Perennial herb 0.2-0.6 m tall, erect or ascending from creeping and rooting base, with stems numerous to few, initially unbranched below inflorescence, later branched above for c. 2/3 of their length. Stems 4-lined, the subsidiary ones (decurrent between leaves) often less prominent or even partially absent, usually with black glands on the lines; internodes 10-50 mm, shorter than to exceeding leaves. Leaves sessile; lamina 15-40 ´ 10-20 mm, broadly to narrowly elliptic, paler beneath, chartaceous; apex rounded, margin plane, base rounded; venation: 3(2) pairs of main laterals from lower quarter to base of midrib, tertiary reticulation dense; laminar glands absent or rarely pale, scattered, sometimes also black, few, punctiform; intramarginal glands black, ± close, irregular in size. Inflorescence (2-)3-c. 15-flowered, from 1-3 nodes, with flowering branches narrowly or curved ascending from up to 5 nodes, the whole cylindric to broadly pyramidal or subcorymbiform; pedicels 1.5-4 mm; bracts and bracteoles up to 5 mm long, narrowly triangular-ovate to narrowly elliptic, entire. Flowers (15-)20-25(-30) mm in diam., stellate to reflexed; buds broadly ellipsoid, rounded to obtuse. Sepals 5, ± unequal, 3.5-4.5(-5) ´ 2-2.7(-3) mm, broadly elliptic to broadly ovate or ± broadly oblong, rounded to obtuse or subacuminate (varying in same flower), entire, erect to recurved in bud, recurved in fruit; veins 5(-7), not or slightly branched; laminar glands pale and sometimes also black, punctiform and sometimes striiform; intramarginal glands pale or occasionally black or often absent. Petals 5, golden yellow, not tinged red in bud, (8-)10-15 ´ 4-7.5 mm, c. 3 ´ sepals, broadly elliptic to obovate or more rarely symmetrically oblanceolate, distally crenate or entire; laminar glands pale and/or black, punctiform and sometimes proximally striiform to linear (in var. immaculatum almost all linear); intramarginal glands few, distal or usually absent. Stamens 50-80(-100), '3'-fascicled, longest 7-10 mm, c. 0.65-0.9 ´ petals; anther gland black. Ovary 3-locular, 2-4 ´ 1.5-2.5 mm, ± broadly ovoid to ovoid-ellipsoid; styles 3, free, 3-4 mm, 1-1.5(-2) ´ ovary, rather narrowly spreadng; stigmas narrowly capitate. Capsule 6-10 ´ 4-6 mm, c. 2-2.5 ´ sepals, ovoid-ellipsoid to ± broadly ovoid; valves with longitudinal vittae, linear to striiform. Seeds dark brown, 0.8-1.2 mm, cylindric, not carinate or appendiculate; testa finely linear-foveolate.
Partial or complete absence of subsidiary lines may possibly indicate hybridisation with H. perforatum (cf. H. ´ desetangsii, p. ).