Acaena magellanica is aperennial, mat-forming plant with creeping stems, up to 14 cm (6 in) high. The leaves are oblong to linear-lanceolate, with 5 to 10 pairs of ovateleaflets. The flower heads are globular and grow on wiry stems well clear of thefoliage. They are followed by brown, prickly seed heads; the seeds have small hooks which enables them to adhere to clothing, feathers or fur.[2]
In South Georgia,Acaena magellanica may cover the ground in dense patches. It is deciduous, and when the leaves are shed, mosses likeTortula robusta, which grows underneath, flourish.[3]
TheKerguelen Islands are in theSouthern Indian Ocean Islands tundra ecoregion which is characterised by tussock grasses, lichens and liverworts.A. magellanica is one of the few lowforbs that grew here, but the introduction of theEuropean rabbit (Oryctolagus cuniculus), which selectively grazes the species it prefers, eliminated many of the native forbs.[4] When the rabbit was eradicated,A. magellanica and other forbs failed to recover because years of herbivory had depleted their seed banks, and introduced species such asannual meadow grass (Poa annua),mouse-ear chickweed (Cerastium fontanum) anddandelion (Taraxacum officinale) out-competed them.[4]
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