Camellia puhoatensis is morphologically similar to C. chrysanthoides, C. flavida and C. petelotii, but differs in having young puberulous shoots, mature leaves sparsely puberulous abaxially with leaf bases rounded or broadly obtuse, petioles and pedicels puberulous, tepals 12–13 and the ovary and styles pubescent.

Type. VIETNAM. Nghe An Province: Que Phong District, Dong Van Commune, Pu Hoat NR, 19°43'31"N, 105°05'43"E, 270 m elev., 30 December 2018, Do Ngoc Dai, Le Thi Huong, Nguyen Danh Hung, DHH-682 (holotype VNM; isotypes P, DLU).

Figure 1. 

Camellia puhoatensis. A Leaf, adaxial view B venation detail of leaf (abaxial surface) C flower (lateral view) D flower (top view) E bracteoles (inner surfaces shown) F sepals (adaxial surfaces) G petals (adaxial surfaces) H androecium (one part) I stamen J gynoecium (with sepals and petals). Drawn from the holotype by Van-Dung Luong.

Shrub to tree, 2–7 m tall; young shoots puberulous then glabrous when aging, purple towards terminals; semi-mature branches brown, smooth, glabrous, leaf scars prominent; adult branches and trunk light grey, smooth with lighter-coloured patches and covered by lichens; axillary leaf buds rudimentary, roughly triangular, flat, with rounded apex, pubescent, brown, bud scales small but prominent, 1–3 mm long. Leaves: juvenile leaves forming a narrow tube when young, soft, somewhat pendulous, purple in colour; young leaves slightly serrate, shiny, purple, adaxially glabrous, abaxially puberulous; developing leaves descending, narrow, shiny, purple to green-purple tinted, abaxial surface puberulous; mature leaves serrate, irregularly towards the apex, 17–23 × 5.0–6.5 cm; petiole 8–16 × 4–5 mm, puberulous; lamina thin, coriaceous, oblong ovate or oblong, leaf apex acuminate or narrowly acuminate, base rounded or broadly obtuse, adaxially dark green and glabrous, abaxially pale green and sparsely puberulous; primary vein continues as a shallow channel on the adaxial side of the petiole, 2.0–2.5 mm wide proximally, less than 1.0 mm distally, proximally light green and shiny on both sides; secondary venation pinnate, indistinctly brochidodromous, partially eucamptodromous on some leaves, with 10–13 pairs; midribs and lateral veins sunken adaxially; veins distinct proximally, less so towards the apex and the margins; tertiary venation very indistinct, sometimes lacking, more prominent at the leaf margins. Flowers usually solitary, sometimes together in groups of 2 flowers borne on a short bracteate shoot, terminal, rarely axillary, lacking scent, 4.5–6.0 cm in diameter; pedicel stout, covered by purplish-red perulae, 7–10 mm long, puberulous; flower buds unevenly globose in shape, 2.2–2.6 × 2.0–2.3 cm, yellowish-red tinted, open flowers somewhat circular; bracteoles (sensu Sealy 1958) 3–4, opposite, orbicular, 1.5–2.5 × 1.5–3.0 mm, abaxially red to yellow-red tinted, adaxially paler, glabrous, margins ciliate, persistent; sepals 5, persistent, orbicular or subglobose, 0.6–1.5 × 0.8–1.8 cm, abaxially dull red and pubescent, adaxially pale yellowish and glabrous, margins ciliate; petals 12–13, arranged in 3 whorls, bright yellow, sometimes with large red patch on the outer ones; outermost whorl comprising 3 or 4 petals, orbicular to broadly obovate, 2.2–2.8 × 1.6–2.3 cm, abaxially pubescent, adaxially glabrous; middle whorl comprising 4 or 5 petals, broadly obovate, 2.4–3.3 × 1.8–2.5 cm, abaxially pubescent, adaxially glabrous; innermost whorl of 3 or 4 petals, orbicular to broadly obovate, 2.3–2.5 × 1.7–2.2 cm, abaxially pubescent, adaxially glabrous, basally united with outermost filaments 5–7 mm. Androecium numerous stamens, in 4–5 whorls, light yellow, 2.5–2.8 cm long, glabrous; outer filaments basally united for 1.5–1.8 cm forming a cup, inner ones basally united for 3–5 mm, free above union; anthers yellow, 2.2–2.8 × 1–1.5 mm, with two longitudinal striations, dorsifixed. Gynoecium superior, 3–(4)-loculed, ovoid terminating into 3–(4) styles, 2.5–3.0 × 3.0–3.5 mm, slightly longitudinal striations, pubescent, 2 ovules per locule; styles free to the base, 1.8–2.3 cm long, pubescent. Capsule not seen.

Figure 2. 

Camellia puhoatensis. A young shoot B terminal buds C solitary bud and axillary flower (side view) D flower and pollinated flower (side view) E close-up of flower (front view) F immature fruit G a part of branch showing leaves abaxial and opening flower H leaves adaxially I bracteoles J sepals K petals L androecium with stamens M gynoecium (with sepals and styles). Photos by Ngoc-Dai Do, the colour plate prepared by Ngoc-Sam Ly.

Flowering from November to January of the next year.

Camellia puhoatensis is currently found only from the type locality. It grows on moist fertile and sandy soils along mountain streams and hill slopes in evergreen broad-leaved forests in Pu Hoat Nature Reserve, Vietnam, at elevations of 270–450 m.

At present, only a single population of about 300 scattered mature individuals of Camellia puhoatensis was observed in the type locality, with an estimated extent of occurrence (EOO) less than 100 km² and an area of occupancy (AOO) less than 1 km². The population is highly threatened due to loss of habitat within its range and high market demands for wild, yellow-flowered camellias which are intensively collected for sale by local people. Therefore, C. puhoatensis is preliminarily categorised as Critically Endangered [B1ab (i, ii, iii) + 2ab (ii, iii), D], according to the IUCN Categories and Criteria (IUCN 2017).

The specify epithet ‘puhoatensis’ refers to the type locality.

Leaves and flowers were harvested and used for tea by the local people.

Paratypes. Vietnam. Nghe An Province: Que Phong District, Dong Van Commune, Pù Hoạt NR, 19°48'45"N, 105°5'39"E, 320 m elev., 2 September 2018, Đỗ Ngọc Đài, Nguyễn Danh Hùng, Lê Thị Hương, DHH 120 (VNM); the same locality, 19°48'31"N, 105°05'43"E, 280 m elev., 16 January 2019, Đỗ Ngọc Đài, Nguyễn Danh Hùng, Lê Thị Hương, DHH 790 (DLU), DHH 791 (HN).

Vietnamese language: Trà hoa vàng pù hoạt.

The current infrageneric classification of Camellia is derived from three previous publications (Sealy 1958; Chang and Bartholomew 1984; Ming 2000) and was based on the assessment of morphological characteristics. The taxonomic system of Sealy (1958) and Chang and Bartholomew (1984) are used to describe and determine the placement of new taxa within Camellia. These systems are the most detailed and comprehensive study of the genus and also provide the basis for our current understanding of the genus. The taxonomic system of Ming (sensu Ming and Bartholomew 2007) was used for supplementary data only as it appears to be superficially similar to the system of Sealy (Orel and Wilson 2010a). In this paper, we have followed the Sealy’s (1958) taxonomic system to consider the placement of the new species within Section Archecamellia Sealy of Camellia. Morphologically, C. puhoatensis possesses a solitary or paired flowers at terminal (sometimes axillary), stout, thick and erected pedicel, 3–4 persistent bracteoles, 5 persistent sepals (undifferentiated bracteoles and sepals), large yellow flowers with 12 tepals that are inner ones basally connate and adnate to androecium, androecium free above the union with the petals or unified for some distance to form a fleshy cup, filaments glabrous, gynoecium 3(–4)-loculi, styles 3(–4) and free to the base. These characteristics are not only identical to the species of sect.Archaecamellia Sealy (sensu Sealy 1958; sensu Chang and Bartholomew 1984), but also share with species of sect.Stereocarpus which possesses 2 or 4 bracteoles (sensu Sealy 1958), terminal flowers (sensu Chang and Bartholomew 1984), stamens in 3–4 whorls, ovary with 3–5 locules (sensu Ming 2000), as well as sharing with species of sect.Chrysantha Chang, such as distinct peduncle, small floral bracteolates, yellow flowers, three carpels of gynoecium and separate styles (sensu Chang 1979). As characterized by Sealy (1958), sect. Archaecamellia shares several traits with sect. Stereocarpus. These include a solitary and erected flower at the end of the branches, persistent bracteoles and sepals, stamens united with the petals and glabrous filaments. However, traits that are distinctive to sect. Archaecamellia include (6–)11–16 indistinct bracteoles and sepals, 8–14 petals, glabrous or pubescent gynoecium and 3 or 5 free styles (vs. 2 or 4 bracteoles and 5 or 6 sepals, ca. 12 petals, glabrous gynoecium and a single style in sect. Stereocarpus). The sect. Chrysantha also shares several traits with sect. Archaecamellia in having yellow and pedicellate flowers, persistent bracteoles and sepals, glabrous or hairy filaments and gynoecium, but it can be distinguished from sect. Archaecamellia by the axillary flowers, distinct bracts and sepals and 3–5 cleft styles (Chang 1979). Section Archaecamellia is currently comprised of 19 species (Sealy 1958; Ming 2000; Orel and Wilson 2012a; Do et al. 2019a). The new species is most similar to C. chrysanthoides H.T.Chang, C. flavida H.T.Chang and C. petelotii (Merr.) Sealy in having the same plant habit, somewhat oblong leaves, yellow flowers, glabrous 3-loculed gynoecium with 3 styles free to the base. A detailed morphological comparison between C. puhoatensis and these three species is provided in the above diagnosis and in Table 1. Moreover, C. puhoatensis also resembles C. dormoyana (Pierre) Sealy of sect. Stereocarpus (Sealy 1958) and C. velutina V.T. Pham et al. of sect. Chrysantha (Pham et al. 2019) by somewhat oblong leaves, yellow flowers and glabrous stamens. However, Camellia dormoyana is easily distinguished from C. puhoatensis by having the young shoots, mature leaves and petioles all glabrous, the sessile pedicel and 5–6 bracteoles abaxially velutinous, the abaxial petals silky velutinous, the ovary being glabrous and with five locules and the styles united for their entire length and glabrous. Similarly, C. velutina is readily distinguished from C. puhoatensis by its glabrous young shoots, mature leaves and petioles, sepals that are silky velutinous abaxially and velutinous adaxially, the 10 (occasionally 11) petals that are silky velutinous and glabrous ovary and style (see Table 1).