This new species is similar to O. flavida in the orange colour of the corolla, but differs from the latter by its much larger corolla (3.3–3.6 cm long vs. 1.5–1.7 cm), the shape of the corolla tube (infundibuliform vs. campanulate) and the reniform anthers which are coherent in two pairs (vs. horseshoe-shaped and not coherent). The two species further differ by the narrowly oblong or elliptic leaf blades in the new taxon (vs. ovate-elliptic to broadly ovate), cuneate leaf base (vs. cordate to rounded), the glandular villous indumentum on the outer surface of the calyx lobes (vs. eglandular villous).

VIETNAM. Lao Cai, Sa Pa distr., Ta Phin cave, in secondary forests, on cliffs nearby waterfalls, 22°20'43.66"N, 103°46'30.48"E, 2017 m elevation, 30 October 2012, type specimen from a plant cultivated in an experimental greenhouse at Kunming Botanic Garden, 7 September 2013, Y.M. Shui et al. B2013-550 (holotype, KUN!; isotype: Herbarium of the Centre for Plant Conservation, Vietnam Union of Science and Technology Associations, Hanoi!).

Perennial herbs. Leaves in basal rosette. Petiole 2.2–2.6 cm long, with dense white glandular hairs; leaf blade coriaceous, narrowly oblong or elliptic, 4–6 × 1.8–3.5 cm, adaxially and abaxially covered by white glandular hairs, more densely on veins, base narrowly cuneate, apex acute, margin crenate; lateral veins 4–5 on each side of the midrib, adaxially depressed, abaxially prominent. Inflorescences axillary, 1–4-flowered. Peduncles 6–12 cm long, with white glandular hairs; bracts 2, lanceolate, 5.6–6 × 1.1–1.2 mm, abaxially covered by white glandular hairs. Pedicel 1.5–1.8 cm long. Calyx 5-lobed from base, lobes equal, linear-lanceolate, 7–8 × 1.1–1.2 mm, entire, adaxially glabrous, abaxially with white glandular hairs. Corolla deep orange, slightly bilabiate, 3.3–3.6 cm long, inside pubescent, outside with white glandular short hairs; tube infundibuliform, 2–2.2 cm long, 2.7–3 mm in diam. at base and 8–9 mm in diam. at throat; adaxial lip 2-lobed, lobes suborbicular, 8.5–9 × 11–12 mm, apex obtuse; abaxial lip 3-lobed, lobes suborbicular, slightly equal, 13–14 × 8–9 mm, apex more or less rounded. Stamens 4, anthers coherent in two pairs, filaments adnate to base of corolla tube, adaxial stamens 2–2.2 cm long, abaxial stamens 2.6–2.8 cm long; filaments with white glandular hairs; anthers reniform, basifixed; staminode 1, adnate to base of corolla tube, 5–6 mm long. Pistil 3.1–3.5 cm long when mature; ovary cylindrical, 2–2.2 cm long, glabrous; style 1–1.3 cm long, with white glandular hairs; stigma 1, flattened with central depression. Disc ringlike, yellowish, 2–3 mm high. Capsule straight, cylindrical, 2.1–2.5 cm long.

This new species is endemic to Sa Pa, northern Vietnam and grows densely on cliffs by waterfalls along deep valleys in evergreen broad-leaved forests, at an elevation of around 1800–2010 m. Flowering from August to October and fruiting from September to October.

The species epithet refers to the large size of the flowers. Based on the authors’ observation and other relevant publications (Wang et al. 1990, 1998), the new species has one of the largest flowers in Oreocharis.

This new species appears to be restricted to a very moist habitat in Sa Pa, Lao Cai Province, northern Vietnam. It grows on several steep cliffs at 1800–2100 m elevation by waterfalls with flowing water throughout the year (Fig. 1A). It flowers during the rainy season (September to October), during which the locality is inaccessible. This is likely the reason why it had not previously been discovered. It is naturally protected by its inaccessible habitat on the cliffs. According to our observations in the field, the two known populations harbour about 100 mature individuals in each. In fact, there are many waterfalls at this altitudinal range and, thus, the real number of populations and individuals may be higher. Nevertheless, its unusually humid habitat might be affected by climate change-induced droughts. Overall however, the species has been classified as “Data Deficient” [DD] following IUCN Red List Categories and Criteria (IUCN 2012).

Figure 1. 

Oreocharis grandiflora W.H.Chen, Q.H.Nguyen & Y.M.Shui, sp. nov. (A–F) and O. flavida Merr. (G–I) A Habitat (red arrows indicate position of plants in the field) B Mature plant C Abaxial leaf surface D Front view of flower E Lateral view of flower F Opened corolla, pistil, disc and calyx G Plant H Inflorescence and open flowers I Dissected flower, showing corolla with free anthers, pistil, disc and calyx. Scale bars: A, C–F = 1 cm; B,G = 2 cm; H, I = 5 mm. All photographs by Yu-Min Shui.

VIETNAM. Lao Cai, Sa Pa distr., Ta Phin cave, in secondary forests, 22°20'43.66"N, 103°46'30.48"E, 2017 m elevation, 30 October 2012, in fruit, Q.H.Nguyen, T.H.Nguyen, Y. M. Shui, Y. K. Sima, S. X. Yang, Z. Zhou, J. Liu CK687 (KUN!, Herbarium of the Centre for Plant Conservation, Vietnam Union of Science and Technology Associations, Hanoi!).

This new species resembles Oreocharis flavida, but differs in the characters in Table 1 (see also Fig. 1). Additionally, the corolla size range is larger than any other species in the former delimitation of Oreocharis. In size and shape, the corolla of the new species resembles that of Oreocharis ronganensis (K.Y. Pan) Mich. Möller & A. Weber (formerly Ancylostemon ronganensis K.Y. Pan), but in the latter the corolla is pink, not deep orange. This is a rare colour in Oreochariss.l., since only about six of the >106 species have a corolla of such an intensely deep orange colour.

This new species is similar to O. hirsuta Barnett from Thailand, but differs from it in its pubescent petioles (vs. hirsute), (sub)orbicular leaves (vs. narrowly ovate or lanceolate), rounded leaf apex (vs. acute to short acuminate), crenate leaf margin (vs. bi-serrate), narrowly infundibuliform corolla tube (vs. tubular), anthers coherent in pairs (vs. free) and glabrous filaments (vs. hirsute).

VIETNAM. Lao Cai, Sa Pa distr., Ta Phin cave, in secondary forests, 22°20'54.48"N, 103°46'12.98"E, 1879 m elevation, 30 October 2012, type specimens from plants cultivated in an experimental greenhouse at Kunming Botanic Garden, 7 September, 2013, Y.M. Shui et al. B2013-551 (holotype, KUN!; isotype, Herbarium of the Centre for Plant Conservation, Vietnam Union of Science and Technology Associations, Hanoi!).

Perennial herb. Leaves in basal rosette. Petiole 4–7 cm long, densely long pubescent; leaf blade (sub)orbicular, 3–9 × 2.4–8.9 cm, adaxially sparsely hirsute, abaxially pubescent, more densely so on venation, base cordate, apex rounded, margin crenate; lateral veins 5–6 pairs, adaxially depressed, abaxially prominent. Inflorescences axillary, 1–2-flowered. Peduncles 8–11 cm long, densely white villous; bracts 2, linear-lanceolate, 5–22 × 0.7–1.2 mm, adaxially subglabrous, abaxially pubescent; pedicel 1.8–2 cm, pubescent. Calyx 5-parted almost from base, segments linear-lanceolate, 8–15 × 1–4 mm, margin dentate, adaxially glabrous, abaxially white hispid. Corolla yellow, bilabiate, 3–3.5 cm long, inside pubescent, outside white glandular; tube narrowly infundibuliform, 2–2.5 cm long, 3–3.5 mm in diam. at base and 6–7 mm in diam. at throat; adaxial lip 6.5–7 mm long, 2-lobed, lobes suborbicular, 3.3–3.5 × 3.5–3.8 mm, apex obtuse; abaxial lip 3-lobed, lobes sub-oblong, almost equal, 8–10 × 6–8 mm, apex obtuse. Stamens 4, anthers coherent in two pairs, adaxial stamens 5–7 mm long, adnate to corolla tube 1.2–1.5 mm from base, abaxial stamens 7.5–8 mm long, adnate to corolla tube 1–1.2 mm from base; filaments glabrous; anthers round, basifixed, dehiscing longitudinally; staminode 1, 2.5–3 mm long, adnate to corolla tube 6–7 mm from base. Pistil 1.7–2.1 cm long when mature; ovary cylindrical, 1.2–1.4 cm long, glabrous, 2-locular; style 5–7 mm long, white pubescent; stigma 1, flattened with a central depression. Disc cylindrical, yellowish, 2.8–3 mm high, margin shallowly dentate. Capsule straight, cylindrical, 3–5 cm long. Seeds oblong, 1.1–1.2 mm long.

This new species is also endemic to Sa Pa, northern Vietnam and grows widely scattered on wet ground along road sides or along streams in evergreen broad-leaved forests, at an elevation of 1700–1890 m. Flowering from August to September and fruiting from September to October.

The species epithet refers to the unusually long length of the corolla tube in Oreocharis.

Endangered EN B2ab (iii), following IUCN (2012) guidelines. This is based on an EOO of < 35 km², being known from fewer than five populations and with disturbed locality.

VIETNAM. Lao Cai, Sa Pa distr., Kuoang Village, 22°28'43.66"N, 103°47'41.5"E, 1700 m elevation, growing on humus soil in wet and shady places, 11 September 2005, X. P. Vu, D. H. Duong, V. D. Nguyen, Q. B. Nguyen, T.D.Nguyen, R. de Kok, G. Bramley, G. Challen, M. Vorontsova HNK 58 (K!); Sa Pa, Ta Phin cave, in secondary forests, 22°20'54.48"N, 103°46'12.98"E, 1879 m elevation, 30 October 2012, in fruit, Q. H. Nguyen, T.H. Nguyen, Y. M. Shui, Y. K. Sima, S. X. Yang, Z. Zhou, J. Liu CK670 (KUN!, Herbarium of the Centre for Plant Conservation, Vietnam Union of Science and Technology Associations, Hanoi!); Sapa distr., the path to Fanxipan from Ton Station, 22°20'01"E, 103°46'47.8"E, 2000 m elevation, 10 August 2007, in fruit, N. V. Du, P. Wharton & B. Wynn-Jones 10 (K!); Tonkin, route de Chapa à la garderie du Col de Lo Qui Ho, 1800 m elevation, September 1929, in flower, P. A. Pételot 5177 (P: P03934211!; P04079324!; P03511246!); Col de Lo Qui Ho, elev. 2000 m, August 1933, in flower, P. A. Pételot 7247 (P: P03934227); Col de Lo Qui Ho, elev. 1900, 16 August 1926, in flower, Poilane 12965 (P: P04079331).

A previous collection of this species, X.P. Vu et al. HNK 58, K!, had been identified as Oreocharis hirsuta, a species from Thailand that demarcates the southernmost distribution of the genus (Barnett 1961; Möller et al. 2011). When comparing the specimens studied here with type material and recent collections of O. hirsuta in the herbaria of the Royal Botanic Gardens, Kew (K) and the Royal Botanic Garden Edinburgh (E), it was found that they can be morphologically differentiated (Table 2; Figs 2I–L). Earlier collections by Pételot and Poilane in Vietnam and deposited in the Muséum National d’Histoire Naturelle in Paris (P), remained unnamed until now. These collections were made near Chapa at Lo Qui Ho, a station on the slopes near the summit of Fan Si Pan).

Figure 2. 

Oreocharis longituba W.H.Chen, Q.H.Nguyen & Y.M.Shui, sp. nov. (A–H) and its most similar species, Oreocharis hirsuta Barnett (I–L) A Habitat B Mature plant C Abaxial leaf surface D, E Front view of flower F Pistil with immature stigma, disc and calyx G Lateral view of flower H Opened corolla I Mature plant J Flower and fruits K Front view of flowers L Side view of flowers. Scale bars: A, I =5 cm, D–H = 1 cm; J, K, L= 2 cm. A–H photographs by Yu-Min Shui, I–L by Preecha Karaket of Middleton et al. 4550.

Figure 3. 

Oreocharis grandiflora W.H.Chen, Q.H.Nguyen & Y.M.Shui, sp. nov. (all drawings based on the holotype Y.M. Shui et al. B2013-550 in KUN, drawn by Y.F. Shui) A Habit B Opened corolla showing corolla lobes and two pairs of stamens C pistil at stigma receptivity and calyx.

Figure 4. 

Oreocharis longituba W.H.Chen, Q.H.Nguyen & Y.M.Shui, sp. nov. (all drawings based on the holotype Y.M. Shui et al. B2013-551 in KUN, drawn by J.X. Liu). A Habit B Abaxial leaf surface C Opening flower from below showing the inflated part near the distal end of the corolla tube D Open flower from above E Opened corolla showing two pairs of stamens F Pistil (immature at male stage), disc and calyx G Front view of flower.

With its long corolla tube up to 2.5 cm, O. longituba has the longest tube amongst the yellow flowered species with infundibuliform corollas in Oreocharis. It is also the only species with coherent anthers amongst species in the previous, narrower concept of Oreocharis. In the current wider delimitation of Oreocharis, the corolla tube is more similar in shape, though not in size, to those species previously placed in Ancylostemon Craib and Paraisometrum Wang (Wang et al. 1990, 1998; Weitzman et al. 1997; Chen et al. 2014).