Description: Perennial herbs or subshrubs, often with an unpleasant smell when fresh or crushed.
Leaves opposite; stipules sheathing with 1 or 2 teeth per side.
Inflorescence consisting of 2 to several flowers ± fused at their base, together with their surrounding bracts forming a globose, compound head, usually in forks of stem or terminal; peduncle erect or recurved. Flowers mostly bisexual, or if unisexual then plants dioecious. Calyx 3–5-lobed, persistent in fruit. Corolla 3–5-lobed. Stamens 4, inserted at base of corolla tube; anthers exserted. Ovary 1- or 2-locular, with 1 ovule in each loculus; style filiform, mostly 2-fid.
Fruit a compound capsule dehiscing by the abscission of the apical lid of each flower or several lids are ± fused and shed as a single unit.
Distribution and occurrence: World: c. 15 species, endemic Australia. Australia: mainly temperate regions; Qld, Vic., Tas., S.A., W.A.
Text by T. A. James & W. K. Allen
Taxon concept:
| | Key to the species | |
| 1 | Plants densely to sparsely hirsute or scabrous with hairs to 1 mm long; inner face of seeds without longitudinal ridges | Opercularia hispida |
| Plants glabrous or scabrous with hairs to 0.5 mm long; inner face of seeds with longitudinal ridges (except in Opercularia diphylla) | 2 |
| 2 | Leaves ovate to lanceolate, 5–20 mm wide; calyx-lobes 2–4 mm long | Opercularia aspera |
| Leaves mostly linear to lanceolate or narrow-ovate, 1–8 mm wide; calyx-lobes to 1 mm long
Back to 1 | 3 |
| 3 | Small weak or decumbent herbs; leaves mostly to 3 cm long; seeds pitted without 2 longitudinal ridges | Opercularia diphylla |
| Erect to spreading subshrubs; leaves mostly to 1.5 cm long; seeds transversely wrinkled with 2 prominent longitudinal ridges on inner surface
Back to 2 | 4 |
| 4 | Plants dioecious; branches more or less rigid, terete, 1–2 mm wide; flower heads more or less sessile on little-branched stems; an uncommon species of southern inland N.S.W | Opercularia turpis |
| Plants monoecious; branches lax, more or less angular, to 1 mm wide; flower heads with a peduncle 2–7 mm long and with dichotomous branching at the same nodes on lower part of plant; a widespread species of the coast and tablelands
Back to 3 | Opercularia varia |
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