In The Hills In The Hills 2016-09

Blechnum penna-marina < Species index > Brachyglottis repanda

This article was first published in the Tararua Tramper Volume 88, no 8, September 2016

September in the hills with Barbara Mitcalfe and Chris Horne

Blechnum vulcanicum, korokio, mountain hard fern

This fern derives its name from the volcanic region in Java where it was first collected. Found in the North, South, Stewart and Chatham islands, it is also in Australia, New Guinea, Indonesia, Philippines and elsewhere in the Pacific.

In NZ, korokio is much more common in the lowland and montane areas of the South Island than in the North Island, where you may find it in scattered localities in lowland and montane areas. Wellington trampers are more likely to see this fern out in the open, on banks and in road cuttings, but not often in forest. Listed below are Wellington sites where Chris and I have seen it.

Blechnum vulcanicum – sterile fronds, plus some fertile fronds. Photo: JEREMY ROLFE

The rhizome is more often erect than creeping. The sterile fronds are light green; up to 35x14 cm, elliptic or narrowly triangular in shape, with a slightly harsh texture and hairs on the underside. The segments are in 10–25 opposite pairs, with the longer pairs nearer the base of the frond. You will see that the segments have no 'stalks' so they are described as 'adnate',which means 'attached to the frond's rachis by their own whole width'. Their margins are finely serrated, and may be pointed or blunt-ended. The most obvious and useful clue to identify korokio, is that the basal pair of segments points distinctly downwards, like an inverted 'v' (see image). This makes korokio easy to identify.

The fertile fronds are c.40 cm long, with scales at the base of the stipe (stem). As the frond matures, its many pairs of fine, linear, (very skinny) pairs of segments develop sori, (similar to e.g., Blechnum filiforme), and begin the process of reproduction. For identification, the basal pair of segments points downwards in an inverted 'v', just as the segments on the sterile fronds do.

Some Wellington sites

If you are tramping in the Wellington area, look for korokio on banks beside Hawkins Hill Road, as well as in the Waipapa and Waiariki valleys and Spooky Gully, and in the west, on Outlook Hill. It also occurs in East Harbour Regional Park, e.g., on Muritai and McKenzie tracks, and the upper Wainuiomata and Ōrongorongo valleys. Please let us know if you find korokio anywhere else.

Uses

We have not found any references to rongoā (medicinal) or other uses, for korokio.

See also

Category

Botany 2016

In The Hills 2016-08 < Index chronological > In The Hills 2016-10