In The Hills In The Hills 2016-04

Blechnum colensoi < Species index > Blechnum filiforme

This article was first published in the Tararua Tramper Volume 88, no 3, April 2016

April in the hills with Chris Horne and Barbara Mitcalfe

Blechnum discolor, crown fern, piupiu

Crown fern / piupiu Photo: Jeremy Rolfe

There are about twenty members of this fern genus in New Zealand. A striking feature of all Blechnum species is that their fertile fronds and sterile fronds usually look different from each other, with the fertile fronds being much narrower. The fertile fronds grow in the centre of the plants, with two lines of sori on the undersides of their narrow segments.

The name Blechnum is derived from the Latin word for ferns; discolor refers to the “two-coloured” feature of the sterile fronds - their upper and lower surfaces are differently coloured.

Distribution

Crown fern is endemic to New Zealand. It is common in drier lowland to montane forests, usually at higher elevations in the North Island. You can see it on the North, South, Stewart/ Rakiura, Chatham/Rekohu, Auckland and Campbell islands.

Form

Crown fern often forms woody trunks up to c.30 cm tall. The sterile fronds rise and spread out like a crown, while the stiffly upright fertile fronds grow up from the centre of the plant. The stalks of the sterile fronds are 5-16 cm long. The upper parts of the sterile fronds are 20-100 x 5-16 cm, bright green above, and much paler below.

If deer, goats or possums are numerous in the vicinity, crown fern may flourish because these pest animals rarely eat piupiu's harsh fronds. It often forms extensive patches in open beech forest and in scrub, because it spreads by means of runners. It often out-competes other plant species. You may have waded through such dense communities of it in shorts, that you are sure to have felt the rough texture of the sterile fronds!

Reproduction

The fertile fronds are slightly taller than the sterile fronds. The sori, in which the spores develop, are in continuous lines along both sides of the midrib of the fertile fronds. When ripe, the spores are distributed by the wind.

Uses

The light colour of the underside of the fronds shows up clearly in daylight, as well as in the light of your torch. You can turn over the ends of crown fern's sterile fronds to point out a temporary route. For example, you can turn them over to mark the route from your tent site to your toilet trench, or to the nearby creek. In order to implement the Minimum Impact Code, before you break camp, you have merely to unbend the fronds, and no one will know that you have been there.

See also

Category

Botany 2016

In The Hills 2016-03 < Index chronological > In The Hills 2016-05