China. Jiangxi Province, Yichun County, Hongjiang Township, Dongnan Village, under bamboo forests, beside the river ditch, 328 m elevation, 8 May 2019, Z.Y. Xiao & X.C.Li, CSFI076074 (holotype: CSFI; isotypes: NF).

Sepal lobes and bractlets, completely glabrous. Most similar to Vicia taipaica, but differs from it by its hastate or lanceolate stipules and subulate bractlets (stipules semi-ovate or lanceolate and bractlets absent in Vicia taipaica). Similar to Vicia dichroantha as well, but differs from it by the light yellow or dull orange colour of the corolla and subulate bractlet (yellow, dark yellow or dull orange corolla, marked purple at apex of standard and braclets, absent in Vicia dichroantha). The new species is restricted to western Jiangxi Province (Figs 1, 2, Table 1).

Figure 1. 

Distribution map of Vicia mingyueshanensis (blue dots) and its closest similar species Vicia taipaica (red dots) and Vicia dichroantha (yellow dots).

Perennial herb, strongly climbing, 0.5–1.8 m tall, glabrous throughout. Root robust, woody, branched, well-developed in depth. Stems flexuous, subquadrangular, striate, branched. Leaves paripinnate, 8–15 cm (excluding the tendril), with 4–6 pairs alternate leaflets, provided with a terminal twining tendril, 2–3 branched; leaflets elliptic to ovate-oblong, margin entire, not toothed, papery, 2.3–3.8 cm long, 0.7–1.5 cm wide, broadly cuneate or suborbicular at the base, mucronulate at the apex, subsessile or shortly petiolulate (to ca. 1 mm long), lateral veins 7–12 paired. Stipules opposite, unequal, margin entire, hastate or lanceolate, 0.4–0.7 × 0.2–0.3 cm. Racemes 10–20 flowered, shorter or nearly as long as the subtending leaves, with peduncle up to 4–8 cm long. Flowers slightly pendent, 1.6–2.0 cm long, bractlet, subulate, 0.2–0.3 × 0.1 cm. Calyx membranaceous, obliquely campanulate, 0.4–0.5 cm long, tubular, gibbous at the base, zygomorphic, with 5 lateral teeth acute, some calyces are cleft. Corolla light yellow or dull orange, standard with 1.3–1.4 × 0.4–0.5 cm, subequalling to wings and keels, apex retuse. Staminal tube 1.2–1.4 cm long, vexillary staminal filament free, anther greenish-yellow. Ovary 0.5–0.6 cm long, with 4–6 ovules. Style geniculate at the base, cylindrical, 0.3 cm long, evenly hairy under the stigma. Pod stipitate, falcate, often apiculate, smooth, 3.0–3.5 × 0.3 cm. Seeds 4–6, oblate-spheroid, brown-green, 0.3–0.4 × 0.3 cm, hilum circumlinear, up to the middle of the circumference long.

Figure 2. 

Vicia mingyueshanensis A, B habitat C habit D the whole plant E pods F pods and seeds G root H inflorescences I leaflets and stipules J bractlet K calyx L tendrils.

Flowering time from May to early June; fruiting in July and defoliation from late July to early August.

The species epithet is derived from the name of the mountain range (Mingyueshan) where the species had been discovered.

The Chinese name ‘明月山野豌豆’ (Ming Yue Shan Ye Wan Dou)

Vicia mingyueshanensis is only known in western Jiangxi Province, Yichun County, Hongjiang Town, Dongnan Village, Mingyue Mountain Region, located in an open area of Phyllostachys edulis J. Houzeau forests with Castanopsis tibetana Hance and Lithocarpus litseifolius (Hance) Chun as associated tree species. The observed population is very small, with fewer than 200 plants growing along roadsides and ditches, accompanied by Oreocnide frutescens (Thunb.) Miq. and Rubus tephrodes Hance. Elevation is 300–650 m above sea level.

Vicia mingyueshanensis is currently only known from a small population in a habitat that is subject to logging and disturbance, thus, it is very rare and distributed in a few patches. On the basis of our field observations, this species is represented by no more than 200 large and mature individuals, along a road where bamboo was being cut. Due to its rarity and a low number of individuals, Vicia mingyueshanensis is considered to be Critically Endangered (CR, B1), according to the IUCN (2019).