Author

GP Jürgens

Lamiaceae

Pogostemon linearis

by GP Jürgens

Kuntze

Bhutan2012 1165
Bhutan Trashiyangtse 1780m, October

Description

Pogostemon linearis is an Asian mint distributed through India, China, Bhutan, Myanmar, Bangladesh and westward to Iran, with around 99 georeferenced records in GBIF. It is a plant of warm-temperate to subtropical hill country, occurring on open grassy slopes, forest edges, streambanks and disturbed ground in the lower and middle montane zone. The Bhutanese material photographed near Trashiyangtse at about 1780 m in October reflects its typical autumn flowering at modest elevation, where it benefits from the warm, moist conditions of the eastern Himalayan foothills and frequently colonises seasonally damp, sunny situations.

The species is an erect to ascending herb or subshrub with quadrangular stems that are often pubescent. The leaves, as the epithet indicates, are narrow, linear to linear-lanceolate, sessile or shortly petiolate, with serrate to subentire margins and an acute apex. The flowers are borne in dense, cylindrical, spike-like verticillasters forming a terminal thyrse; each small flower has a tubular, five-toothed calyx and a campanulate, weakly two-lipped corolla. The four stamens are characteristically long-exserted and bear conspicuously bearded filaments, a diagnostic feature of Pogostemon, giving the inflorescence a fluffy appearance. The fruit comprises four smooth nutlets enclosed by the persistent calyx.

Described by Kuntze, P. linearis belongs to a genus best known for P. cablin, the source of patchouli oil. The bearded, far-exserted stamens place it firmly within Pogostemon and distinguish it from related Lamiaceae genera. Its broad distribution, ecological tolerance and association with open and disturbed habitats indicate a secure conservation status throughout its range.

Author: Kuntze · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, Bhatti & Ingrouille revision of Pogostemon

Polygalaceae

Polygala arillata

by GP Jürgens

Buch.-Ham. ex D. Don

Bhutan2014 669
Bhutan Wangdi-Phodrang 2280, May

Description

Polygala arillata is a shrubby milkwort of the Himalaya and Southeast Asia, distributed from Nepal, NE India and Bhutan through southern China to Myanmar, Thailand, Vietnam, Bangladesh, Sri Lanka and Malesia, with 2,908 GBIF occurrences. It grows in temperate and subtropical broad-leaved forest, forest margins, clearings and shrubby slopes, commonly between about 1,000 and 2,800 m. The Bhutanese collection from Wangdi Phodrang at about 2,280 m in May reflects its late-spring flowering in mid-montane forest, where it grows as a conspicuous understorey or edge shrub.

It is an erect shrub or small tree 1–3 m tall with terete, finely pubescent branchlets. The leaves are alternate, elliptic to obovate-oblong, 8–18 cm long, acuminate, entire and shortly petiolate, often somewhat membranous. The inflorescence is a pendent terminal or leaf-opposed raceme of showy flowers; each flower has five sepals, the two inner enlarged into petaloid, deep yellow to reddish wings, and three petals fused into a tube with a fringed keel, the whole strongly zygomorphic. The fruit is a fleshy, laterally compressed, reddish capsule, and the seeds bear a conspicuous white aril, from which the epithet arillata is derived.

The species belongs to the large, cosmopolitan genus Polygala and is among its more robust, woody Asian representatives. GBIF treats the name as accepted. The arillate seeds suggest dispersal by birds or ants attracted to the fleshy appendage, and the showy keeled flowers are adapted to insect pollination. Widespread and locally common, it is of least concern; its roots and bark are used in regional traditional medicine.

Author: Buch.-Ham. ex D. Don · Sources: POWO (Kew), Flora of China Vol. 11, Flora of Bhutan Vol. 1, GBIF, Bennett: Polygalaceae in Hooker's Flora of British India (1882)

Polygalaceae

Polygala sibirica

by GP Jürgens

L.

Bh2008 521 G796
Bhutan Punakha 2400m, May

Description

Polygala sibirica L. is a small perennial milkwort with one of the widest distributions in its genus, ranging across temperate Eurasia from eastern Europe through Central and northern Asia to the Himalaya, China, Japan and southward into Southeast Asia and Australasia. GBIF records confirm its presence in Russia, China, Mongolia, India, Nepal, Bhutan, Pakistan, Korea, Japan and many other countries, with several thousand occurrences. It grows on dry grassy slopes, open stony banks and forest margins from the lowlands to about 3,000 m. The plant photographed at Punakha in Bhutan at 2,400 m, flowering in May, exemplifies its occurrence on sunny montane slopes.

The species is a tufted perennial herb arising from a woody rootstock, with several ascending to spreading, often hairy stems 10–30 cm long. The leaves are alternate, sessile or nearly so, lanceolate to elliptic, the lower ones smaller. The flowers are borne in lax terminal racemes; the two large petaloid lateral sepals (wings) are greenish-veined, and the small blue to purplish corolla bears a conspicuous fringed keel-petal crest. The fruit is a flattened, narrowly winged, obcordate capsule containing two hairy seeds with a small aril.

Polygala sibirica is closely allied to the medicinally important P. tenuifolia, and its roots are similarly used in traditional Chinese medicine (yuan zhi) as a source of saponins. Its enormous range and ecological tolerance make it one of the most successful milkworts, and it is of least conservation concern.

Author: L. · Sources: POWO (Kew), GBIF, Flora of China Vol. 11, Flora of Bhutan Vol. 1, Bennett: Polygalaceae in Hooker's Flora of British India

Asparagaceae

Polygonatum cirrhifolium

by GP Jürgens

(Wall.) Royle

Bh2008 611 P920
Bhutan, Punakha 2400m, May

Description

Polygonatum cirrhifolium is a rhizomatous perennial herb widely distributed across the Himalaya and the mountains of central and western China, recorded from China, Nepal, India, Bhutan, Myanmar and Vietnam, with around 2251 georeferenced records (records from Canada, Norway and Britain reflect cultivation). It occurs in temperate forest, forest margins, shrubberies and grassy alpine slopes, on moist humus-rich soils typically between about 2000 and 4000 m. The photographed plant from Punakha in Bhutan at 2400 m, flowering in May, sits near the lower edge of its broad altitudinal span.

It has a stout, knotted, horizontal rhizome from which arises an erect to arching stem. The narrow, linear-lanceolate leaves are borne in whorls of three or more, and the epithet cirrhifolium refers to their slender apices, which are characteristically prolonged and curled into tendril-like tips. The pendent flowers hang one to four together in the leaf axils; each perianth is tubular, pale rose-purple to whitish, the six tepals fused into a cylinder with short lobes and enclosing six stamens. The fruit is a globose berry that ripens from red to purplish-black.

Polygonatum, in Asparagaceae subfamily Nolinoideae, is here represented by a whorled-leaved species readily told from P. oppositifolium by its tendrilled leaf tips. The rhizome, known in Chinese and Himalayan medicine, is gathered as a tonic drug, and the species is among the sources of the herbal material huangjing. The pendent nectar-bearing flowers are bumblebee-pollinated and the berries bird-dispersed. Though widespread and not threatened overall, sustained medicinal harvesting locally depletes wild populations.

Author: (Wall.) Royle · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Annotated Checklist of the Flowering Plants of Nepal, Jeffrey monograph of Polygonatum

Asparagaceae

Polygonatum hookeri

by GP Jürgens

Baker

Sikkim2011 51
Sikkim Vista-valley 3800m, June
Bhutan2014 991
Bhutan Chele-La 4000m, May

Description

Polygonatum hookeri is a dwarf alpine Solomon's-seal of the Sino-Himalayan high mountains, recorded from China, Nepal, India, Bhutan and Pakistan across some 400 GBIF occurrences. The illustrated plants were photographed in the Vista-valley of Sikkim at 3800 m in June and on the Chele-La in Bhutan at 4000 m in May. It grows in open alpine turf, on grassy slopes, stony meadows and the margins of rhododendron scrub, typically between 3000 and 4500 m, forming low patches in short high-elevation vegetation where it flowers soon after snowmelt.

The plant is a diminutive rhizomatous perennial, spreading by a slender creeping rhizome and producing very short, sometimes almost stemless aerial shoots. The leaves are small, narrowly elliptic to oblong and crowded toward the top of the shoot. The flowers are solitary or paired and conspicuously large relative to the plant, bell- to funnel-shaped, lilac, rose-pink or purplish, borne low among the leaves; the perianth is tubular with six short lobes. The fruit is a small globose berry, ripening red, containing few seeds.

Long placed in the Liliaceae or Convallariaceae, Polygonatum is now treated in the Asparagaceae (subfamily Nolinoideae). P. hookeri is among the smallest and most alpine members of the genus, its dwarf cushion-like habit an adaptation to the harsh high-mountain environment, and it is much esteemed by rock-garden growers. The bird-dispersed berries aid colonisation of new ground. The species is widespread across the high Himalaya and of least conservation concern.

Author: Baker · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Flora of Nepal, Jeffrey – The Genus Polygonatum (Liliaceae/Asparagaceae) revision

Asparagaceae

Polygonatum oppositifolium

by GP Jürgens

(Wall.) Royle

Nepal 97 328 P653
Nepal Arun-Valley 2000m May

Description

Polygonatum oppositifolium is a rhizomatous perennial herb of the Himalaya and adjacent mountains, ranging through India, Nepal, China, Bhutan and Myanmar, with around 184 georeferenced records concentrated along the southern Himalayan flank (several distant country codes reflect cultivation or data artefacts rather than wild populations). It grows in moist, shaded broad-leaved and mixed forest, on banks and among rocks in leaf-litter-rich soils at middle elevations. The photographed plant from the Arun Valley of eastern Nepal at about 2000 m, flowering in May, typifies its warm-temperate forest habitat.

The plant has a creeping, knotted, fleshy rhizome from which arises an arching to suberect stem. As the epithet indicates, the lanceolate to ovate-lanceolate leaves are predominantly opposite (occasionally whorled), sessile to shortly petiolate, acuminate and prominently veined. The flowers hang in short axillary cymes; each perianth is tubular and greenish-white, the six tepals fused into a cylindrical tube with short recurved lobes, enclosing six included stamens with filaments adnate to the tube. The fruit is a small globose berry, ripening dark blue to blackish and containing few seeds.

Polygonatum (Solomon's seal), placed in Asparagaceae subfamily Nolinoideae, is distinguished from related genera by its rhizome scars and tubular flowers. P. oppositifolium is notable within the Himalayan members for its opposite leaf arrangement. The pendent flowers are bumblebee-pollinated and the berries bird-dispersed. The rhizomes are gathered locally in traditional medicine; while not currently regarded as threatened, such harvesting and forest degradation warrant monitoring of wild stands.

Author: (Wall.) Royle · Sources: POWO (Kew), GBIF, Flora of China, Annotated Checklist of the Flowering Plants of Nepal, Flora of Bhutan, Jeffrey monograph of Polygonatum

Asparagaceae

Polygonatum punctatum

by GP Jürgens

Royle ex Kunth

Bh2008 333 P513
Bhutan Phobjika 2700m, April
Nepal 1994 59 ergebnis
Ost-Nepal Bhalukhob 
1900m April

Description

Polygonatum punctatum is a Sino-Himalayan Solomon's seal distributed through China, Nepal, India, Bhutan, Myanmar, Thailand, Vietnam and Laos, with over 450 georeferenced occurrences and additional records from cultivation. It is a plant of cool, shaded temperate forest, mossy banks, rock ledges and humus-rich slopes, where it often grows as a lithophyte or epiphyte. The populations documented at Phobjikha in Bhutan at about 2700 m and at Bhalukhob in eastern Nepal at about 1900 m, both in April, reflect its montane forest habitat, emerging and flowering in spring.

The species grows from a creeping, knotted rhizome that produces an arching to pendent leafy stem. The leaves are alternate, sometimes appearing sub-opposite, ovate to lanceolate and acuminate, often somewhat leathery. Slender axillary inflorescences bear one to several tubular flowers; the perianth is fused into a narrow cylindrical tube, greenish-white and frequently marked with purple dots or spots (the punctate patterning evoked by the epithet), with six short lobes and included stamens. The fruit is a small globose berry, dark purple to blackish when ripe, containing a few seeds.

Within Asparagaceae (formerly Convallariaceae or Liliaceae sensu lato), Polygonatum is a Northern Hemisphere genus whose East Asian and Himalayan species are taxonomically intricate, separated by leaf arrangement, flower number, perianth markings and rhizome form. The frequently epiphytic or saxicolous habit of P. punctatum is unusual within the largely terrestrial genus. Widespread and locally common, it is not regarded as threatened, though several Himalayan congeners are harvested for the medicinal rhizome.

Author: Royle ex Kunth · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of Nepal, Flora of China, Jeffrey's revision of Polygonatum

Polygonaceae

Polygonum filicaule

by GP Jürgens

Wall. ex Meisn.

Bh09 277 P456
Bhutan Phobjika 2800m, June

Description

Polygonum filicaule is a small Himalayan and East Asian knotweed ranging from the Himalaya through southern China to Taiwan and Japan; GBIF lists around 358 occurrences across China, India, Pakistan, Japan and Taiwan. It inhabits cool, moist temperate sites, growing in damp turf, moss carpets, stream banks, marshy meadows and seepage zones, often as a prostrate component of open subalpine grassland. The accompanying photograph from Phobjika in Bhutan at about 2800 m in early June shows the species at the start of its flowering season in the broad, marshy glacial valley floors for which that locality is well known. Under POWO this name is treated as a synonym, the accepted name being Persicaria filicaulis.

It is a delicate, creeping, mat-forming perennial herb with thread-like (filiform), much-branched stems that root at the lower nodes, the epithet filicaule alluding to these slender stems. The ochreae are membranous, tubular and shortly ciliate, sheathing the nodes. Leaves are small, ovate to oblong-lanceolate, shortly petiolate or subsessile, with entire margins and often a fine pubescence. Flowers are minute and few, borne in short, lax terminal or axillary clusters; the perianth is five-parted, white to pink, persistent and enclosing the fruit. The achene is small, trigonous, dark brown and lustrous.

The species belongs to a group of diminutive, mat-forming Asian polygonums now widely placed in Persicaria, distinguished from robust upright knotweeds by their creeping habit and reduced inflorescences. As a wetland and seepage specialist it contributes to high-altitude turf communities and is well adapted to grazed, trampled and seasonally waterlogged ground. It is not considered threatened, being widespread and tolerant of disturbance, though dependent on the persistence of moist montane grassland.

Author: Wall. ex Meisn. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China (Polygonaceae), Hara & Williams Enumeration of the Flowering Plants of Nepal

Pontederiaceae

Pontederia hastata

by GP Jürgens

L.

Nepal 97 548 P1074
Nepal Sabha-Khola 530m May

Description

Pontederia hastata is an aquatic to semi-aquatic herb of tropical and subtropical Asia and Australasia, with 931 GBIF occurrences extending from India, Nepal, China and Sri Lanka through Southeast Asia to the Philippines, Papua New Guinea, Fiji and northern Australia. It grows in still and slow-moving fresh water, inhabiting ponds, ditches, marshes, paddy fields and the margins of streams and pools in the lowlands and low hills. The plant recorded along the Sabha-Khola in Nepal at 530 m in May exemplifies its lowland wetland habitat, where it grows rooted in shallow water or mud and flowers in the warm pre-monsoon period.

The species is a perennial, more or less emergent herb arising from a creeping rhizome and rooting at the nodes. The leaves are long-petiolate, the petioles sometimes slightly spongy and inflated, bearing sagittate to hastate blades with diverging basal lobes that give the plant its epithet. The flowers are borne in a dense spike or raceme subtended by a leaf-like spathe; each is bluish to pale violet, with six perianth segments fused below into a tube, six stamens often differing in length, and a tricarpellate ovary. The fruit is a capsule enclosing numerous small seeds dispersed by water.

The taxon has long been known as Monochoria hastata, reflected in the source link, but Monochoria is now subsumed within an enlarged Pontederia on phylogenetic grounds, making Pontederia hastata the accepted name. Like its relatives, the plant is an effective coloniser of disturbed aquatic and agricultural wetlands; it is widely used as a leaf vegetable and remains common, of no conservation concern across its broad range.

Author: L. · Sources: POWO (Kew), GBIF, Flora of China Vol. 24, Flora of Bhutan Vol. 3, Flora of Nepal, Flora of Pakistan, Pellegrini's revision of Pontederiaceae

Salicaceae

Populus tremula

by GP Jürgens

L.

Bhutan2014 957
Bhutan Chele-La 3400m, May
Bhutan2014 958
Bhutan Chele-La 3400m, May

Description

Populus tremula, the Eurasian aspen, is among the most widely distributed trees of the Northern Hemisphere, ranging across virtually all of Europe and temperate Asia, as the vast GBIF dataset of over 779,000 records from Sweden, France, Germany, Britain, Russia, China and beyond attests. In the Himalaya it reaches its southern Asian limit as a high-montane element, and the photographed tree from Bhutan's Chele-La at 3400 m in May represents this elevated outpost. It is a pioneer of disturbed ground, forest clearings, burnt areas, screes and woodland margins, tolerant of a wide range of soils and climates from boreal lowland to subalpine slopes, where it often forms clonal stands by root suckering.

It is a deciduous tree with smooth, greenish-grey bark, becoming furrowed at the base of old trunks. The alternate leaves are nearly orbicular to broadly ovate with a crenate to sinuate margin, borne on long, conspicuously laterally flattened petioles that allow the foliage to flutter in the slightest breeze, the trait giving the tree both its epithet tremula ("trembling") and its English name. Juvenile and sucker leaves are larger and more triangular. Like all poplars it is dioecious, the flowers borne in pendulous catkins that appear before the leaves; each flower subtended by a fringed bract, the males with numerous stamens, the females with a one-celled ovary. The fruit is a small capsule releasing cottony, plumed seeds dispersed by wind.

Aspen is a keystone pioneer species of immense ecological importance, supporting rich communities of insects, fungi and lichens and frequently forming genetically uniform clonal groves that can persist for centuries. Within Salicaceae it belongs to section Populus (the aspens and white poplars). Its presence in the eastern Himalaya illustrates the trans-Eurasian continuity of temperate forest floras; the species is of least conservation concern and is widely exploited for timber, pulp and matchwood.

Author: L. · Sources: POWO (Kew), GBIF, Flora of China Vol. 4, Flora of Bhutan Vol. 1, Flora of Pakistan, Eckenwalder's Conifers and Salicaceae Treatments