Description from Flora of China
Herbs, perennial (?or annual), 1-50 cm, erect or ascending to procumbent or prostrate from creeping and rooting base; stems much branched, branches curved-ascending to spreading or straggling, all or mostly flowering. Stems terete, slender, eglandular. Leaves with petiole 1-7(-10) mm; blade oblong or lanceolate-elliptic to obovate or suborbicular, 0.5-3.5(-5.2) × 0.3-1(-1.7) cm, thickly papery to submembranous, abaxially paler or ± glaucous; laminar gland dots pale, rather large, fairly dense, usually ± prominent, rarely also 1 or 2 black; intramarginal or marginal glands black, ± dense especially distally; main lateral veins 3-paired, tertiary reticulation fine, rather dense; base cuneate to angustate or more rarely rounded to subcordate, apex rounded to rarely obtuse. Inflorescence (1-)5-28-flowered, from 1 or 2 nodes, usually with long (1-)3-7-flowered branches from up to 5 nodes below, the whole narrowly to broadly pyramidal; bracts and bracteoles linear (or lower bracts leaflike), entire or more rarely with scattered black marginal glands, sessile or on short cilia, and sometimes glandular auricles. Flowers 5-8 mm in diam., stellate; buds ellipsoid, apex obtuse. Sepals free, erect in bud, ± spreading in fruit, equal to unequal, very narrowly oblong-lanceolate or rarely narrowly elliptic-oblong to linear, 2.3-3.2(-3.4) × 0.5-0.9 mm; laminar glands pale or rarely black, lines to dots, variable in size and number; marginal or submarginal glands black or reddish, few (sometimes only apical) or absent; margin entire or occasionally sparsely glandular-ciliate (especially toward base), apex acute or rarely subacute; veins 3. Petals ?bright yellow, narrowly oblong, 3-5.5 × 1-1.2 mm, ca. 1.5 × as long as sepals; laminar glands pale, 1 or 2 dots, or absent; marginal glands 1 or 2 near apex and occasionally elsewhere, sessile or immersed; margin entire. Stamens (9-)17-22, apparently 3-fascicled, longest (2.5-)3-5 mm, 0.7-1 × as long as petals. Ovary ± broadly to narrowly ellipsoid; styles 3(or 4), (0.5-)1-2.5 mm, 0.65-1.3 × as long as ovary, outcurving. Capsule broadly ovoid to orbicular, 3.5-4 × ca. 3.5 mm, exceeding sepals. Seeds yellow-brown, 0.5-0.6 mm; testa densely but shallowly reticulate-scalariform. Fl. Jun-Aug(-Oct), fr. Aug-Nov.
Hypericum petiolulatum is closely related to H. seniawinii, of which it appears to be an upland derivative. It has two subspecies: subsp. yunnanense is confined to China and adjacent N Vietnam, whereas subsp. petiolulatum is distributed from Yunnan, Sichuan, and Xizang along the Himalayan range to Nepal.
Hypericum petiolulatum subsp. yunnanense has been confused with smaller-flowered forms of H. seniawinii with narrow and/or cuneate-based leaves, but can be distinguished from them by the shorter styles and smaller, broader capsule and usually by the absence or paucity of marginal sepal glands (not in a continuous row).
Mountain slopes, thickets, grasslands, grassy slopes, stream banks, cliffs, roadsides, forest margins; (300-)800-3100 m. Fujian, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, SE Xizang, Yunnan [Bhutan, NE India, N Myanmar, Nepal, N Vietnam].