Herbs, perennial, (0.05-)0.1-0.4 m tall or long, erect or decumbent to prostrate from creeping, rooting and branching base; stems scattered or clustered or often carpeting, often slender, unbranched above or rarely with one pair of ascending branches below inflorescence. Stems terete or 2(-4)-lined, eglandular. Leaves sessile (uppermost or very rarely all) or to 1 mm petiolate, lower smaller, erect to appressed, soon deciduous; blade broadly ovate or circular to broadly oblong or broadly elliptic or obovate-spatulate, 0.4-2.5(-3.5) × 0.2-1.5(-2.5) cm; subpapery to submembranous, abaxially paler or slightly glaucous; laminar gland dots all pale and very small or some or all black, rather dense to sparse or absent; intramarginal glands black and dense or reddish to pale and rather sparse; main lateral veins 3(or 4)-paired, tertiary reticulation dense; base rounded to truncate or subcordate or (lower) cuneate, margin entire, apex rounded or retuse to obtuse. Inflorescence 1-5(-7)-flowered, from 1(or 2) nodes, subumbelliform or bifurcate; bracts leaflike, the pair usually wider than inflorescence, entire; bracteoles narrowly ovate to lanceolate, with black-glandular-ciliate margin and auricles. Flowers (0.6-)1-2.5 cm in diam., stellate or reflexed; buds narrowly ovoid, obtuse. Sepals 5 subequal or 4 in unequal pairs, free, erect, oblong or elliptic to narrowly ovate or linear-lanceolate, 2.5-7 × 1-3 mm; laminar glands all pale or parts or all black, linear; marginal glands black or reddish to pale; margin glandular-ciliate to entire, apex obtuse (rarely acute) to rounded; veins 5-7. Petals 4 or 5, golden yellow, lanceolate-oblong to narrowly ovate, (0.3-)0.5-1.5 cm × 1-4.5 mm, 1-2 × as long as sepals; apical gland reddish, other marginal glands absent; laminar glands pale or black, few, lines to streaks, or absent; margin entire. Stamens 10-45, apparently 3-fascicled, longest 4-9 mm, 0.6-0.8 × as long as petals. Ovary ovoid to subglobose, 2-5 × 1.5-2.5 mm; styles (2 or)3(or 4), 1.5-3 mm, 0.5-1 × as long as ovary, divergent. Capsule broadly ovoid to globose, (5-)6-8 × (3-)4-6 mm, ca. 1.5 × as long as sepals. Seeds yellowish brown, 0.7-0.8 mm; testa shallowly foveolate. Fl. Jun-Aug, fr. Aug-Oct.
Clearings in forests and bamboo forests, thickets, grassy or stony slopes, streamsides, rock crevices; 2900-3900 m. W Sichuan, SE Xizang, Yunnan [Bhutan, NE India, N Myanmar, Nepal].
A detailed study has revealed not only that Ascyrum filicaule is a Hypericum, but that it is only with difficulty separable from H . monanthemum. This species displays a western reduction trend from China to Nepal, while the reduction trend in A. filicaule goes in the reverse direction, from Nepal and NE India (Sikkim) to Yunnan and Myanmar. In Nepal, NE India (Sikkim), and Bhutan there is an area of morphological overlap, where some specimens have perianth states intermediate between 5-mery and 4-mery. It therefore seems appropriate to treat these taxa as subspecies.