Rasp fern Blechnum zeelandicum

Many of New Zealand’s threatened ferns are found in warmer climates on landmasses north of New Zealand, with New Zealand representing their southern distribution limits. These species tend to be restricted to northern areas of the country and occupy coastal and geothermal sites. Other species are restricted to habitats such as wetlands, which have suffered drastic modification and loss, or are palatable to stock and feral animals.

Key Features

  • Short terrestrial fern with bright green, strap-shaped fronds that are pink when young and up to 50 cm long at maturity. Fronds are of two types: sterile fronds are more or less prostrate, harsh, lack sori and have relatively broad leaflets, while fertile fronds are erect with narrower, spore-bearing leaflets. The lowermost leaflets are attached to the frond axis by stalks, and the terminal leaflet on fertile fronds is much longer than the other leaflets, distinguishing this species from the related B. molle. In addition, the frond axis is hairy in B. molle, but without hairs in B. zeelandicum.
  • These species could be confused with the related B. fluviatile, which also has prostrate sterile fronds and erect fertile fronds, but B. fluviatile fronds are arranged in a tight rosette rather than a loose cluster, and have more rounded leaflets than B. molle and B. zeelandicum.

Distribution and Habitat

  • Sparsely distributed in the North Island from northern areas to Porirua.
  • Most localities are coastal but B. zeelandicum is occasionally found inland on lowland sites, particularly thermal areas. The habitat is rocky areas in forest and scrub and on river banks.


  • Habitat modification and loss.
  • Competition with exotic plants.

Management Opportunities and Methods

  • Survey for new locations.
  • Protection of habitat.
  • Weed control.

Monitoring Options

  • Check existing populations annually.
  • Report new locations to DOC, NZPCN.

Further Information and Support

  • New Zealand Plant Conservation Network (NZPCN). http://www.nzpcn.org.nz
  • Weed management - Department of Conservation, Regional Councils.
  • References
    • Brownsey, P.J. & Smith-Dodsworth, J.C. (2000). New Zealand Ferns and Allied Plants. David Bateman, Auckland.
    • Perrie, L.R.; Wilson, R.K.; Shepherd, L.D.; Ohlsen, D.J.; Batty, E.L.; Brownsey, P.J.; Bayly, M.J. (2014). Molecular phylogenetics and generic taxonomy of Blechnaceae ferns. Taxon 63(4): 745-758.