New records of flowering plants for the Flora of Bhutan

Phub GYELTSHEN; Kezang TOBGAY; Phuentsho PHUENTSHO; Karma SANGAY; Karma D. DORJI; David LONG; Sangay DEMA

doi:10.11110/kjpt.2025.55.2.88

Korean J. Pl. Taxon > Volume 55(2); 2025 > Article

GYELTSHEN, TOBGAY, PHUENTSHO, SANGAY, DORJI, LONG, and DEMA: New records of flowering plants for the Flora of Bhutan

Research Article

Korean Journal of Plant Taxonomy 2025; 55(2): 88-102.

Published online: June 30, 2025

DOI: https://doi.org/10.11110/kjpt.2025.55.2.88

New records of flowering plants for the Flora of Bhutan

Phub GYELTSHEN^*

, Kezang TOBGAY

, Phuentsho PHUENTSHO

, Karma SANGAY¹

, Karma D. DORJI

, David LONG²

, Sangay DEMA

National Biodiversity Centre, Ministry of Agriculture and Livestock, Thimphu, Bhutan

¹Bumdeling Wildlife Sanctuary, Department of Forests and Park Services, Lhuentse, Bhutan

²Royal Botanic Garden Edinburgh, Inverleith Row, Edinburgh EH3 5LR, UK

Corresponding author: Phub GYELTSHEN, E-mail: gyeltshenforest@gmail.com

Received February 17, 2025 Revised May 9, 2025 Accepted May 11, 2025

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The present study was designed to assess the diversity of native flora in Bhutan, focusing on the collection of specimens for long-term conservation and research. The following three exotic (Achimenes longiflora, Ipomoea triloba, and Lippia alba) and 16 native plant species were confirmed as new records in the Flora of Bhutan: Biophytum reinwardtii, Breynia macrantha, Bridelia assamica, Burmannia nepalensis, Ceropegia khasiana, Diospyros lanceifolia, Goniothalamus sesquipedalis, Gymnocladus assamicus, Grewia serrulata, Hypericum podocarpoides, Melastoma malabathricum, Ormosia robusta, Peliosanthes maheswariana, Phlogacanthus curviflorus, Sterculia lanceolata and Vincetoxicum belostemma. These findings will enhance our understanding of plant diversity in Bhutan and contribute to advancing botanical knowledge in the region. Brief descriptions, including information on the type, phenology, and distribution for each species, are provided to facilitate identification and conservation.

Keywords: Bhutan, distribution, Eastern Himalayas, endemic, exotic, native

INTRODUCTION

Bhutan, situated in South Asia, is part of the Himalayan biodiversity hotspot (Habel et al., 2019; Critical Ecosystem Partnership Fund, 2024). The Himalayan biodiversity hotspot comprises approximately 10,000 species of vascular plants, of which approximately 3,160 are endemic to the region (Critical Ecosystem Partnership Fund, 2024). Bhutan has very rich and diverse flora, comprising numerous economically important plants such as timber trees and medicinal herbs, and especially many attractive and desirable horticultural groups, particularly Orchidaceae, Primulaceae, and Ericaceae (Grierson and Long, 1983). More specifically, the multiple biogeographic origins, diverse topography, ecological complexity, and a wide range of climatic and soil conditions support a diverse range of floristic complexes (Grierson and Long, 1983; P. Gyeltshen et al., 2023a). Grierson and Long (1983) classified forest vegetation into eleven types based on the dominant plant characteristic, amount of rainfall, and altitude. These were subtropical forests, warm broadleaved forests, chir pine forests, cool broadleaved forests, evergreen oak forests, blue pine forests, spruce forests, hemlock forests, fir forests, juniper and rhododendron scrub, and dry alpine scrub. Of these, cool broadleaved forest represents 26% of the total forest cover (69.7%) in Bhutan (FMID, 2023).

Botanical exploration in Bhutan began in 1838 when William Griffith, the first botanist to enter Bhutan, collected around 1,200 plant specimens from several districts (Grierson and Long, 1983). However, his collections were included in the flora of British India. The mission was followed by that of the diplomat J. C. White in 1906 and 1907, who collected 250 specimens, mostly from western Bhutan. From 1914 onwards, several privileged plant explorers visited Bhutan (Grierson and Long, 1983). The most notable of these were Frank Ludlow and George Sherriff, who collected 6195 specimens between 1922 and 1950 (Grierson and Long, 1983). In the mid-1970s, Bhutan’s Flora project was initiated at the request of the Royal Government of Bhutan to the British Government to generate a complete checklist and list of synoptic flora of flowering plants. The Flora of Bhutan series, with three volumes each consisting of three parts, was published between 1983 and 2002. According to the Flora of Bhutan (Grierson and Long, 1983, 1984, 1987, 1991, 1999, 2001; Noltie, 1994, 2000), Orchids of Bhutan (Pearce and Cribb, 2002) and Pteridophytes of Bhutan (Fraser-Jenkins et al., 2023), there are 6448 taxa of vascular plants belonging to 267 families, 1749 genera, 271 subspecies and 495 varieties. The Flora series also includes species occurring in neighbouring regions of Darjeeling in West Bengal and Sikkim of India. Pteridophytes of Bhutan (Fraser-Jenkins et al., 2023) is not part of the Flora series and it is a recently published and new flora document for Bhutan. The fern and allies are highly diverse with 563 species and 66 subspecies in 93 genera (Fraser-Jenkins et al., 2023) followed by orchids with 498 species in 132 genera (Gyeltshen et al., 2024).

Subsequent to these publications, there has been a sharp increase in the number of recorded species of plants due to recent discoveries of species, both new to science and new records for Bhutan (Rushforth, 1991, 1992a, 2009; Yamazaki, 2003; Maity and Springate, 2004; Gangophadhyay, 2006; Gurung, 2006; Fryer and Hylmö, 2009; Kadota, 2010; Lidén, 2010; Ohba and Akiyama, 2010; Podlech, 2010; Sukhorukov, 2012; Yoshida and Grey-Wilson, 2012; Ranjan et al., 2013; Long, 2014; Yoshida et al., 2014, 2016, 2017a; Dalström et al., 2017; Gurung et al. 2020; N. Gyeltshen et al., 2017, 2020; C. Gyeltshen et al., 2019: P. Gyeltshen et al., 2019, 2020, 2021a, 2021b, 2021c, 2021d, 2021e, 2022, 2023a, 2023b, 2023c, 2023d, 2024; Rabgay and Kumar, 2019; Tobgay et al., 2019; Chaida and Tashi 2020; Dechen et al., 2020; Gyeltshen and Dema, 2020; S. Wangchuk et al., 2020, 2024; Gyeltshen and Jamtsho, 2021; Pendry, 2021; Rabgay et al., 2021; Tshewang et al., 2021; Zangpo et al., 2021; Dorji et al., 2022; Ghalley et al., 2022; Dorjee et al., 2023; Dorji et al., 2023; Fraser-Jenkins et al., 2023; Jamtsho et al., 2023; J. Wangchuk et al., 2023; Wangdi, 2023; Thukten et al., 2024; Tobgay et al., 2024b, 2024b; Tshering et al., 2024a, 2024b; T. Wangchuk et al., 2024). Based on extensive research and a review of all available literature and publications on new taxa and new records, there are 5398 species validly documented in Bhutan, including 282 bryophytes. Of these, 153 species are endemic to Bhutan. Unlike some neighbouring countries with intensive botanical investigations and a modern taxonomic treatment of floral biodiversity, the Flora of Bhutan lacks a fully up-to-date taxonomic treatment. There are many species complexes that need revision due to recent advances in plant taxonomy and systematics.

MATERIALS AND METHODS

The present study was based on intensive field surveys and collections made by Phub Gyeltshen, Kezang Tobgay, and Phuentsho Phuentsho between April of 2023 and November of 2024 during different seasons and at various localities of the country (Fig. 1). A few specimens of the newly recorded taxa collected in the past, which had remained undocumented, are also treated in this study. In total, approximately 1,000 herbarium specimens of plants were collected. The specimen collection and processing techniques follow Davies et al. (2023). Samples were air-dried or dried with the help of a fan heater, and the dried specimens were deposited at the herbarium THIM, National Biodiversity Centre, Thimphu, Bhutan. All collected specimens were identified by means of a literature review (Austin, 1978; Skog, 1978; Grierson and Long, 1987, 1991, 1999, 2001; Noltie, 1994; Meyer, 2001; Lu and Spongberg, 2003; Ya et al., 2007; Peng et al., 2008; Wu et al., 2010; Sinha et al., 2014; Venugopal and Pamidimarri, 2015; Murugesan et al., 2019; Borah et al., 2024) and by examining virtual herbarium specimens of the herbaria ASSAM, BM, CAL, E, G, K, KATH, L, M, PE, and SING as well as physical specimens at the THIM herbarium (Thiers et al., 2024, continuously updated). Furthermore, various online resources, such as JSTOR Global Plant (https://plants.jstor.org), the Global Biodiversity Information Facility (https://www.gbif.org/), iNaturalist (2024) (https://www.inaturalist.org) and the Bhutan Biodiversity Portal (https://biodiversity.bt/) were used to confirm the species identity and to locate other information. For binomial nomenclature and authorities, the International Plant Names Index (International Plant Names Index, 2024, continuously updated) was followed, and Plants of the World Online (Plants of the World Online, 2024, continuously updated) was consulted to check the distribution of the species.

For morphological characterizations, color notations, structures, and descriptions, we follow Beentje (2024) and the Flora of Bhutan. Measurements of the vegetative and reproductive parts were taken in-situ and from freshly collected materials. Geographical details such as elevations and geo-coordinates were collected using a Garmin GPS device (Etrex 30x) and were photographed in the field using a digital camera. Distributional data were plotted on a map (Fig. 1) using QGIS software version 3.38.1 (QGIS Development Team, 2024). The Flora of Bhutan is used as the basis to report new records for Bhutan. The new records reported here are arranged in alphabetical order of the family names, along with their voucher information. Locations of the newly reported species are indicated by numerals, which also correspond to the species number in this paper. Brief descriptions, with information on distribution and available types, are provided for each species. In the citations of the specimens examined, distributional data follow the administrative boundaries currently used in Bhutan.

RESULTS AND DISCUSSION

Nineteen species of flowering plants belonging to 19 genera in 15 families are reported as new records for the Flora of Bhutan. Of these, 16 species—Biophytum reinwardtii (Zucc.) Klotzsch (Oxalidaceae), Breynia macrantha (Hassk.) Chakrab. & N. P. Balakr. and Bridelia assamica Hook. f. (Phyllanthaceae), Burmannia nepalensis (Miers) Hook. f. (Burmanniaceae), Ceropegia khasiana Murug., A. A. Mao, Meitei & Kambale (Apocynaceae), Diospyros lanceifolia Roxb. (Ebenaceae), Goniothalamus sesquipedalis (Colebr.) Hook. f. & Thomson (Annonaceae), Grewia serrulata DC. (Malvaceae), Gymnocladus assamicus Kanjilal ex P. C. Kanjilal (Fabaceae), Hypericum podocarpoides N. Robson (Hypericaceae), Melastoma malabathricum L. (Melastomataceae), Ormosia robusta (Wight) Voigt (Fabaceae), Peliosanthes maheswariana D. Borah, N. Tanaka & Taram (Asparagaceae), Phlogacanthus curviflorus (Nees) Nees (Acanthaceae), Sterculia lanceolata Cav. (Malvaceae), and Vincetoxicum belostemma (Benth.) Kuntze (Apocynaceae) are native to South and Southeast Asia. The notable discoveries include Gymnocladus assamicus and the recently described Ceropegia khasiana and Peliosanthes maheswariana, which thus far were considered endemic to India. The other three species—Achimenes longiflora DC. (Gesneriaceae), Ipomoea triloba L. (Convolvulaceae) and Lippia alba (Mill.) N. E. Br. ex Britton & P. Wilson (Verbenaceae) are native to Central and South America but have been introduced to other tropical and subtropical regions of the world.

The genus Achimenes and the species Hypericum podocarpoides, Ormosia robusta, and Burmannia nepalensis are new to the Flora of Bhutan. Biophytum reinwardtii, Breynia macrantha, Bridelia assamica, Diospyros lanceifolia, Goniothalamus sesquipedalis, Grewia serrulata, Melastoma malabathricum, Phlogacanthus curviflorus, Sterculia lanceolata and Vincetoxicum belostemma are treated in the Flora of Bhutan based on their occurrence in the Darjeeling and Sikkim regions of India. In this study, we have validly documented these species based on specimens and data, and they are now confirmed as new records for Bhutan.

New records

Acanthaceae Juss.

1. Phlogacanthus curviflorus (Wall.) Nees, in Wallich, Pl. Asiat. Rar. 3: 99, 1832; Justicia curviflora Wall., Pl. Asiat. Rar. 2: 9, 1831.—TYPE: India. Meghalaya, Mont Sillet, Oct 1828, Wall. Cat. 2429A (lectotype: K, 001115916, designated by Deng, 2020, Photo!) (Fig. 2A).

Shrubs, 2–4 m tall, hairy. Petiole 2–9 cm long, pubescent; lamina broadly ovate to elliptic, 15–30.5 × 6–19.5 cm, base cuneate, margin entire to subcrenate, apex acute to acuminate, abaxially pubescent along veins, adaxially glabrous, secondary veins 7–10 on each side of midvein. Inflorescence terminal, 8–20 cm long; flowers numerous, pubescent; pedicel 3–7 mm long, densely tomentose; bracts oblanceolate or lanceolate, 3–7 × 1–2 mm; bracteoles subulate, 2–3.5 mm long; calyx tube ca. 1 mm long; lobes lanceolate, ca. 3–4 × 1 mm, sparsely pubescent abaxially, densely brown pubescent abaxially; corolla deep reddish purple, densely brownish pubescent abaxially; tube ca. 2.5 cm long; lower lip 3-lobed, lobes oblong and ca. 2 × 1.5 mm; upper lip 2-cleft; stamens 2, slightly exserted; filaments ca. 2 cm long, glabrous; anther thecae ellipsoid, ca. 3 × 2 mm long, not exserted; staminodes 2, small. Ovary oblong, 4–6 mm long, style 2–2.4 cm long, glabrous.

Flowering: October–May.

Distribution: Phlogacanthus curviflorus is native to China, India, Laos, Myanmar, Thailand, Vietnam, and Bhutan (Pemagatshel district; reported here).

Specimens examined: BHUTAN. Pemagatshel district: Nganglam, elev. 374 m, 26.8141°N, 91.2583°E, 4 Dec 2023, P. Gyeltshen, K. Tobgay, C. Wangmo & Sampa 197 (THIM22734, THIM22735 & THIM22736).

Annonaceae Juss.

2. Goniothalamus sesquipedalis (Colebr.) Hook.f. & Thomson, Fl. Ind. [Hooker f. & Thomson] i. 108, 1855; Guatteria sesquipedalis Colebr., in Wall., Pl. Asiat. Rar. 3: 42, t. 266, 1832.—TYPE: INDIA. Meghalaya, Sillet, W.G[omez], Wall. Cat. 6446 (holotype: K, 001123935, Photo!) (Fig. 2B).

Shrub or undershrub about 3–4 m tall. Branches glabrous and sparingly branched. Leaves simple, alternate, coriaceous; petiole subsessile; lamina oblanceolate-elliptic to oblong-elliptic, 20–40 × 4–11 cm, acuminate, base cuneate, margin entire, revolute, apex acute or shallow acuminate, lateral veins 15–20 pairs. Flowers solitary or in pairs, axillary or supra-axillary, greenish-yellow; pedicels stout, up to 5 mm long, bracteate at base; sepals ovate, 6–7 × 4–5 mm. Petals 6 in 2 series, subequal; outer petals ovate-lanceolate, 15–20 × 3–5 mm, apex acute or acuminate; inner petals 11–13 × 4–5 mm, shortly clawed and free in lower part. Fruit ovoid, 2–2.5 × 1 cm, acute, orange red when mature; stamens numerous, linear oblong, 1.3–1.5 mm long; carpels oblong, hairy, 3–4 mm long, style slightly curved.

Flowering: May–December.

Distribution: Goniothalamus sesquipedalis is distributed in China (South–Central), India, Myanmar and Bhutan (Dagana district; reported here).

Specimens examined: BHUTAN. Dagana district: Lhamoizingkha, Samar, elev. 400 m, 26.8174°N, 89.9142°E, 27 Nov 2023, P. Gyeltshen, K. Tobgay, C. Wangmo & Sampa 139 (THIM22582 & THIM22581).

Apocynaceae Juss.

3. Ceropegia khasiana Murug., A. A. Mao, Meitei & Kambale, Gard. Bull. Singapore 71: 520, 2019.—TYPE: India. Meghalaya, Ri-Bhoi District, East Khasi Hills, 950 m above sea level, 10 Jul 2017, Murugesan 137313 (holotype: ASSAM-not seen) (Fig. 2C).

Perennial, twining herb up to 3.5 m long. Stem slender, terete, sparsely pubescent or glabrous. Roots fascicled, fusiform, fleshy, short, up to 7.5 cm long. Leaves simple, opposite; petiole up to 1.6 cm long, with sparse row of hairs; lamina lanceolate, 5.5–14 × 0.7–3 cm, base attenuate, apex acuminate, margin entire, adaxially sparse pubescent, abaxially sparsely pubescent on nerves. Inflorescences axillary, umbellate cymes, single or 2–15-flowered, peduncles 1–2.8 cm long, sparsely pubescent hairy; pedicels 1–1.6 cm long; bracts 1 or 2, lanceolate, 1.3–1.8 mm long, apex acute, margin ciliated; calyx lobes lanceolate, 5–6.5 × 0.5–0.8 mm, apex acuminate; corolla 4–4.5 cm long, sparsely minutely hairy outside at base, dense towards apex, glabrous within; corolla tube 2–2.5 cm long, purplish red streaked and blotches outside, deep purple red inside, inflated base; lobes lanceolate, 12–15 × 4.5–5 mm, folded, keeled, ciliate hairy within, pinkish white. Corona biseriate; outer with five bifid lobes, 1–1.2 mm long, lobes sparsely ciliate; inner lobes linear-lanceolate, 2–2.5 mm long, orange-red at base, yellowish white towards apex, glabrous. Pollinia ovoid, 0.3–0.4 × 0.2–0.3 mm, yellow; caudicles short, c. 0.3 mm long; corpusculum clavate, ca. 0.25 mm long. Ovary conical, c.1.8–2 × 0.5 mm, glabrous.

Flowering: July–October.

Distribution: Ceropegia khasiana was formerly considered endemic to Meghalaya, India.

Specimen examined: BHUTAN. Zhemgang district: Trong block, Dakphel, elev. 1400 m, 27.1964°N, 90.7114°E, 2 Sep 2022, T. Tobgay, N. Gyeltshen & Sampa 531 (THIM23526).

4. Vincetoxicum belostemma (Benth.) Kuntze, Revis. Gen. Pl. 2: 424, 1891; Tylophora belostemma Benth. in Benth. & Hook. f., Gen. Pl. 2: 771, 1876, Belostemma hirsutum Wall. ex Wight, Contr. Bot. Ind. 52, 1834.—TYPE: Nepal. Wallich, s.n. (holotype: K, 000872929, Photo!) (Fig. 2D).

Slender climbing shrub, with long twining branches, densely hirsute throughout. Leaves opposite; petiole 3–10 mm long; lamina ovate to lanceolate, 1.5–5 × 0.7–2.5 cm, apex acuminate, base cordate to rounded, membranous. Inflorescence shortly umbel; flowers purple, small, 7–8 mm across, few-flowered; peduncle short, 2–5 mm long; pedicels 3–5 mm long; calyx lobes narrowly lanceolate, 2–2.6 × 0.5–0.6 mm; corolla glabrous outside, pubescent within; tube ca. 1 mm long; lobes ovate, 2.6–3 × 1.3–1.6 mm; gynostegium ca. 1.5 mm high, ca. 1 mm across stigmatic head; staminal corona scales linear, ca. 1 mm long, horizontally spreading. Follicles unknown.

Flowering: June–July.

Distribution: Vincetoxicum belostemma is native to Bhutan, China, India and Nepal.

Specimens examined: BHUTAN. Haa district: Gakiling block, Gakiling, elev. 842 m, 27.1055°N, 89.1450°E, 10 Oct 2024, P. Gyeltshen, Phuentsho & K. Tobgay 337 (THIM23394 & THIM23397).

Asparagaceae Juss.

5. Peliosanthes maheswariana D.Borah, N.Tanaka & Taram, Adansonia 46: 2, 2024.—TYPE: India. Arunachal Pradesh, West Kameng district, West Kameng, 800–900 m above sea level, 10 Jan 2023, Borah 4045 (ASSAM-not seen) (Fig. 2E).

Terrestrial, perennial herbs. Stem distally erect, proximally creeping and rhizome-like, terete, up to 0.8 cm in diam., green. Leaves 1–2 from annual node; petiole, 10–30 cm long; lamina elliptic or elliptic-lanceolate, 20–40 × 5–10 cm, base attenuate, margins entire, apex acute to acuminate, glabrous, glossy on both surfaces. Inflorescence raceme, flower numerous; peduncle slightly curved near base, up to 17 cm long; rachis 9–15 cm long. Bracts triangular to subulate, 4–23 mm long, green. Flowers solitary, 1.3–1.6 cm across; pedicels, 2–3 mm long; perianth bowl-shaped, distally 6-cleft; proximal syntepalous part flatly saucer-shaped, 3.5–3.8 mm long; segments obliquely spreading, broadly or deltoid-ovate, 4– 6 mm long, 4.5–5 mm wide, apex obtuse to rounded, margin entire. Stamens 6; corona epitepalous, hemispheric or conoid with wall incurved distally, thickened toward base; anthers 6, sessile, ovate, 1.2–1.3 mm long, creamy; pistil 1, c. 3 mm high; ovary almost superior, hemispheric, 1.5 mm high and 3.5 mm wide at base, trilocular; ovules 4 per locule, borne on basal central placenta; style subconic, truncate at apex, 1.5 mm long, 1–1.5 mm wide at base, stigma trisected, 0.8 mm wide. Fruits unknown.

Flowering: December–February.

Distribution: Peliosanthes maheswariana was formerly considered to be endemic to Arunachal Pradesh, India.

Specimens examined: BHUTAN. Sarpang district: Gakidling block, Darachu, elev. 1,400 m, 26.9428°N, 90.2335°E, 12 Jan 2024, P. Gyeltshen & Phuentsho 218 (THIM22782); Chhudzom block, Maukhola, elev. 1436 m, 27.0961°N, 90.3164°E, 22 Jan 2024, P. Gyeltshen & Phuenthso 242 (THIM22839, THIM22840 & THIM22841).

Burmanniaceae Blume

6. Burmannia nepalensis Hook.f., Fl. Brit. India 5: 666, 1888; Gonianthes nepalensis Miers, Trans. Linn. Soc. London 18: 537, 1841.—TYPE: Nepal. 1821, Wallich Cat. 9006 (Photo not seen) (Fig. 2F).

Plants without chlorophyll, holomycotrophic, 4–13 cm tall. Stems whitish, slender. Basal rosette leaves absent; cauline leaves triangular, 2–3.5 × 1 mm. Inflorescences 3–9-flowered; bracts lanceolate, 2–3 mm long. Flowers pedicellate, whitish or yellow; perianth tube 1.5–2.5 mm long; wings conspicuous, 1–2 mm wide; outer tepals oblong-ovate, 0.5–1.2 mm long, margin single; inner tepals orbicular, minute; stamens sessile; connectives with 2 apical crests and a pendent basal spur; ovary subglobose, 1.5–3 mm long. Capsule subglobose; seeds fusiform.

Flowering: July—December.

Distribution and habitat: Burmannia nepalensis is native to Cambodia, China, India, Japan, Laos, Nepal, Philippines, Taiwan, Vietnam and Bhutan (Punakha district; reported here).

Specimen examined: BHUTAN. Punakha district: Guma block, Tsheteyna, elev. 1,654 m, 27.6475°N, 89.7688°E, 17 Nov 2023, P. Gyeltshen, D. D. Lama & K. Rabgay 126 (THIM22561).

Convolvulaceae Juss.

7. Ipomoea triloba L., Sp. Pl. 1: 161, 1753.—TYPE: USA. Icon in Sloane, Voy. Jamaica 1: t. 97, f. 1, 1707 (lectotype: designated by Austin 1978b-photo not seen) (Fig. 2G).

Herb with twining or sometimes prostrate stems, 1–2 m long, sparsely hairy, mainly at the nodes. Leaves, petioles lender, 6–16 cm long, glabrous or sometimes minutely verrucose; lamina hastate in outline, rarely narrower, 3–7.5 × 2–6 cm, deeply 3-lobed, base cordate, margins entire, apex obtuse or acute, adaxial and abaxial surfaces sparsely pilose. Inflorescences axillary, cyme, single or several-flowered; peduncles 1–5 cm long, angular, minutely verrucose towards the apex; bracts minute, lanceolate; pedicels minutely verrucose, up to 10 mm long; sepals glabrous or sparsely hairy, outer sepals oblong, 6–7 mm long, apex obtuse or acute, margins fimbriate; inner sepals elliptic-oblong, apex acute or mucronate; corolla campanulate, 16–18 mm long, glabrous, pale purple; lobes broadly ovate, apex mucronate; stamens included, filaments hairy at the base; ovary hairy. Capsules unknown.

Flowering: September–January.

Distribution: Ipomoea triloba is native to Mexico, Brazil and Caribbean countries and has been introduced in certain tropical and subtropical regions of the world.

Specimens examined: BHUTAN. Sarpang district: Gelephu, Bhur, elev. 400 m, 26.9101°N, 90.4273°E, 11 Jan 2024, P. Gyeltshen & Phuentsho 212 (THIM22770 & THIM22771).

Ebenaceae Gurke

8. Diospyros lanceifolia Roxb., Fl. Ind. (Roxburgh) 2: 537, 1832.—TYPE: Roxburgh’s Plate No. 2508 (Photo not seen) (Fig. 2H).

Tree up to 16 m tall, branchlets appressed sericeous when young, becoming glabrous. Leaves thinly coriaceous; petiole 4–5 mm long; lamina oblong-elliptic 6–14 × 2.5–5 cm, apex acute or shortly acuminate with blunt tip, base cuneate, lateral veins weakly prominent above, obscure beneath. Male flowers usually 3 in short axillary cymes on peduncle 2–7 mm long; calyx 3.5–4 mm long, shortly 4-lobed; corolla sericeous externally, tube 5–7 mm long, lobes 1.8–2 mm long, spreading; stamens 16–18. Females flowers solitary, axillary, sessile; calyx deeply 3–4-lobed, lobes deltoid, 6–10 mm long, 8–12 mm wide, with recurved margins, corolla thick, sericoues externally, tube 7–8 mm long, lobes 3–3.6 mm long, spreading, staminodes 8–12 long, ovary subglabrous, style shortly columner, subtended by enlarged calyx. Fruits globose, 1.8–2.5 × 17–2.4 cm, densely villus outside.

Flowering: April–May.

Distribution: Diospyros lanceifolia is distributed in Bangladesh, Borneo, India, Malaysia, Myanmar, Nepal, Philippines, Sumatra, Thailand, and Bhutan (Tsirang and Zhemgang districts; reported here).

Specimens examined: BHUTAN. Tsirang district: Sergithang block, Gerechu, elev. 900 m, 27.1897°N, 90.0897°E, 2 Dec 2022, P. Gyeltshen 86 (THIM22506 & THIM22507); Zhemgang district: Trong block, Yebilaptsa, elev. 750 m, 27.1399°N, 90.7024°E, 2 Dec 2022, P. Gyeltshen, K. Tobgay, C. Wangmo & Sampa 171 (THIM22672, THIM22673 & THIM22674).

Fabaceae Lindl.

9. Gymnocladus assamicus Kanj. ex P. C. Kanj., Assam Forest Rec., Bot. i. 7, 1934.—TYPE: India. Meghalaya, Khasi Hills, 1920, U.N. Kanjilal 7624 (holotype: ASSAM, 0000000128, Photo!) (Fig. 2I).

Tree 10–13 m tall, bark dark reddish brown, reticulate. Leaves bipinnate, with 7–8 pairs of pinnae, subopposite, pubescent; petiole, 5–6.5 cm long; rachis terete, 35–42.5 cm long; each pinnae 11–24 cm long; leaflets 12–16 pairs on each pinna, minutely petiolulate, alternate, 6–10 mm long, oblong to oblong-ovate, 1.8–3.5 × 0.9–1.3 cm, base rounded, slightly oblique, pubescent on both surfaces, densely on midrib abaxially. Male inflorescence raceme 8–12.5 cm long, purple; calyx 5-lobed, free at the apex, lobes ovate, 6–10 mm long, villous outside, pilose inside; petals 5, free, narrowly ovate, 6–7 mm long; stamens 10, epipetalous, exserted, fertile; filaments short, densely villose; anther lobes oblong, bilobed; pistil rudimentary. Female racemose 3.4–4.6 cm long, purple; calyx 5-lobed, free at the apex, lobes ovate, 6–16 mm long; villous outside, pilose inside; petals 5, narrowly ovate, 6–8 mm long; stamens 10, sterile, epipetalous, exserted; filaments short, densely villose; anthers sterile, lobes 2, globose; style 4–6 mm long, stigma linear, papillate. Pods linear, 12–16 cm × 2.0 – 3.5 cm; transversely ridged and grooved exposing the seeds within, valves fleshy; mesocarp saponaceous; seeds 3– 6-numbered, ovoid or subglobose, 15–17 × 12–15 mm, black; funicle persistent.

Flowering: March–April.

Distribution: Gymnocladus assamicus was formerly considered to be endemic to India (Arunachal Pradesh, Meghalaya and Nagaland). Fig. 1.

Specimens examined: BHUTAN. Lhuentse district: Khoma block, Khariphugoenpa, elev. 2,108 m, 27.6748°N, 91.2439°E, 24 Nov 2024, P. Gyeltshen, K. Tobgay & C. Seldon 466 (THIM22166, THIM22167 & THIM22168).

10. Ormosia robusta (Wight) Voigt, Hort. Suburb. Calcutt. 205, 1845; Sophora robusta Wight, Icon. Pl. Ind. Orient. 1: t. 245, 1839.—TYPE: s.d. (Wight Icones, not seen) (Fig. 3A).

Tree, up to 12 m tall. Stem bark brown, warty, yellowish inside. Young branches densely brownish pubescent. Leaves imparipinnate; petiole 5–7 cm; rachis 8–14.0 cm; leaflets 7– 9; petiolule 5–6 mm long, grooved, brown, pubescent; lamina ovate-lanceolate to oblong-lanceolate, terminal leaflet 15–18 × 4.5–5.5 cm, lateral leaflets 7.0–17 × 2.8–5.5 cm, thinly leathery, base rounded-attenuate, apex acuminate, margin entire, lateral veins 6–13 pairs, glabrous. Inflorescences terminal, 7.0–10.5 cm long; peduncle and pedicel densely rusty pubescent; pedicel 4–6 mm long; bracts linear-lanceolate, 3–4 mm long, densely rusty brown pubescent; bracteoles 2, at pedicel apex, lanceolate, ca. 2 mm long, densely appressed rusty brown pubescent. Flowers creamy-white, 9–12 mm across; calyx persistent, campanulate, 5– 6 mm long; teeth broadly triangular, 2–3 mm long, densely rusty pubescent; corolla orbicular, 6–7 × 5–6 mm when flattened, deeply cucullate; claw short, 1.0–1.5 mm long; wings obovate, 5–6 × 3–4 mm; stamens 10, unequal, all fertile; filaments 6–11 mm long; anthers, ca. 1 mm long. Ovary densely pubescent, 3–4 × 2–2.5 mm; style ca. 4 mm long, densely pubescent at base, apical portion glabrous, curved; stigma introrse, bilobed. Legumes 1–2-seeded, cylindric, 4.5– 8.0 × 2.0–3.0 cm, apex slightly beaked; valves woody, glabrous, yellowish-green. Seeds oblong, ca. 1.8–2.2 × 1.1–1.3 cm, obtuse at ends; testa bright-red; hilum 5–6 mm long.

Flowering: April–June.

Distribution: Ormosia robusta is distributed in Bangladesh, India, Myanmar and Thailand and Bhutan (Pemagatshel district; reported here). Fig. 1.

Specimens examined: BHUTAN. Pemagatshel district: Nganglam, Rinchentsezor, elev. 803 m, 26.8525°N, 91.1460°E, 3 Dec 2023, P. Gyeltshen, K. Tobgay, C. Wangmo & Sampa 194 (THIM22724 & THIM22725).

Gesneriaceae Rich. & Juss.

11. Achimenes longiflora DC., Prodr. 7: 536, 1839.— TYPE: Mexico. Pavon, Sesse and Mocifio, s.n. (holotype: GDC, illustration!) (Fig. 3B).

Herb, 10–40 cm tall, 2–3 mm in diam., green or reddish, villous; branches few. Leaves opposite or 3 at the node; petioles short; lamina ovate or elliptic-lanceolate, 2–6 × 0.6– 3 cm, the apex acute to shortly acuminate, base cuneate to obtuse, sometimes oblique, margin serrate, adaxially green and villous, abaxially pale with reddish between the veins. Inflorescences of single axillary flowers; pedicels 4–5 mm long, densely pilose. Flowers showy; floral tube 4–5 mm long, densely pilose; calyx lobes lanceolate, 7–10 × 2–3 mm long, pubescent, apex acuminate, margin ciliate; corolla lavender, lacking a spur, the tube narrow, 3–5 cm long, glabrous, the limb oblique, broad, flat, 3–5 cm wide, nearly regular, the lobes entire; stamens included, nearly equalling the corolla tube, the filaments adnate to the base of the corolla tube, glabrous; style puberulous, the stigma 2-lobed.

Flowering: May–February.

Distribution and habitat: Achimenes longiflora is native to Colombia, Costa Rica, El Salvador, Guatemala, Honduras, Southeast and Southwest Mexico and Panama and was introduced into Dominican Republic, East Himalayas, Jamaica, Leeward Island, Trinidad & Tobago, Venezuela, and Windward Island. Fig. 1.

Specimens examined: BHUTAN. Chhukha district: Darla block, Arikha, elev. 980 m, 26.8824°N, 89.5911°E, 26 May 2024, K. Tobgay K.ty.535 (THIM23543, THIM23544 & THIM23545); Samtse district: Tendu block, Tendu, elev. 950 m, 27.1062°N, 88.8851°E, 26 May 2024, K. Tobgay 534 (THIM23540, THIM23541 & THIM23542).

Hypericaceae Juss.

12. Hypericum podocarpoides N.Robson, J. Jap. Bot. 52: 276–277, 1977, nom. nov. for H. hookerianum Wight & Arn. var. linearis Banerji, J. Ind. Bot. Soc. 31: 152, 1952.—TYPE: Nepal. Tinpipli to Nepalthoke, 1,000 m above sea level, Banerji 95 (holotype: CAL, Photo not seen) (Fig. 3C).

Erect shrub, 0.5–1.2 m tall. Stem stout, branchlets terete, glabrous. Leaves simple, opposite decussate; petiole sessile; lamina lanceolate or elliptic-lanceolate, 10–78 × 7–17 mm, base broadly cuneate to rounded, margins entire and slightly revolute, apex acute to acuminate, midrib impressed above and prominent beneath, lateral veins about 2–3 on either side of the midrib. Inflorescence terminal cymes or subcorymbs, 3–5-flowered. Flowers 3–6 cm across; pedicel about 1–2.4 cm long, bracts lanceolate, 10–15 × 4–6 mm, apex acute, margins glandular ciliate, sparsely punctate with black glands, caducous; sepals 5, lanceolate-ovate to elliptic, 9–12 × 2.5– 4 mm, apex acute, glandular punctate with black glands, persistent; petals 5, narrow oblanceolate-obovate, 15–23 × 8– 12 mm, yellow or bright yellow, veined prominently, punctate with raised glands; stamens numerous, in bundles or fascicles 5, free, antisepals, filaments linear, 8–12 mm long filiform, glabrous; anthers dorsifixed, yellow or reddish, connectives with usually with black amber gland. Ovary superior, globose, 3 locular, syncarpous, 4.5–6 mm long, ovules numerous, axil placentation; styles 3, 3.6–6 mm long free at the base; stigma 3, capitate. Fruit capsule septicidal, ovoid, 10–12 × 7–10 mm long, apex obtuse, longitudinally vittate, with persistent style.

Flowering: August–October.

Distribution: Hypericum podocarpoides is distributed in China, Nepal, India and Bhutan (Samtse district; reported here). Fig. 1.

Specimens examined: BHUTAN. Samtse district: Samtse block, Tashithang, elev. 1660 m, 26.8948°N, 89.2075°E, 13 Oct 2024, P. Gyeltshen, Phuentsho & K. Tobgay 349 (THIM23416, THIM23417 & THIM23418).

Malvaceae Juss.

13. Grewia serrulata DC., Prodr. 1: 510, 1824.—TYPE: India or Bangladesh. Bengal, 1821, Leschenault s.n. (holotype: G, 00209154, Photo!) (Fig. 3D).

Shrub to small tree, 4–6 m tall; branchlets slender, glabrous. Leaves simple, alternate, distichous; stipules subulate, 6–9 mm long; petiole 5–10 mm long, stellate-pubescent, swollen tipped; lamina elliptic-lanceolate or ovate-lanceolate, 5–18.2 × 1.5–5 cm, base cuneate rounded, apex acuminate or acuminate-caudate, margin serrate, prominently sparsely stellate-pubescent on both sides when young, glabrous when matured, 3 veined at base, lateral veins 4–5 paired. Inflorescence umbellate cyme; peduncles1–2.5 cm long, hairy; flowers bisexual, yellowish-white, 3–5 flowered; pedicel 10–2.3 mm long, hairy; sepals 5, free, 3-nerved; linear, 12–16 mm long, stellate pubescent outside; petals 5, whitish, minute, ovate, ca. 2.5 mm long; stamens numerous; style longer than stamens, stigma fimbriate. Drupes globose, ca. 10 mm diam., glabrous, greenish-black when ripe.

Flowering: July–September.

Distribution: Grewia serrulata is native to the Andaman Islands, Bangladesh, India, Myanmar, Nepal, the Nicobar Islands, Pakistan, Vietnam, and Bhutan (Mongar and Samtse districts; reported here).

Specimens examined: BHUTAN. Mongar district: Saleng block, near Shongarchhu, elev. 1,500 m, 27.28333°N, 91.08333°E, 4 Jul 1979, A.J.C. Grierson & D.G. Long 2461 (E, THIM04811); Samtse district: Pali block, left bank of Chepuwa Khola, elev. 550 m, 26.8502°N, 89.1502°E, 4 Mar 1982, A.J.C. Grierson & D.G. Long 3480 (E, THIM04796); Dumtoe block, Samtse, elev. 950 m, 27.0803°N, 89.1713°E, 12 Oct 2024, P. Gyeltshen, Phuentsho & K. Tobgay 346 (THIM23409, THIM23410 & THIM23411).

14. Sterculia lanceolata Cav., Diss. Decem 6: 287, 1788. Type citation: “Quas olim misit ex China, P. D’Incarville ad D. de Jussieu”; type specimen: not seen (Fig. 3E).

Tree, branches slandered, sparsely stellate. Leaves unlobed, thinly coriaceous; petiole 1.3–3 cm long; lamina elliptic, 5– 19 × 2.8–6 cm, abruptly acuminate, base rounded, margin entire, glabrous. Stipules subulate. Flowers panicles erect, stellate-pubescent 3–7 cm long, red; calyx shortly united at base, lobes oblong 5–10 × 2–3 mm, flat, pubescent outside. Fruit up to 5 scarelet minutely tomentose follicle up to 7 cm, seeds black.

Flowering: March–April.

Distribution: Sterculia lanceolata is native to Bangladesh, Borneo, Cambodia, China, India, Indonesia, Jawa, Laos, Malaysia, Myanmar, Nepal, Thailand, Vietnam and Bhutan (Samdrup Jongkhar district; reported here). Fig. 1.

Specimens examined: BHUTAN. Samdrup Jongkhar district: Orong gewog, Suzung, elev. 650 m, 26.9128°N, 91.4833°E, 15 Apr 2023, K. Tobgay 32 (THIM23527, THIM23528, THIM23529 & THIM23530).

Melastomataceae Juss.

15. Melastoma malabathricum L., Sp. Pl. [Linnaeus] 1: 390, 1753.—TYPE: Sri Lanka. Ceylon, Hermann s.n. (lectotype: BM, 000621418 AND 000621419, designated by Bremer in Jarvis et al. 1993, Photo!) (Fig. 3F).

Busy shrub, up to 3 m tall. Stems 4-sided, and branchlets densely appressed scalelike hairs. Leaves petiole 6–18 mm long; lamina ovate, elliptic, elliptic-lanceolate, 6–14 × 2.5– 4.5 cm, base rounded to subcordate, apex acuminate, 2–5-veined, abaxially densely strigose and puberulous, adaxially densely strigose. Inflorescences corymbose, 1–6-flowered, compact or loose; bracts 2, leaflike from base; pedicels 2.5– 8 mm long, strigose. Flowers hypanthium 4.5–8 mm long, densely appressed strigose, margin fimbriate; calyx lobes lanceolate to ovate-lanceolate, 5–15 mm long, apex acuminate, on both sides and along their margin strigose and pubescent; petals reddish purple, obovate, 20–30 × 10–20 mm. Longer stamens with connective long extended at base, curved, apex bifid; shorter stamens with anthers 2-tuberculate at base; connective not extended. Ovary half inferior, densely strigose, apically with a ring of setae. Fruit globular-urceolate, 5–14 × 6–10 mm, succulent, densely strigose.

Flowering: February–December.

Distribution: Melastoma malabathricum is native to Australia, Borneo, Cambodia, China, India, Indonesia, Japan, Jawa, Laos, Malaysia, Myanmar, Nepal, New Guinea, New South Wales, Philippines, Solomon Island, Sri Lanka, Taiwan, Thailand, Vietnam and Bhutan (Wangdue district; reported here). Fig. 1.

Specimens examined: BHUTAN. Wangdue district: Athang block, Athang, elev. 1269 m, 27.2915°N, 90.1068°E, 30 May 2024, P. Gyeltshen & K. Rabgay 288 (THIM, THIM23426 & THIM23427).

Oxalidaceae R. Br.

16. Biophytum reinwardtii (Zucc.) Klotzsch, in W.C.H.Peters, Naturw. Reise Mossambique 6 (Bot., 1): 85, 1861; Oxalis reinwardtii Zucc., Abh. Math.-Phys. Cl. Königl. Bayer. Akad. Wiss. 1: 274, 1829.—TYPE: Indonesia. Java, 1825, Reinwardt s.n. (syntype: M, 0172355, Photo!) (Fig. 3G).

Stem 8–16 cm tall, pubescent. Leaves crowded at the apex of stem, 9–20 in whorl; rachis ending in short subulate point; leaflets 6–12 pairs; terminal pairs largest, obovate, 7–13 × 4– 7 mm, base oblique, apex apiculate, glabrous; leaflets oblong, 4–10 × 2–6 mm, symmetric, basal leaflets broadly ovate, 1– 2 mm long; petiole 1–2 cm, pubescent. Inflorescence umbel cyme, 4–6-flowered; peduncle 2–5.5 cm long, hairy; pedicel 3–5 mm long; bracts ca. 1 mm long; sepals 2–3 mm long, 4– 8 veined; petals elliptic, 6–8 mm long, yellow. Capsules 2–3 × 2 mm, with separate gland-tipped hairs.

Flowering: September–March.

Distribution: Biophytum reinwardtii is native to Bangladesh, Cambodia, China, India, Indonesia, Malaysia, Myanmar, Nepal, New Guinea, Philippines, Thailand and Bhutan (Chhukha and Dagana districts; reported here). Fig. 1.

Specimens examined: BHUTAN. Dagana district: Lhamoizingkha block, Near Oyster lake, elev. 248 m, 26.7239°N, 89.8068°E, 15 Oct 2024, P. Gyeltshen, Phuentsho & K. Tobgay 355 (THIM, THIM20042); Chhukha district: Phuntsholing block, right bank of Kharbandi, elev. 356 m, 26 51’28.1’’N, 89 23’22.3’’E, 19 Aug 2012, S. Tshering 161 (THIM03941, THIM03942, THIM03943 & THIM03944).

Phyllanthaceae Martinov

17. Breynia macrantha (Hassk.) Chakrab. & N.P.Balakr., Bangladesh J. Pl. Taxon. 19: 121 (2012); Sauropus macranthus Hassk., Retzia 1: 166 (1855).—TYPE: Indonesia. Hortus Bogoriensis, Teijsmann s.n. (holotype: L, 0138428, Photo not seen) (Fig. 3H).

Shrub 3–4 m tall, glabrous, branchlets angular. Stipules subulate-lanceolate, 3–6 mm, gray-brown; petiole 2.5–7 mm; lamina chartaceous, ovate-elliptic or elliptic-lanceolate, 4–20 × 3.5–8 cm, base cuneate or rounded, apex shortly acuminate, conspicuously white-margined; venation pinnate, lateral veins 6–10-paired. Inflorescence axillary, 1-flowered or several male and female per cluster. Male flower pedicels 2–6 mm long; calyx discoid, 3.5–4.7 mm in diam., shallowly 6–8-fid, with red stripes; sepals triangular. Female flowers solitary or several and male mixed in axillary cluster; pedicels 2–6 cm long; calyx yellow-green, 6-lobed; sepals slightly thick, biseriate, outer obovate or ovate-elliptic, 6–7 × 3–4 mm; inner shorter, obovate, ca. 5 mm long, with purple stripes; disk absent; pistil depressed globose, ca. 2 × 2.7 mm, 3-locular; styles 3, bifid at apex, arms recurved. Fruiting pedicel 9–13 cm long; capsules subglobose, ca. 1.5 × 1.5–2.5 cm, red or red-brown, styles persistent at apex.

Flowering and fruiting: May–January.

Distribution: Breynia macrantha is distributed in Australia, China, India, Indonesia, Laos, Malaysia, Myanmar, Philippines, Thailand, Vietnam and Bhutan (Pemagatshel district; reported here). Grierson and Long (1987) included this species in the Flora of Bhutan under its basionym, Sauropus macranthus, from the Darjeeling Terai of West Bengal.

Specimens examined: BHUTAN. Pemagatshel district: Nganglam, elev. 374 m, 26.8141°N, 91.2583°E, 4 Dec 2023, P. Gyeltshen, K. Tobgay, C. Wangmo & Sampa 198 (THIM22737 & THIM22738).

18. Bridelia assamica Hook.f., Fl. Brit. India 5: 269, 1887.—TYPE: India. Assam, 1850, Griffith 1238 (lectotype: K, 000246269, designated by Chakrabarty & Balakrishnan, 2018, Photo!) (Fig. 3I).

Shrub or tree 2.5–5 m tall. Branchlets hairy when young, and becoming glabrescent. Leaves stiffly chartaceous; petioles 5–10 mm long, pilose; lamina elliptic or oblanceolate, 5.8–32 × 4.5–8 cm, base sub-cuneate, apex acuminate or caudate, margin entire, adaxially glabrous, densely pilose abaxially, lateral nerves 10–18-paired, terminating directly at the margins into the marginal veins. Inflorescences borne on the main leafy branches, ca. 6 mm in diam.; bracts broadly ovate, ca. 0.4 mm long. Flowers not seen. Fruits sessile, broadly ovoid to ellipsoid, 8.5–10 × 5–6.5 mm, glabrous, 1-locular, black when dry; style beak ca.1 mm long; sepals triangular, 2.3–2.5 × 1– 1.2 mm, glabrous; seed with a longitudinal groove.

Flowering: November–January.

Distribution: Bridelia assamica is native to Bangladesh, India, and Bhutan (Samdrup Jongkhar district; reported here).

Specimens examined: BHUTAN. Samdrup Jongkhar district: Jomotsangkha, Kherkheri, elev. 484 m, 26.9009°N, 91.9589°E, 9 Apr 2023, K. Tobgay & Sampa 258 (THIM23531, THIM23532, THIM23533 & THIM23534).

Verbenaceae J. ST.-Hil.

19. Lippia alba (Mill.) N. E. Br. ex Britton & P. Wilson, Sci. Surv. Porto Rico & Virgin Islands 6: 141, 1925; Lantana alba Mill., Gard. Dict. (ed. 8) Lantana No. 8, 1768. Type citation: “Camara foliis urticae, floribus minoribus albis, ex alis foliorum prodeuntibus. Houst,” type specimen: not seen. Fig. 4.

Small aromatic subshrub, 1–1.6 m tall. Stems ribbed, whitish tomentose. Leaves opposite, lemon scented when crushed, finely rugose; petiole 5–10 mm long; lamina ovatelanceolate 3–7 × 2–4 cm, base cuneate, apex acute, margin crenate-serrate, 3-veined at base, hairy on both surfaces. Inflorescence dense subglobose or cylindric heads, 7–15 cm long, flowers fragment; peduncles 1–1.5 cm long, villous; bracts ovate, 3–4 mm long, villous; calyx 2-lobed, almost to base, lobes c. 1.2–1.4 mm long; corolla pink, tube narrow, 3– 3.5 mm long; lip large, 1.8–2 mm long, side lobes 6–7 mm long. Fruits depressed globose, 2–2.2 mm diam., with persistent appressed calyx lobes.

Flowering: October–June.

Distribution: Lippia alba is native to Central and South America, but it is introduced in Australia, Bangladesh, India, Portugal, and Bhutan (Sarpang district; reported here).

Specimens examined: BHUTAN. Sarpang district: Umling block, Gadhen, elev. 200 m, 26.8330°N, 90.5290°E, 26 May 2024, K. Tobgay 635 (THIM23546, THIM23547, THIM23548, THIM23549 & THIM23549).

CONCLUSION

Nineteen plant species, Achimenes longiflora, Biophytum reinwardtii, Breynia macrantha, Bridelia assamica, Burmannia nepalensis, Ceropegia khasiana, Diospyros lanceifolia, Goniothalamus sesquipedalis, Grewia serrulate, Gymnocladus assamicus, Hypericum podocarpoides, Ipomoea triloba, Lippia alba, Melastoma malabathricum, Ormosia robusta, Peliosanthes maheswariana, Phlogacanthus curviflorus, Sterculia lanceolata and Vincetoxicum belostemma are discussed and reported as new records to the Flora of Bhutan. Of these, A. longiflora, I. triloba and L. alba are exotic, while the remaining species are native to the country. Most of the species are collected from the subtropical and warm broadleaved forests in the central and southern parts of the country. Based on current trends in botanical research and past exploration efforts, we strongly recommend undertaking more comprehensive and systematic surveys across various regions of Bhutan. These surveys will not only deepen our understanding of the country’s unique flora but will also contribute to its conservation efforts.

NOTES

ACKNOWLEDGMENTS

The authors thank the Director and staff of the Department of Forest and Park Services for providing collection permission and the necessary support. We also extend our gratitude to the staff of the National Biodiversity Centre for providing research facilities and support. The study travel (as professional services) was supported by the Royal Government of Bhutan (RGoB).

CONFLICTS OF INTEREST

The authors declare that there are no conflicts of interest.

Fig. 1

Map of the research area and the collection sites. Locations of the newly reported species are indicated by numerals, which also correspond to the species numbers in this paper.

Fig. 2

New records of flowering plants for the flora of Bhutan. A. Phlogacanthus curviflorus (Wall.) Nees (Acanthaceae). B. Goniothalamus sesquipedalis Hook. f. & Thomson (Annonaceae). C. Ceropegia khasiana Murug. (Apocynaceae). D. Vincetoxicum belostemma. E. Peliosanthes maheswariana D.Borah, N.Tanaka & Taram (Asparagaceae). F. Burmannia nepalensis Hook.f. (Burmanniaceae). G. Ipomoea triloba L. (Convolvulaceae). H. Diospyros lanceifolia Roxb. (Ebenaceae). I. Gymnocladus assamicus Kanjilal ex P.C.Kanjilal (Fabaceae).

Fig. 3

New records of flowering plants for the flora of Bhutan. A. Ormosia robusta (Wight) Voigt (Fabaceae). B. Achimenes longiflora DC. (Gesneriaceae). C. Hypericum podocarpoides N. Robson (Hypericaceae). D. Grewia serrulata DC. (Malvaceae). E. Sterculia lanceolata Cav. (Malvaceae). F. Melastoma malabathricum L. (Melastomataceae). G. Biophytum reinwardtii (Zucc.) Klotzsch (Oxalidaceae). H. Breynia macrantha (Hassk.) Chakrab. & N.P.Balakr. (Phyllanthaceae). I. Bridelia assamica Hook.f. (Phyllanthaceae).

Fig. 4

New records of flowering plants for the flora of Bhutan: Lippia alba (Mill.) N. E. Br. ex Britton & P. Wilson (Verbenaceae).

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