Adiantum diaphanum


Adiantum: From the Greek a- 'without, lacking' and diantos 'moistened', the fronds of this fern are supposed to remain dry after submersion in water
diaphanum: From the Greek diaphanes, meaning transparent or filmy

Common Name(s)

Tuberous maidenhair, Small maidenhair

Current Conservation Status

2012 - Not Threatened

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 - Not Threatened
2004 - Not Threatened


Adiantum diaphanum Blume



Flora Category

Vascular - Native

NVS Species Code


The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.

Structural Class



Adiantum setulosum J.Smith, A. affine Hook. non Willd., A.polymorphum Colenso, A. diaphanum var. polymorphum (Colenso) Cheeseman, Adiantum tuberosum Colenso


Indigenous. New Zealand: Kermadec (Raoul Island), North, South and Chatham Islands (common from Te Paki to the Waikato otherwise rather local reaching as far south as Dunedin). Also southern China, Japan, Taiwan, Vietnam. Malesia, Australia, Norfolk and Lord Howe Islands and the wider Pacific.


Coastal to lowland in closed or open forest. Often on clay banks, under overhangs, on rubble slopes or along rocky stream sides.


Tufted, terrestrial fern. Rhizomes erect, c.2 mm diameter; scales concolorous, golden brown, with entire margins and prominent apical seta. Roots and rootlets bearing ovoid proliferous tubers to c.1.5 mm long. Fronds tufted, adaxially dark green, abaxially paler, to 360 mm long. Stipe to 180 mm long, smooth adaxially, scabrous abaxially. Lamina 20-170 × 20-130 mm, 1-pinnate, or 2(-3)-pinnate at the base and 1-pinnate above, subpedate, hastate or deltoid, membranous; rachises flexuous, glossy, glabrous. Basal pinna, when present, 1 or 2 (rarely more), narrowly deltoid, 1-2-pinnate. Pinnules dimidiate, rectangular to subtrapeziform, becoming cuneate-flabellate in apical segments, abaxially sparsely to very sparsely setose or glabrous, adaxially glabrous or setose hairy; distal margins shallowly lobed, denticulate when sterile; veins dark brown near stalk, otherwise pale. Sori 1-10 along distal margins, usually 1 per lobe; soral flaps round to subreniform, setose or glabrous, deeply immersed in the lobe. Spores c.64 per sporangium, yellow, perine scabrous; largest diameter (25.6-)33.9(-51.9) microns.

Similar Taxa

Easily distinguished by the tuberous roots and rootlets, and small, sparingly divided frond. It can be confused with diminutive forms of Adiantum hispidulum with which it sometimes grows and from which it is reliably distinguished by the tuberous rootlets.


Not applicable - spore producing

Flower Colours

No Flowers


Not applicable - spore producing

Propagation Technique

Easily grown in a shady site planted in a light, well-drained soil.


Not Threatened

Chromosome No.

2n = 232

Endemic Taxon


Endemic Genus


Endemic Family


Life Cycle and Dispersal

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

Where to Buy

Not commercially available. 


Fact Sheet Prepared for NZPCN by P.J. de Lange (Updated 4 May 2011). Description adapted from Bostock (1998).

References and further reading

Bostock, P.D. 1998: Adiantaceae. Flora of Australia 48: 248-263.

Thorsen, M. J.; Dickinson, K. J. M.; Seddon, P. J. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 2009 Vol. 11 No. 4 pp. 285-309

This page last updated on 10 May 2014