Perennial herbs up to 0.8 m tall, glabrous (except in ‘H. setiferum’; see 8. H. rochelii), sometimes glaucous, with stems erect to procumbent from taproot, branching usually absent below inflorescence, very rarely lateral with one branch below or with branches throughout stem and/or basal, rarely rooting, with dark (black) glands on leaves (only lower ones in 3. H. vesiculosum), sepals, petals and anthers and occasionally on ovary and capsule. Stems terete or narrowly 2-lined or rarely slightly 4-lined, eglandular. Leaves opposite, decussate, sessile, free, persistent, coriaceous to chartaceous; lamina entire or rarely with upper ones glandular-ciliate to -denticulate, with venation pinnate; laminar glands pale and/or black, punctiform; intramarginal glands black; ventral glands absent. Inflorescence 1–c. 70-flowered, with branching wholly monochasial or first branching dichasial, from 1–3(–4) nodes, almost always without subsidiary branches. Flowers stellate, homostylous. Sepals 5, free or connate at the base, imbricate, persistent, erect in fruit, with margin ciliate to fimbriate or very rarely subentire; veins (1–)3–5(–7); laminar glands pale and/or black, punctiform and/or striiform; marginal glands black, regular or rarely absent. Petals 5, persistent, erect but not twisting after flowering, without apiculus; margin entire or ciliate; laminar glands pale and/or black, punctiform; marginal glands black, distal only or sometimes irregular or submarginal below. Stamen fascicles ‘3(4)’, persistent, with stamens totalling c. 30–80; anther gland black; pollen type X. Ovary with 3(4) axile placentae, each ∞-ovulate; styles 3(–4), diverging or spreading-ascending; stigma narrowly capitate. Capsule 3(–4)-valved, coriaceous, with valves with ± interrupted lateral vittae (rarely along with longitudinal pairs of vittae, in 1. perfoliatum) or short swollen vittae or all vesicular, elongated to ovoid, pale to amber or black. Seeds cylindric, not carinate or appendiculate; testa ribbed-foveolate to ribbed-scalariform or ribbed.
BASIC CHROMOSOME NUMBER (X). 8, 7; ploidy 2.
Meadows, among rocks and in montane woodland, often in damp or shaded places; 0–2700 m.
Mediterranean region, western Alps, Carpathians, Balkans, Caucasus, Black Sea areas, and Macaronesia: Austria, Slovenia, Croatia, Romania, Ukraine, Serbia, Montenegro, Bosnia & Herzegovina, Bulgaria, Macedonia, Albania, Greece, Crete, northern and western Turkey, Georgia, southern Russia (Krasnodar), Cyprus, Syria, Lebanon, Italy, southern France, Switzerland, Spain, Portugal, Balearic Islands, Corsica, Sardinia, Tunisia, Algeria, Morocco, Canary Islands, Madeira.