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This article was first published in the Tararua Tramper Volume 96, # 10, November 2024

November in the hills with Michele Dickson, Chris Horne

Pteridium esculentum, rārauhe, bracken, bracken fern

bracken.jpg: 509x486, 229k (2024 Oct 28 22:35)
Pteridium esculentum, rārauhe, bracken, bracken fern
Photo: Jeremy Rolfe

For general comments about ferns, see Asplenium oblongifolium in the October 2015 Tramper, and a description of the life cycle of ferns in Asplenium bulbiferum in the December 2015 Tramper. Pteridium esculentum is one of several similar-looking ferns within the large fern family - the Dennstaedtiaceae family - but the only species in the genus Pteridium in New Zealand.

Origin of the botanical name

Pteridium is derived from the Greek word 'pteridos' meaning ‘fern’; esculentum is derived from the Latin word 'esculentos' Distribution Rārauhe / bracken is found in Tasmania, Australia, many Pacific islands and South East Asia. It is native to New Zealand where it occurs on Kermadec Islands, Manawatāwhi / Three Kings Islands, Te Ika a Māui / North Island, Te Waipounamu / South Island, Rakiura / Stewart Island, Rekohu / Chatham Island and our subantarctic islands.

Growth habit and reproduction

The very narrow pinnules / frond parts of rārauhe / bracken and general familiar appearance make it very distinctive. The fronds develop from deep, creeping underground rhizomes. The stalks of bracken are red-brown or orange-brown, rough near tips but becoming smooth and woody, almost hairless, stiff and reaching heights of up to 4 m. The fronds are dark green, lighter underneath, 0.25–1.5–1.8 × 0.2–1.0–1.4 m wide, and 3–4-pinnate with midribs narrowly winged. Fronds sometimes brown off in winter. Sori / sacs which contain spores – the equivalent of seeds produced by flowering plants – form a continuous line along the underside edges of the frond segments. When ripe, the sori are spread by the wind. Rārauhe / bracken is the most invasive fern species in New Zealand, particularly in many hill-country pastures and causes problems in forestry. However, it also acts as a nursery plant for other native seedlings in other reverting bush situations and in time disappears under regenerating forest.

Uses

Firstly, a mention of toxicity: the rhizomes are poisonous and the young bracken fronds have been found to be highly carcinogenic – don't try eating any part of the plant would be best. However, for Māori the rhizomes were a staple food produced by specific harvesting, storage, preparation and cooking procedures. Medicinal uses included bracken as an antidote for sea-sickness and plant pieces being worn on parts of the body to protect or cure the wearer from various ailments. In fishing and hunting, branches were used to catch freshwater crayfish. In construction, fronds were used to line floors of storage pits and stalks used for lining large public whare/huts. For pastime uses, straight stems were used for spears or darts in games with the ends being bound with flax; stems were also used in kite making. In traditions and proverbs, rārauhe / bracken is well represented.

Where to find rārauhe / bracken?

It is common everywhere from lowland to subalpine areas, on forest margins and clearings, roadsides, shrubland, in open sites and on farmland where it may form bracken fern-land. You can see rārauhe / bracken in open moist places in the Tararua, Remutaka and Aorangi ranges and in Wellington area reserves.

Category
Botany 2024

In The Hills 2024-10 < Index chronological > In The Hills 2024-12

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