Bracken means ‘fern’ in old northern European language and applies to a worldwide group of closely related species. Ours (rārahu) is Pteridium esculentum and is found in West Polynesia and Australasia.
It was uncommon in pre-human New Zealand, but became extremely widespread following Māori burning of lowland forest from the early 13th century, and was maintained by fire.
In wet areas, bracken decays quickly and forest species establish, but in dry areas it persists for a long time. It builds a good peaty soil because it produces deep litter, accumulates soil minerals and attracts soil fungi. Bracken protects soil from erosion and increases the warmth and moisture and suppresses exotic weeds.
In good soil the underground stems contain 10–30% starch. It was the preferred food for travellers, being light in weight and easily stored for months. Before flour was available it was the main carbohydrate in the diet.
Fernland older than about 3 years was burnt in late winter and rhizomes (aruhe) dug in November. Thick crisp rhizomes were selected, then air dried. Before eating they were roasted lightly, then beaten with a wooden mallet (patu aruhe), before being sucked individually or soaked in liquid such as the juice of tutu.