The New Zealand Plant Conservation Network

Species

Adiantum formosum

Etymology

Adiantum: From the Greek a- 'without, lacking' and diantos 'moistened', the fronds of this fern are supposed to remain dry after submersion in water
formosum: From the Latin formosus 'beautiful'

Common Name(s)

Giant maidenhair, Plumed maidenhair

Current Conservation Status

2012 - At Risk - Relict

Conservation status of New Zealand indigenous vascular plants, 2012
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2012 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2009 and replaces all previous NZTCS lists for vascular plants. Authors: Peter J. de Lange, Jeremy R. Rolfe, Paul D. Champion, Shannel P. Courtney, Peter B. Heenan, John W. Barkla, Ewen K. Cameron, David A. Norton and Rodney A. Hitchmough. File size: 792KB

Previous Conservation Status

2009 - At Risk - Relict
2004 - Non Resident Native - Vagrant

Qualifiers

2012 - RR, SO
2009 - SO, RR

Authority

Adiantum formosum R.Br.

Family

Pteridaceae

Flora Category

Vascular - Native

NVS Species Code

ADIFOR

Structural Class

Ferns

Synonyms

None

Distribution

Indigenous. North Island only, with historic records from near Ahipara (Reef Point), Herekino, and the North Wairoa River near Dargaville. The only extant populations now known occur along either side of the Manawatu River Gorge, and in forest near the eastern and western ends, as well as around Woodville. Present in Eastern Australia (Queensland, New South Wales and Victoria) where it is abundant and under no threat.

Habitat

A species of alluvial forest and gorge sides. Usually found in shaded sites amidst drifts of leaf litter with little (if any) associated vegetation. It rarely grows in full sun.

Features

Tall, widely creeping fern form diffuse patches up to 3 x 1.8 m. Rhizome buried (rarely at surface), long-creeping, much-branched to 10 mm diameter; scales golden brown with an acuminate apex and blunt marginal teeth. Fronds usually widely and irregularly placed along rhizome, up to 1.8 m tall. Stipe up to 0.9 m, wiry, basally dull black, distally glossy black, scabrous, finely tuberculate. Frond lamina 0.15-1 x 0.15-0.9 m, 2-4-pinnate, deltoid to pentagonal, firmly membranous to subcoriaceous; adaxial surfaces of rachises and pinna stalks clad with dense antrorse red-brown hairs. Higher order segments of frond (except pinnules) elliptic or triangular. Primary pinnae progressively reducing in size and degree of branching from base to apex. Pinnules symmetric, flabellate or dimidiate and rectangular to trapeziform, undersides glabrous or sparsely clothed with pale divergent (patent) hairs; distal margins irregularly lobed, dentate when sterile. Sori 1-10 on distal margins only, 1 or 2 per lobe; soral flaps lunate to subreniform, glabrous.

Similar Taxa

Easily recognised by the long creeping usually buried rhizomes, and very tall (up to 1.8 m) 3-4-pinnate fronds.

Flowering

Not applicable - spore producing

Flower Colours

No Flowers

Fruiting

Not applicable - spore producing

Propagation Technique

Easily grown from rooted pieces. Does best in a fertile, free draining, moist but not excessively wet soil in filtered light (semi-shade). Once established specimens should not be disturbed. A very attractive plant which is an excellent subject to plant under tall trees in a woodland garden setting.

Threats

It would appear that this species is spreading vegetatively as preliminary studies on spore germination suggest that while viable spores are produced they cannot germinate within the typical range of New Zealand temperatures (J. E. Braggins & S. Van der Mast pers. comm.). The only known wild populations are thriving but are rather localised and vulnerable to weeds

Chromosome No.

2n = 116

Endemic Taxon

No

Endemic Genus

No

Endemic Family

No

Life Cycle and Dispersal

Minute spores are wind dispersed (Thorsen et al., 2009).

This page last updated on 6 Dec 2014