Description:

• Evergreen perennial herbs or undershrubs, decumbent or spreading, with taproot; bark on old branches reddish brown, thin and exfoliating
• Leaves alternate or sometimes all radical, imparipinnate with leaflets incised or serrate; stipules connate and adnate to base of petiole
• Inflorescences lateral or terminal racemes, heads or interrupted spikes
• Flowers bisexual, bracteate
• Calyx: tube ± obconic, narrowed at apex, usually armed with straight or hooked, few to many spines, sometimes villous; lobes 3-7, valvate, persistent or deciduous
• Petals 0
• Stamens (1)2-4(-10), inserted in throat of calyx tube; anthers dorsifixed, didymous
• Disc lining calyx tube almost closing calyx tube mouth
• Gynoecium of 1 or 2 free carpels; ovules solitary in each carpel, pendulous; styles subterminal, short; stigmas dilated, peltate, fimbriate or penicillate
• Fruit of 1 or 2 coriaceous achenes firmly enclosed in hollow hardened receptacle, which is almost closed at summit and furnished with prickles or awns barbed with reflexed hairs
• Seeds ovoid; testa thin
• x = 7 (aneuploids, polyploidy)

Nomenclature:

• Acaena L.
  • Linnaeus: 145 (1771)
  • Jussieu: 336 (1789)
  • Kunth: 231 (1823)
  • Candolle: 592 (1825)
  • Endlicher: 1244 (1840)
  • Harvey: 290 (1862)
  • Hooker: 623 (1865)
  • Focke: 46 (1894)
  • Bitter: 489 (1912)
  • Romoleroux: 62 (1996)

Distribution & Notes:

• Global: Species ± 100, mainly in cold areas of the southern hemisphere, South America, Atlantic Ocean islands, Australia and New Zealand; a few species are reaching as far north as California and Hawaii; many naturalised elsewhere
• Southern Africa: Species 1: Acaena latebrosa Aiton, Western Cape