Description from Flora of China
Shrubs, 1-1.5 m tall; branches erect to arching. Stems 4-angled and ancipitous when young, eventually terete; internodes 1-3 cm, shorter than leaves. Leaves subsessile; blade narrowly elliptic, 3.5-6.5 × 0.7-2(-2.7) cm, subleathery, abaxially paler to glaucous; laminar glands small dots and short streaks; abaxial glands dense to sparse; main lateral veins 3- or 4-paired, tertiary reticulation rather lax, often conspicuous; base cuneate, apex acute to rounded-apiculate. Inflorescence 1-8-flowered, from 1(or 2) nodes, rounded to flat-topped; bracts deciduous, small, lanceolate to large, leaflike. Pedicels 0.8-2 cm. Flowers 3.5-4.5 cm in diam., shallowly cupped to stellate; buds ovoid, apex acute. Sepals outcurved in bud, reflexed in fruit, narrowly elliptic to ovate or leaflike, unequal, 1-2 cm × 4-10 mm; laminar glands basally lines, toward apex dots, margin entire, apex acute or acuminate. Petals bright yellow, sometimes tinged red, oblanceolate-obovate, 1.7-2 × 0.9-1.1 cm, 1-2 × as long as sepals; margin entire, eglandular; apiculus acute. Stamen fascicles each with 40-60 stamens, longest 1.2-1.5 cm, ca. 0.7 × as long as petals. Ovary ovoid-conic, 6-8 × 4-6 mm; styles 5-6 mm, 0.8-0.9 × as long as ovary, free, suberect, outcurved near apex. Capsule narrowly ovoid-conic, (1.6-)1.8-2.1 × (0.7-)1-1.2 cm, turning purplish red when maturing. Seeds dark reddish brown, 1.1-1.5 mm, with terminal and lateral wing; testa linear-foveolate. Fl. Jul-Oct, fr. Aug-Oct.
Hypericum subsessile is a relict species that occurs in two widely separate localities. Its nearest ancestral relative is in N Thailand (H. siamense N. Robson).
● Thickets and open areas in mixed forest on mountain slopes; 2400-3000 m. C Sichuan (Hanyuan), W Yunnan (Dali).