Checklist to the Elatostema (Urticaceae) of Vietnam including 19 new records, ten new combinations, two new names and four new synonyms

Elatostema (Urticaceae) comprises several hundred herbaceous species distributed in tropical and subtropical Africa, Asia, Australia and Oceania. The greatest species richness occurs on limestone karst in Southeast Asia. Taxonomic revisions of Elatostema are largely out of date and contradict each other with respect to the delimitation of Elatostema and Pellionia. Most herbaria in SE Asia and worldwide contain significant amounts of unidentified material. As part of a broader revision of Elatostema in SE Asia, we present an updated checklist for Vietnam based on field visits, a review of specimens in herbaria worldwide, a review of type material and nomenclature. We recognize 77 taxa (75 species and two infraspecific taxa) of Elatostema in Vietnam, 23 of which were previously ascribed to Pellionia. Nineteen of these are new records for the country, i.e., E. attenuatoides, E. austrosinense, E. backeri, E. brunneinerve, E. crassiusculum, E. crenatum, E. fengshanense, E. glochidioides, E. malacotrichum, E. nanchuanense, E. oblongifolium, E. obtusum, E. oppositum, E. pergameneum, E. prunifolium, E. pseudolongipes, E. pycnodontum, E. salvinioides and E. xichouense. We place E. baviensis in synonymy of E. platyphyllum, E. colaniae in synonymy of E. myrtillus, P. macroceras in synonymy of E. hookerianum, and P. tetramera in synonymy of E. dissectum for the first time. Fourteen taxa (18% of all the recognized taxa) are endemic to Vietnam, which makes Elatostema one of the richest genera for endemic species in this country; this level of endemism is comparable to levels observed in Orchidaceae. Our checklist suggests that the highest diversity and endemism of Elatostema occurs in northern Vietnam, and that there is the greatest floristic similarity of northern Vietnam to SW China. The relationship among floristic regions is also investigated. We could find no records of Elatostema for 33 out of 63 provincial units of Vietnam, including all the southernmost provinces. We propose that further studies on the diversity of Elatostema in central and southern Vietnam are severely needed

Chiloschista pulchella (Orchidaceae: Aeridinae) new orchid species from Lao PDR

The new species, Chiloschista pulchella (Orchidaceae: Aeridinae) was discovered in Hin Nam No Nature Protected Area, Khammoune Province of the central Laos. The paper provides detailed description and illustration of this species, which is identified as a local endemic of karstic rocky limestone of the northern part of the protected area. It differs from all known congeners in the thin lip, median lip lobe dissected into two small subulate lobules, as well as in large purple blotches on the lip side-lobes never found in other species of this genus. The newly discovered plant represents interest for cultivation as an ornamental plant and needs protection in its natural habitats

Leptomischus hiepii, a new species of Rubiaceae from Vietnam

Leptomischus hiepii, a new species of the tribe Argostemmateae from Son La province, northwestern Vietnam, is described and illustrated. Morphologically it allies to L. wallichii, L. erianthus and L. funingensis by sharing a similar habit, large stipules and similar corolla shape, but it differs by its anisophyllous leaves, 1-flowered inflorescences, homostylous flowers and tubular-campanulate corollas

Leptomischus hiepii, a new species of Rubiaceae from Vietnam

Leptomischus hiepii, a new species of the tribe Argostemmateae from Son La province, northwestern Vietnam, is described and illustrated. Morphologically it allies to L. wallichii, L. erianthus and L. funingensis by sharing a similar habit, large stipules and similar corolla shape, but it differs by its anisophyllous leaves, 1-flowered inflorescences, homostylous flowers and tubular-campanulate corollas

Checklist of the genus Ridsdalea (Rubiaceae, Gardenieae) in Vietnam with description of the new species R. backanensis

The paper provides an identification key and an annotated list of all six species of the genus Ridsdalea J.T.Pereira & K.M.Wong (Rubiaceae, Gardenieae) recorded in the flora of Vietnam, along with data on their valid names, synonyms, types, and distribution. A new species, R. backanensis, discovered in the limestone area of Bac Kan Province (northern Vietnam), is described and illustrated. Detailed data on its characters, ecology, distribution, phenology, preliminary IUCN conservation status, and taxonomical notes are given. The newly discovered species is potentially interesting for cultivation as an ornamental tree that may be effectively used in garden and urban green architecture

Bulbophyllum sect. Hirtula in eastern Indochina

Modern taxonomic revision of Bulbophyllum sect Hirtula in the flora of eastern Indochina, including Cambodia, Laos and Vietnam based on all available collections and literature data reports 12 species (Bulbophyllum clipeibulbum, B. dasystachys, B. glabrichelia, B. nigrescens, B. nigripetalum, B. parviflorum, B. penicillium, B. phitamii, B. scaphiforme, B. secundum, B. setilabium, B. spadiciflorum), 2 of which represent new records for the studied flora (B. parviflorum, B. penicillium) and 3 (Bulbophyllum glabrichelia, B. phitamii, B. setilabium) are described as a new for science. For all accepted taxa the paper provides valid name and main synonyms with appropriate standard taxonomic references, data on type and other authentic materials, description, data on ecology, phenology, expected conservation status, distribution, notes on biology and taxonomy, list of all studied materials, as well as key for identification of species and their line and color illustrations

Loropetalum flavum (Hamamelidaceae), a new species from northern Vietnam

Loropetalum flavum (Hamamelidaceae) is described and illustrated as a new species from Bat Dai Son Mountains situated in the northern Vietnam. Recently discovered plant was observed as a typical element of the rich primary forest found on the highly eroded karstic limestone mountain formations allied to the border with China. The new species is characterized by arboreous habit; stellately indumentum of branchlets, leaves and flowers; axillary, capitate, 4–12-flowered inflorescences; yellow, sessile, actinomorphic, bisexual, 4–6-merous flowers with 2-whorled perianth and 2–8 fleshy disc lobes; stamens with conspicuous subulate connective protrusion; anthers with 2 rectangular 2-sporangiate thecae, each dehiscing by 2 valves and syncarpous gynoecium with 2-locular inferior ovary bearing 2 very short separate styles. A key to all known species of Loropetalum species is given and lectotype of L. lanceum is proposed

Hoya phuwuaensis Kidyoo. A, B. Flattened 2016

<i>Hoya phuwuaensis</i> Kidyoo (2016: 218). <p> <i>H.</i> sect. <i>Peltostemma</i> Schlechter (1916: 14)</p> <p>(Fig. 3).</p> <p> <b>Type</b>:— THAILAND. Phu Wua Wildlife Sanctuary, Bueng Kan Province, 200 m, 2008, <i>M. Kidyoo 1035</i> (holotype BKF, isotype BCU, not seen, fide Kidyoo 2016).</p> <p> <b>Description</b> (based on specimens from Vietnam):—Slender creeping epiphytic herbaceous vine to 2 m long with pure white latex in all vegetative parts. <b>Stem</b> terete, 2–2.5 mm in diameter, pale gray brown, scabrous; internodes (2.5)3–6(7) cm long. <b>Leaves</b> shortly petiolate; petiole gray brown, scabrous, (3.5)4–7(8) mm long, (1.8)2–2.2(2.5) mm in diameter; leaf blade thick, coriaceous, elliptic, acute, base cuneate, scabrous, (5.5)6–9(11) cm long, (1.8)2– 3(3.2) cm wide, margins entire to slightly undulate, wrinkled, or revolute; adaxial surface dark grassy dark green with large, irregular white blotches; abaxial surface uniformly light pale green; median and lateral veins almost invisible. <b>Inflorescence</b> extra-axillary, pendulous, 20–28-flowered umbelliform raceme; peduncle slender, dirty purple brown, (4.5)5–5.5(6) cm long, scabrous; rachis perennial, fleshy. <b>Pedicels</b> of the peripheral flowers 1.4–1.5 cm long, light pinkish to almost white. <b>Calyx</b> persistent, deeply 5-lobed, lobes white to pinkish, narrowly ovate, obtuse, 1.4–1.6 mm long, scabrous outside. <b>Corolla</b> discoid, with 5 broadly triangular lobes, white, 0.8–1.2 cm in diameter; adaxial surface densely pubescent with long straight hairs along the margins of the lobes; abaxial surface glabrous; lobes reflexed, distally revolute, 3.2–4 mm long, apex acute. <b>Corona</b> purple red, 4.8–5 mm in diameter; outer angle of corona lobe narrowly ovoid, 2–2.2 mm long, almost straight or distally slightly up-cured, with round apex, upper surface convex; inner angle of corona lobes erect, narrowly conoid, acute, 1.3–1.4 mm tall, much higher than outer angles. <b>Anther appendages</b> yellow with a white apical part, erect, narrowly triangular, acute, 0.8–1 mm long, exceeding the apex of inner corona angles. <b>Pollinarium</b> about 0.3 mm long; pollinia pale yellow, obliquely oblong, 0.3–0.31 mm long, narrowly winged, truncate, margins pellucid; caudicles short, hyaline, with broad wing, light pale yellow; translators, pale yellow, obscurely triangular; corpusculum brown, obtriangular, laterally compressed. <b>Pistil</b> dull pink, about 1 mm long, of two separate, glabrous, wine bottle shaped ovaries. <b>Stigma head</b> white, broadly conoid, 0.7–0.8 mm tall and wide. <b>Fruits</b> not seen.</p> <p> <b>Habitat and phenology</b>:—Epiphyte on tall trees in broad-leaved evergreen mountain forests, commonly along stream valleys, often on <i>Ficus</i> sp. Flowers in May.</p> <p> <b>Distribution</b>:— Vietnam, Dak Lak Province (Lak District, Chu Yang Sin Mountains). NE Thailand (Bueng Kan Province, Phu Wua Wildlife Sanctuary).</p> <p> <b>Conservation status:</b> —In Vietnam, only one small population of this rare species has been discovered until now. It was found in an area affected by occasional deforestation, seriously impacting habitat quality. The species may also be threatened in the future by commercial collecting. Additionally, a very small area of the occurrence and occupation identifies conservation species status as Nationally Critically Endangered (nationally CR), following the formal criteria proposed by UIUCN (2022) as follows:A3c,d; B1a,b(i–iii,v)+2a,b(i–iii,v); C1+2(i,ii); D1;—population reduction suspected to be met in the future (A3), a decline in area of occupancy (AOO), extent of occurrence (EOO), and habitat quality (c), and actual or potential levels of exploitation (d);—the area of occurrence <100 km ² (B1) and the area of occupancy <10 km ² (B2), with 1 known population (a) and continuing observed decline of extent of occurrence (bi); the area of occupancy (bii); area, quality of habitat (biii); the number of mature individuals (bv);—the number of mature individuals <250, estimated or projected continuing decline in 25% in 3 years or 1 generation (C1), and observed, estimated, projected or inferred continuing decline when the number of mature individuals in each subpopulation (C2(i)) ≤ 50 and % of mature individuals in one subpopulation = 90–100% (C2(ii));—the number of mature individuals <50 (D). The discovered population of this species in Vietnam is distant from its alone early-known location in NE Thailand, more than 800 km to the SE. According to available information, the species may already be extinct from nature in Thailand (Kydoo 2016), and the Vietnamese population represents currently the only natural refugium of this remarkable taxon in nature.</p> <p> <b>Note</b>:—The species is easy to cultivate and remarkable for its beautiful flowers and white-green tessellated leaves. The plant has good prospects for cultivation as an ornamental plant.</p> <p> <b>Studied specimens</b>:— Vietnam, Dak Lak Province, Lak District, Chu Yan Sin Mountains, epiphyte on <i>Ficus</i> sp., 16 September 2021, <i>Truong Ba Vuong & Nguyen Van Canh, BV 1667</i> (VNM 00043091, photos—LE 01124052 https://en.herbariumle.ru/?t=occ&id=165926). Vietnam, Dak Lak Province, Lak District, herbarium prepared from cultivated plants by Nguyen Van Canh <i>s.n.</i> in May 2022, det.: May 2022, <i>Nguyen Van Canh, AL 1397</i> (LE 01169047 https://en.herbariumle.ru/?t=occ&id=140563).</p>Published as part of <i>Nguyen, Van Canh, Averyanov, Leonid V., Nguyen, Quoc Bao, Dang, Van Son, Nguyen, Van Khuong, Maisak, Tatiana V. & Truong, Ba Vuong, 2023, A new species, Hoya honglenae and the first report of H. acuminata and H. phuwuaensis (Apocynaceae, Asclepiadoideae) in the flora of Vietnam, pp. 60-68 in Phytotaxa 632 (1)</i> on pages 65-67, DOI: 10.11646/phytotaxa.632.1.5, <a href="http://zenodo.org/record/10435180">http://zenodo.org/record/10435180</a&gt

Hoya honglenae Aver., Vuong, Bao & V. C. Nguyen. A, B. Flattened 2023, sp. nov.

<i>Hoya honglenae</i> Aver., Vuong, Bao & V.C.Nguyen, <i>sp. nov.</i> <p> <i>H.</i> sect. <i>Peltostemma</i> Schlechter (1916: 14)</p> <p> <b>(</b> Fig. 2).</p> <p> <b>Diagnosis</b>:—The new species differs from the morphologically closest <i>Hoya phuwuaensis</i> in the usually entire, straight leaf margin rarely slightly undulate (vs. leaf margin wrinkled and somewhat revolute), leaf blade sparsely white speckled adaxially and dirty purple speckled abaxially (vs. leaves with large white blotches all over the adaxial surface and uniform light green abaxially), corolla yellow to pale yellow orange, 6–7 mm in diameter (vs. corolla white, 8–12 mm in diameter), oblong-conoid, obtuse, distinctly up-curved outer angle of corona lobes (vs. outer angle narrowly ovoid, round at apex, not up-cured), and oblong, truncate to obtuse anther appendages 1–1.2 mm long (vs. anther appendages triangular, acute, 0.8–1 mm long).</p> <p> <b>Type:</b> — VIETNAM. Kien Giang Province: Phu Quoc Island, herbarium prepared from plants cultivated in Buon Ma Thuot Town (Dak Lak Province of southern Vietnam) in June 2021, by <i>Nguyen Van Canh, AL 1399</i> (LE 01169050 https://en.herbariumle.ru/?t=occ&id=140570, authentic photos—LE 01124053 https://en.herbariumle.ru/?t=occ&id=165927).</p> <p> <b>Paratypes</b>:— VIETNAM. Kien Giang Province: Phu Quoc Island, herbarium prepared from cultivated plants in June 2021, by <i>Nguyen Van Canh, AL 1400</i> (LE 01169051 https://en.herbariumle.ru/?t=occ&id=140569). VIETNAM. Kien Giang Province: Phu Quoc Island, lowland forest around Cua Duong Commune, epiphyte, 11 December 2022, <i>Truong Ba Vuong, Nguyen van Canh & Nguyen Quoc Bao, BV 1668</i> (VNM 00043090).</p> <p> <b>Etymology:</b> —The species is named after Mrs. Nguyen Thi Hong Len, who found it in nature and kindly shared the specimens to study.</p> <p> <b>Description:</b> —Slender creeping epiphytic herbaceous vine 3–4 m long with white to yellowish white latex in all vegetative parts. <b>Stem</b> terete, 3–4 mm in diameter, greenish brown to gray, verrucose, with stiff sparse hairs; internodes 3.5–10 cm long. <b>Leaves</b> shortly petiolate; petiole stout, black, 5–6 mm long, 3 mm in diameter, densely bristle; leaf blade thick, rigid, coriaceous, narrowly ovate to elliptic, acute, 5.5–6 cm long, 2.5–3 cm wide, almost glabrous, or with sparse, very short strigose hairs, base broadly cuneate to almost round, nerves inconspicuous on both sides, margin entire or slightly undulate, adaxial surface dark grassy green with irregular white and dirty purple brownish marks, abaxial surface pale green with many dirty purple violet speckles. <b>Inflorescence</b> extra-axillary, pendulous, umbelliform raceme, slightly concave in outline, normally bearing 8–20(22) flowers; peduncle terete, slender, down directed, 3.5–4.5 cm long, 0.9–1.2 mm in diameter, straight to slightly curved, scabrous; rachis perennial, fleshy, terete, gray brown, 0.8–1.4 cm long, 3–3.5 mm in diameter, bearing flowers at apex; flower buds broadly conoid, pentagonal; flowers widely opening, almost flat. <b>Pedicels</b> white, sometimes with a purple tint, about 0.8 mm in diameter, in peripheral flowers 1–1.2 cm long, at the center of inflorescence 7–9 mm long, somewhat verruculose. <b>Calyx</b> persistent, deeply 5-lobed; lobes pale pinkish, narrowly triangular ovate, about 1 mm long, 0.5 mm wide, acute to obtuse, adaxial surface glabrous, abaxial surface scabrous. <b>Corolla</b> discoid, with 5 broadly triangular lobes, yellow to pale yellow orange, 6–7 mm in diameter; adaxial surface densely pubescent with long white stiffy hairs; abaxial surface glabrous; connate part 1–1.2 mm long; lobes distally revolute, 3–4 mm long, apex triangular acute. <b>Corona</b> purple to dark purple, 5 lobed, 3–4 mm in diameter; outer angle of corona lobe oblong-conoid, 1.4–1.6 mm long, distally up-cured, with obtuse apex, upper surface convex, lower sulcate; inner angle of corona lobe erect, narrowly conoid, acute, 1.1– 1.3 mm tall, much higher than outer angles. <b>Anther appendages</b> yellow with white apical part, oblong to triangular oblong, 1–1.2 mm long, 0.2–0.3 mm broad, erect, truncate, much longer than apex of inner corona angles, covering the stigma head. <b>Pollinarium</b> about 0.4 mm long; pollinia light yellow, obliquely oblong, narrowly winged, 0.32–0.34 mm long, apex of pollinia truncate, margins pellucid; caudicles stout, short, hyaline, with broad deltoid wing, light pale yellow; translators, pale yellow, obscurely triangular; corpusculum brown, ovate, obtriangular, laterally compressed. <b>Pistil</b> white to light pink, about 1 mm long, of 2 separate, glabrous, wine bottle shaped ovaries. <b>Stigma head</b> white, broadly conoid, about 0.8–0.9 mm tall and wide. <b>Fruits and seeds</b> not seen.</p> <p> <b>Habitat and phenology:</b> —Dry lowland evergreen broad-leaved forests, commonly under canopies of tall trees at elevation 50–150 m a.s.l. Flowers in June.</p> <p> <b>Distribution:</b> — Vietnam, Kien Giang Province (Phu Quoc Island). Endemic.</p> <p> <b>Conservation status:</b> —The described plant was observed as an uncommon epiphytic vine in a single location. This species’ habitat has remained untouched until now, but the plant may face commercial collecting in the future. Additionally, a small number of mature plants in a single population with a very small area of occurrence and occupation identify preliminary species status as Globally Critically Endangered (Globally CR), following the formal criteria of the IUCN (2022) as follows: B1a,b(v)+2a,b(v); C1+2(i,ii); D1—the area of occurrence <100 km ² (B1) and the area of occupancy <10 km ² (B2), with 1 known population (a);—the number of mature individuals <250, estimated or projected continuing decline in 25% in 3 years or 1 generation (C1), and estimated, projected or inferred continuing decline when the number of mature individuals in each subpopulation (C2(i)) ≤ 50 and % of mature individuals in one subpopulation = 90–100% (C2(ii));—the number of mature individuals <50 (D).</p> <p> <b>Note</b>:—Among morphologically similar Indochinese species of the section <i>Peltostemma</i>, such as <i>H. phuwuaensis</i> Kidyoo (2016: 218), <i>H. caudata</i> Hooker (1883: 60), and <i>H. soidaoensis</i> Kidyoo (2013: 45), our species is most close to <i>H. phuwuaensis</i>. Segregating morphological characters of related species are presented in Table 1.</p> <p> Data on morphological characters of <i>Hoya phuwuaensis</i>, <i>H. caudata</i>, and <i>H. soidaoensis</i> are compiled from the literature sources (Kidyoo 2013, 2016, Middleton & Rodda 2019).</p>Published as part of <i>Nguyen, Van Canh, Averyanov, Leonid V., Nguyen, Quoc Bao, Dang, Van Son, Nguyen, Van Khuong, Maisak, Tatiana V. & Truong, Ba Vuong, 2023, A new species, Hoya honglenae and the first report of H. acuminata and H. phuwuaensis (Apocynaceae, Asclepiadoideae) in the flora of Vietnam, pp. 60-68 in Phytotaxa 632 (1)</i> on pages 62-65, DOI: 10.11646/phytotaxa.632.1.5, <a href="http://zenodo.org/record/10435180">http://zenodo.org/record/10435180</a&gt

Hoya acuminata Hook. f.

<i>Hoya acuminata</i> (Wight) Benth. ex Hook.f. in Hooker (1883: 53). <p> <i>H.</i> sect. <i>Pterostelma</i> Hooker (1883: 53).</p> <p>(Fig. 1).</p> <p> ≡ <i>Pterostelma acuminatum</i> Wight (1834: 39).</p> <p> <b>Type:</b> — BANGLADESH. Silhet: Wall Asclep 129, <i>Wallich 8170 Pterostelma acuminata</i> (lectotype K000438717 photo!, designated by Rodda <i>et al.</i>, 2019, isolectotype E00179581 photo!).</p> <p> <b>Description</b> (based on specimens from Vietnam):—Epiphytic, entirely glabrous undershrub to 0.8 m tall without white latex. <b>Stem</b> terete, glossy green, sub-scandent or pendulous, 2–2.5 mm in diameter; internodes (4.5)5–7(8) cm long. <b>Leaves</b> grassy green, shortly petiolate; petiole (3)3.5–5.5(6.5) mm long, (1.4)1.6–2(2.2) mm in diameter; leaf blade rather thin, leathery, oblong narrowly ovate, acuminate, base cuneate to almost round, (5)6–10(11) cm long, 1.5–2.5 cm wide, margins entire to slightly undulate, with prominent median vein and 3–5 rather obsure lateral veins from each side. <b>Inflorescence</b> terminal or extra-axillary, pendulous, (3)4–5(6)-flowered umbelliform raceme; peduncle slender, glossy green, (1.8)2–2.5(2.8) cm long. <b>Pedicels</b> (2.2)2.5–3.2(3.8) cm long, dull pinkish. <b>Calyx</b> persistent, deeply 5-lobed, lobes dull pinkish to pale greenish, oblong lanceolate, obtuse, 4–5 mm long, 0.8–1 mm wide, glabrous. <b>Corolla</b> with 5 white, acute, narrowly triangular, puberulous, reflexed back lobes, (1.6)2.8–2(2.2) cm long, joined near the base into a short tube 2.2–2.4 mm long, 6–7 mm in diameter, puberulous within. <b>Corona</b> glossy, hyaline, white or very light yellowish pink, 5.5–6 mm in diameter; outer angle of corona lobe flattened from sides, obscurely rectangular, about 2 mm wide and 3 mm tall; inner angle of corona lobes in form of erect, subulate, acute, processus, twice exceeding anther appendages. <b>Anther appendages</b> yellow with a white apical part, erect, narrowly oblong, truncate, about 4 mm long, distinctly shorter than inner corona angles. <b>Pollinarium</b> about 1 mm long; pollinia pale yellow, oblong; caudicles short, hyaline, pale yellow; translators pale yellow; corpusculum purple brown, elliptic. <b>Pistil</b> dull pink, about 2.5 mm long, of two separate, glabrous, wine bottle shaped ovaries. <b>Stigma head</b> white, broadly conoid. <b>Fruit and seeds</b> not seen.</p> <p> <b>Habitat and phenology:</b> —Submontane evergreen broad-leaved forests at elevations about 1000 m a.s.l., very rare. Flowering in February–March.</p> <p> <b>Distribution:</b> — Vietnam (Lai Chau Province). Bhutan, Bangladesh (Sylhet), NE India (Meghalaya, Sikkim), W China (Tibet), Myanmar (Gui <i>et al.</i> 2017, Rodda <i>et al.</i> 2019).</p> <p> <b>Conservation status:</b> —A very rare species that has been known in Vietnam until now from a single location in the extreme northwest part of the country, near the Laotian border. Taking into consideration the very small area of its occurrence in Vietnam, wide regional deforestation, and commercial collecting, the conservation status of this species may be preliminary estimated as Nationally Critically Endangered (Nationally CR) following to formal criteria proposed by IUCN (2022) as following: A2a–c; B1a,b(i–iii,v)+2a,b(i–iii,v); C1+2(i,ii); D1;—expected population reduction for 10 years or 3 generation ≥ 80% are not reversible (A2), based on direct observation (a), observed decline of the area of occupancy, extent of occurrence and habitat quality (b), and actual levels of exploitation (c);—the area of occurrence <100 km ² (B1) and the area of occupancy <10 km ² (B2), with 1 known population (a) and continuing observed decline of extent of occurrence (bi); the area of occupancy (bii); area, quality of habitat (biii); the number of mature individuals (bv);—the number of mature individuals <250, estimated or projected continuing decline in 25% in 3 years or 1 generation (C1), and observed, estimated, projected or inferred continuing decline when the number of mature individuals in each subpopulation (C2(i)) ≤ 50 and % of mature individuals in one subpopulation = 90–100% (C2(ii));—the number of mature individuals <50 (D).</p> <p> <b>Notes</b>:—The discovery of this species in Vietnam essentially expands its known area to the east by at least 500 km. Specimens from Vietnam as well as plants known from Myanmar and Tibet differ from the type in distinctly longer peduncles 1.8–2.8 cm long (vs. 1.2 cm), longer pedicels 2.2–3.8 cm long (vs. 2.5 cm), glabrous sepals (vs. sepals ciliate along the margin), and puberulous, much narrower corolla lobes (vs. corolla lobes adaxially glabrous, relatively wide) and may represent a separate allopatric “oriental” variety. A newly discovered plant represents a certain interest in ornamental cultivation and breeding. Commercial collection of plants in nature for sale may be a serious factor in their extinction in the wild in the coming future.</p> <p> <b>Studied specimen:</b> — Vietnam, Lai Chau Province, submontane evergreen forest at elevation about 1000 m a.s.l., wild collected plant from street market, November 2022, <i>Nguyen Van Canh s.n.,</i> photo and herbarium prepared from cultivated plant, 18 February 2023, <i>Nguyen Van Canh, L. Averyanov, AL 2040</i> (LE 01170321 https://en.herbariumle. ru/?t=occ&id=165964, photos—LE 01123815 https://en.herbariumle.ru/?t=occ&id=165104).</p>Published as part of <i>Nguyen, Van Canh, Averyanov, Leonid V., Nguyen, Quoc Bao, Dang, Van Son, Nguyen, Van Khuong, Maisak, Tatiana V. & Truong, Ba Vuong, 2023, A new species, Hoya honglenae and the first report of H. acuminata and H. phuwuaensis (Apocynaceae, Asclepiadoideae) in the flora of Vietnam, pp. 60-68 in Phytotaxa 632 (1)</i> on pages 61-62, DOI: 10.11646/phytotaxa.632.1.5, <a href="http://zenodo.org/record/10435180">http://zenodo.org/record/10435180</a&gt