Description from Flora of China
Hypericum erectum f. angustifolium (Y. Kimura) Y. Kimura; Hypericum erectum var. angustifolium Y. Kimura; H. erectum subsp. longisepalum L. H. Wu & D. P. Yang; H. taisanense Hayata.
Herbs, perennial, 30-70 cm tall, erect or ascending from branching and rooting base; stems solitary or few, unbranched below inflorescence or sometimes branched above. Stems terete, eglandular. Leaves sessile; blade narrowly triangular-ovate to narrowly elliptic, 1.5-5 × 0.8-1.3 cm; thickly papery, abaxially paler; laminar glands black [and sometimes pale], ± numerous, small; intramarginal glands black, dense; main lateral veins 3- or 4-paired, tertiary reticulation rather dense; base cordate-amplexicaul, margin entire, plane or incurved, apex obtuse to rounded. Inflorescence (1 or)3- to many-flowered, from 1-3 nodes, often with flowering branches from up to 6 nodes below, the whole flat-topped to cylindric; bracts and bracteoles reduced leaflike, margin entire. Flowers ca. 1.5 cm in diam., substellate; buds narrowly ellipsoid, apex acute. Sepals free, erect, ovate-lanceolate [to oblong-elliptic], subequal to unequal, ca. 2.5[-7] × 1[-3] mm; laminar glands black, streaks and dots; intramarginal glands black, [rather dense to] sparse or absent; margin entire [to irregularly glandular-ciliate], apex obtuse to acute; veins 5. Petals bright yellow, obovate to oblong, [6-]7-9[-10] × [2-]2.5 mm, 2.5-3 × as long as sepals; laminar glands black, streaks, distal; marginal glands black, inframarginal to prominent, irregular; margin entire [or with scattered prominent glands]. Stamens 25-30[-40], apparently 3-fascicled, longest 5-7 [6-7] mm, ca. 0.7 × as long as petals. Ovary ovoid; styles 3, 2.5-3 mm, 0.8-1[-1.2] × as long as ovary, widely spreading. Capsule ovoid, ca. 1 cm × 4 [5-11 × 3.5-6] mm, [1.2-]2-2.5 × as long as sepals. Seeds yellow-brown, 0.7-1 mm; testa finely reticulate. Fl. Jul-Aug, fr. Aug-Sep. 2n = 16.
In China, Hypericum erectum can always be recognized by the sessile leaves with black gland dots only. The described variation of H. erectum subsp. longisepalum falls within that of this very variable species as a whole; and it was not possible for us to see the diagnostic characters in a color image of a living specimen. This subspecies has therefore been tentatively included in the synonymy of H. erectum.
Grassy slopes; 400-2300 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Sichuan, Taiwan, Zhejiang [Japan (including Ryukyu Islands), Korea (Cheju-do), Russia (Sakhalin)].