About 100 species of low growing, mainly evergreen and woody based perennials mostly from the southern hemisphere but also in the mountains of Central America, Mexico, California and Hawaii. Several species are naturalised in Europe and elsewhere. The genus can be divided into two groups on the way the flowers are arranged; in dense globular heads or interrupted spikes. All the species described have pinnate leaves with two basal stipules and toothed leaflets. In general, the foliage is pleasing, often with a fern-like quality and either bright green or tinted grey-blue, purple or bronze. The largely insignificant flowers are followed by burr-like fruits, the soft or hard and sometimes barbed spines of which can be yellowish, red or warm brown. The red burred species, e.g. A. microphylla, can be quite showy. Flowering and fruiting takes place from summer to early autumn.
Most of the species in cultivation eventually form large mats and are unsuited to the smaller rock garden. They make good ground cover and can be used to form an alpine lawn where space permits. For the most part those not worth growing are coarse, sometimes rampant spreaders without obvious redeeming features. On the other hand, in the wild many form large and highly variable species complexes. The possibility of some really choice variant arising from any of them should never be dismissed out of hand. Attention is drawn equally to vices and virtues here so that certain specific names may be viewed with deepest suspicion by all but the dedicated, uncritical Acaena fanatic! In particular, several species mix very attractive foliar characteristics with pestiferous stick-tight fruiting heads. In such cases it is worth bearing in mind that all their evil reputations are based upon what happens to travellers and farm animals walking unavoidably through extensive tracts of these plants in the wild. Any well drained soil is suitable, either acid or alkaline, and a site in full sun, though some shade is tolerated. Propagation is by seed, cuttings or division in spring or autumn.
a, A. adscendens; b, A. novo-zelandiae; c, A. ovalifolia;