, and comparatively large for so diminutive a plant. The fruit is a small ovoid capsule that splits septicidally to shed numerous minute seeds adapted to dispersal in the canopy.

Rhododendron pendulum belongs to subgenus Rhododendron, section Pogonanthum and its allies, distinguished by its woolly indumentum and epiphytic habit, and was described by J.D. Hooker from his Sikkim explorations. Its dependence on permanently humid, moss-rich forest makes it a sensitive indicator of intact cloud-forest conditions, and although not presently regarded as threatened, it is vulnerable to forest degradation and to disruption of the orographic mist regime on which its epiphytic lifestyle depends.

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

Ericaceae

Rhododendron poluninii

by GP Jürgens

Davidian

Bh2008 230 G365
Bhutan Tumching-La, 3400m April
Bh2008 231 P366
Bhutan Tumching-La, 3800m April

Description

Rhododendron poluninii Davidian is a narrowly distributed eastern Himalayan shrub known principally from Bhutan and the adjacent ranges of the Indo-Tibetan border. It is documented from Tumching-La in Bhutan between 3400 and 3800 m, flowering in April, within the cool temperate to subalpine forest belt. The species grows on humus-rich, acidic slopes among mixed conifer and broadleaved woodland, in rhododendron thickets and along forest margins where ample atmospheric moisture from the monsoon and frequent cloud cover prevail. With a single GBIF record and no aggregated country list, it is among the rarer and most poorly documented members of the genus, reflecting both its localised range and limited botanical collecting in the region.

It is a small to medium evergreen shrub with stiff branchlets clothed, like the undersides of the leaves, in a dense indumentum of scales or hairs typical of its alliance. The leaves are coriaceous, elliptic to oblong, dark green and lustrous above and paler or rusty beneath. The flowers are borne in compact terminal trusses, each with a campanulate to funnel-shaped corolla in shades of rose-pink to pale magenta, five-lobed, subtended by deciduous bud scales; the stamens are ten and the ovary surmounted by a slender style. The fruit is a woody, septicidal capsule releasing numerous minute seeds.

Described by the Rhododendron specialist H. H. Davidian, R. poluninii commemorates the collector Oleg Polunin and belongs to the vast genus Rhododendron, the dominant element of Himalayan subalpine vegetation. Its extreme rarity in collections and apparently restricted range suggest it may warrant priority survey and assessment, as such narrow endemics are especially exposed to habitat disturbance, forest clearance and climatic warming of the subalpine zone.

Author: Davidian · Sources: POWO (Kew), GBIF, Flora of Bhutan, The Rhododendron Species (Davidian), Edinburgh Rhododendron monograph (Cullen & Chamberlain)

Ericaceae

Rhododendron succothii

by GP Jürgens

Davidian

Bh2008 243 P383
Bhutan Tumching-La, 3800m April
Bh2008 250 P395
Bhutan Tumching-La, 3800m April
Bh2008 251 P397 1
Bhutan Tumching-La, 3800m April

Description

Rhododendron succothii is an eastern Himalayan rhododendron with a narrow native range centred on Bhutan and the adjacent Indian Himalaya (Arunachal Pradesh), the roughly sixty-five GBIF records (with cultivated entries from Canada and Britain) reflecting both its restricted distribution and its presence in specialist collections. It grows in temperate rhododendron and conifer forest, on forest margins and open rocky slopes, generally around 3000 to 4000 m. The photographed plant from the Tumching-La in Bhutan at 3800 m, flowering in April, exemplifies its early-spring flowering in the upper temperate forest belt where it forms part of the dense montane rhododendron thickets.

The species is an evergreen shrub or small tree with stout, glabrous branchlets. The leaves are coriaceous, broadly obovate to broadly elliptic with a rounded to retuse and apiculate apex, glabrous and glaucous beneath, the venation impressed above and prominent below. The flowers are borne in compact terminal trusses; the corolla is tubular-campanulate and fleshy, deep crimson to blood-red, with five lobes and dark nectar pouches at the base, and the stamens are typically ten with a glabrous ovary and stout style. The fruit is a woody, cylindrical, curved capsule dehiscing to release numerous small seeds.

Rhododendron succothii is an accepted species placed in subgenus Hymenanthes (the elepidote rhododendrons) within Rhododendron (Ericaceae), allied to the red-flowered Himalayan species. Its glaucous foliage, fleshy crimson corollas and early flowering reflect adaptation to cool, humid temperate forest and bird pollination. Given its narrow eastern Himalayan range and habitat dependence, the species is of conservation interest and merits monitoring against forest disturbance.

Author: Davidian · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, Cullen & Chamberlain revision of genus Rhododendron (Ericaceae monograph)

Ericaceae

Rhododendron thomsonii

by GP Jürgens

Hook. f.

Bhutan2014 631
Bhutan Phobjika 2800m, May
Bhutan2014 632
Bhutan Phobjika 2800m, May
Bhutan2014 382
Bhutan Tongsa 2000m, May
Sikkim2004 307 P542
Sikkim/India May

Description

Rhododendron thomsonii is an Eastern Himalayan endemic centred on Sikkim, Bhutan, adjacent northeastern India, southern Tibet (China) and easternmost Nepal, with the nearly 479 records also reflecting widespread cultivation in Britain, North America and continental Europe. In its native range it occupies the cool, humid temperate forest zone, the images documenting plants at Phobjika around 2800 m and Tongsa near 2000 m in Bhutan, flowering in May, together with material from Sikkim. It grows in fir and mixed broadleaved forest, on forest margins, in rhododendron thickets and on open rocky slopes between roughly 3000 and 4000 m, often where the monsoon brings high atmospheric humidity.

It is an evergreen shrub or small tree reaching several metres, with smooth, flaking reddish-brown to plum bark. The leaves are broadly obovate to orbicular, glabrous, glaucous beneath, rounded or emarginate at the apex and cordate at the base, borne on short petioles. The inflorescence is a loose terminal truss of few flowers; the corolla is fleshy, broadly campanulate and a deep blood-red to crimson, subtended by a large, cup-shaped, persistent and conspicuously coloured calyx that is diagnostic for the species. Stamens are ten; the ovary and curved style are glabrous, maturing into a woody capsule.

The species was described by J.D. Hooker from his Sikkim Himalayan expeditions and is the type of subsection Thomsonia within Rhododendron subgenus Hymenanthes. Its large fleshy calyx, glaucous foliage and waxy red bells distinguish it from related taxa and have made it a foundation species in horticultural breeding. Though restricted in distribution, it is locally common within suitable montane forest and is buffered by extensive cultivation, so it is not regarded as globally threatened, although habitat pressures affect parts of its native range.

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

Ericaceae

Rhododendron triflorum

by GP Jürgens

Hook. f.

Bhutan2014 357
Bhutan Tumching-La 3100m, May
Bhutan2014 402
Bhutan Yatong-La 2900m, May
Bhutan2014 403
Bhutan Yatong-La 2900m, May

Description

Rhododendron triflorum is an eastern Himalayan rhododendron distributed across China, Bhutan, India, Nepal and Myanmar, with about 484 GBIF occurrences (additional records abroad reflecting its popularity in cultivation). It grows in temperate forest, forest margins, rhododendron and conifer thickets and open shrubby slopes, generally between roughly 2700 and 3700 m. The plants photographed at Tumching-La (about 3100 m) and Yatong-La (about 2900 m) in Bhutan, both in May, exemplify its mid-montane forest habitat, where it flowers in late spring among mixed broad-leaved and coniferous woodland.

The species is an erect shrub or small tree with smooth, attractive coppery to reddish-brown, peeling bark. The leaves are evergreen, ovate to elliptic, glabrous above and conspicuously scaly (lepidote) beneath, the scales characteristic of the lepidote rhododendrons. The flowers are borne in small terminal clusters, typically in threes as the epithet triflorum indicates; the broadly funnel-campanulate corolla is pale yellow, often flushed or spotted with green, and densely scaly outside. There are ten stamens and a scaly ovary, and the fruit is a small dry capsule splitting to release numerous minute seeds.

Rhododendron triflorum belongs to subgenus Rhododendron (the lepidote, scaly-leaved rhododendrons), section Triflora, a group of slender-flowered species centred on the Sino-Himalaya. The lepidote indumentum and small capsular fruits with abundant wind-dispersed seed are characteristic of this clade. With a wide eastern Himalayan distribution the species is of least concern, and its handsome bark and yellow flowers have made it a valued ornamental; like its congeners it is an important component of the rhododendron-dominated temperate forests of the eastern Himalaya.

Author: Hook. f. · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Annotated Checklist of the Flowering Plants of Nepal, Cullen revision of lepidote Rhododendron

Ericaceae

Rhododendron tsariense

by GP Jürgens

Cowan

Bh2008 223 G352
Bhutan Tumching-La, 3800m April
Bh2008 224 P355
Bhutan Tumching-La, 3800m April
Bh09 339 G553
Bhutan Jakar 3700m April

Description

Rhododendron tsariense is a shrub of the eastern Himalaya, restricted to China (south-eastern Tibet), north-eastern India and Bhutan, with a small number of records (66 occurrences in GBIF) reflecting its limited range. It inhabits high subalpine and alpine zones, growing in open coniferous and Rhododendron scrub, on rocky slopes, ridges and the margins of fir forest, characteristically between about 3000 and 4300 m. The photographed plants come from Bhutan, at Tumching-La (3800 m) and near Jakar (3700 m), flowering in April as the high passes emerge from winter, an elevation typical of the species' montane habitat.

It is a compact, much-branched evergreen shrub, the young shoots and undersides of the leaves clothed in a dense, felted, fawn to rusty-brown indumentum that is one of its most diagnostic features. The leaves are small, leathery, elliptic to obovate, dark green and somewhat rugose above. The flowers are borne in small terminal trusses; the corolla is campanulate (bell-shaped), creamy white to pale pink, often flushed rose and spotted within. The fruit is a woody dehiscent capsule, the persistent style and calyx remaining at the apex.

The species belongs to subsection Lanata (subgenus Hymenanthes), a group of indumented eastern Himalayan rhododendrons characterised by their conspicuously hairy leaf undersurfaces. Named for the Tsari region, it is a narrow-range endemic of conservation interest, its alpine populations potentially sensitive to climate shifts and to grazing and burning pressure in the high pastures. Like other rhododendrons it is bee- and bird-pollinated and forms ericoid mycorrhizal associations adapted to acidic, peaty mountain soils.

Author: Cowan · Sources: POWO (Kew), GBIF, Flora of Bhutan, The Genus Rhododendron (Cowan & Davidian), Edinburgh Rhododendron revision

Ericaceae

Rhododendron vaccinioides

by GP Jürgens

Hook.

Bhutan2014 811
Bhutan Wangdi Mo-Chu 1600m, May
Nepal 97 108 P184
Nepal Dongen 2400m April
Nepal 1994 196 ergebnis
Ost-Nepal Mewa-Khola
2100m April

Description

Rhododendron vaccinioides is a small epiphytic rhododendron of the eastern Himalaya and adjacent China and Southeast Asia, recorded from China, India, Myanmar, Nepal, Bhutan, Vietnam and Japan, with some 245 GBIF occurrences. It grows as an epiphyte on mossy trunks and branches, and occasionally on rocks, in humid temperate broadleaved and conifer forest, generally between about 1600 and 3000 m. The documented populations span Wangdi Mo-Chu in Bhutan at 1600 m, Dongen in Nepal at 2400 m and the Mewa Khola in eastern Nepal at 2100 m, flowering in April and May in the cloud-bathed mid-montane belt.

It is a small, much-branched epiphytic shrub with slender, often pendent or sprawling branchlets bearing scattered scales (lepidote indumentum). The leaves are small, obovate to oblanceolate and somewhat fleshy, clustered toward the branch tips, vaccinium-like in aspect, hence the epithet, and lepidote beneath. The flowers are small, solitary or few at the branch ends, with a short-tubed, broadly funnelform to rotate, white to pinkish corolla that is sparsely scaly outside. The fruit is a small lepidote capsule splitting into valves to release numerous minute seeds adapted to wind dispersal among the canopy.

The species belongs to Rhododendron subgenus Rhododendron, section Vireya (the largely epiphytic, tropical-montane rhododendrons), of which it is one of the few representatives reaching the Himalaya. It is widespread and not threatened, but as an epiphyte dependent on humid, moss-laden old-growth forest it is sensitive to deforestation and to drying of the montane cloud belt.

Author: Hook. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, Argent monograph of Rhododendrons of Subgenus Vireya

Ericaceae

Rhododendron vaccinioides

by GP Jürgens

Hook. f.

Bhutan2014 43
Bhutan Trashigang 1300m, May
Bhutan2014 391
Bhutan Tumching-La 3000m, May
Bh2008 146 P243
Bhutan Chendebji, 2450m April

Description

Rhododendron vaccinioides Hook. f. is a small epiphytic rhododendron of the eastern Himalaya and adjacent montane Asia, ranging from Nepal and India through Bhutan to southern China, Myanmar and Vietnam, with around 245 GBIF occurrences. It grows characteristically as an epiphyte on mossy trunks and branches, and occasionally on rocks, in humid broadleaved and mixed evergreen forest, across a wide altitudinal span. The three Bhutan gatherings cited, from Trashigang at 1300 m and Chendebji at 2450 m flowering in April and May, and Tumching-La at 3000 m, illustrate its broad range from warm subtropical to cool temperate cloud forest where atmospheric moisture is high.

The species is a dwarf, much-branched epiphytic shrub with slender twigs clothed in scales and bearing small, obovate, leathery leaves whose lower surface is densely lepidote, resembling the foliage of Vaccinium as the epithet implies. The flowers are small, solitary or few together at the branch tips, with a short tubular to campanulate, white to pale pink corolla, the lobes spreading; the ovary and style are scaly. The fruit is a small lepidote capsule splitting septicidally to release numerous minute seeds adapted to wind dispersal in the canopy.

Rhododendron vaccinioides belongs to subgenus Rhododendron, section Vireya-allied scaly rhododendrons, an epiphytic lineage radiating through the wet forests of Asia. Its diminutive epiphytic habit is unusual among Himalayan rhododendrons. Widespread and locally frequent, it is of least conservation concern, though dependent on intact humid forest canopy.

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

Ericaceae

Rhododendron wallichii

by GP Jürgens

Hook. f.

Bhutan2014 988
Bhutan Chele-La 3900m, May
Bhutan2014 989
Bhutan Chele-La 3900m, May

Bh2008 575 P864 1
Bhutan Shele-La 3800m, May
Bh2008 573 P861 1
Bhutan Shele-La 3800m, May

Description

An evergreen rhododendron of the eastern Himalaya, native to China, Bhutan, Nepal and India, with about 353 GBIF occurrences (extra-range entries reflect cultivation in botanic gardens). It is a shrub to small tree of the upper subalpine and lower alpine zone, forming part of rhododendron-fir and dwarf rhododendron scrub, on cool, moist, humus-rich slopes generally between about 3300 and 4300 m. The depicted plants were photographed in May on the Bhutanese passes of Chele-La at around 3900 m and Shele-La at about 3800 m, exposed high-elevation habitats where it flowers as the snow recedes.

The species forms a rounded shrub with smooth, peeling bark and stout branchlets. The leaves are coriaceous, elliptic to oblong-elliptic, dark green and glabrous above, and beneath bear a distinctive thin, patchy, fawn to brownish indumentum of dendroid hairs that often wears away to leave scattered remnants. The flowers are borne in compact terminal trusses; each has a campanulate corolla of pale lilac to rose-pink, often with crimson basal blotches and spotting, the limb shallowly seven- to eight-lobed, with numerous stamens and a glabrous ovary topped by a slender style. The fruit is a curved, woody, septicidal capsule releasing many small winged seeds.

Though GBIF flags the name as a synonym, R. wallichii is widely accepted at species rank and placed in subsection Campanulata, allied to R. campanulatum, from which it is separated by its thinner, more fugacious leaf indumentum. Ecologically it is a major component of high Himalayan rhododendron heath, providing spring nectar and structural cover. Locally abundant within its range, it faces no immediate threat but is sensitive to grazing pressure, fire and the warming of its narrow alpine belt.

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