Adiantum formosum
Common names
giant maidenhair, plumed maidenhair
Biostatus
Native
Category
Vascular
Structural class
Ferns
Detailed description
Tall, widely creeping fern forming 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 × 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.
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 Manawatū Gorge, and in forest near the eastern and western ends, as well as around Woodville.
Also 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.
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2023 | At Risk – Relict | Qualifiers: RR, SO
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.
Detailed taxonomy
Genus
Family
Synonyms
None
Endemic taxon
No
Endemic genus
No
Endemic family
No
Ecology
Life cycle and dispersal
Minute spores are wind dispersed (Thorsen et al., 2009).
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.
Other information
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’
NVS 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.
ADIFOR
Chromosome number
2n = 116
Previous conservation statuses
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | At Risk – Relict | Qualifiers: RR, SO
2012 | At Risk – Relict | Qualifiers: RR, SO
2009 | At Risk – Relict | Qualifiers: SO, RR
2004 | Non-resident Native – Vagrant
Referencing and citations
References and further reading
Bostock PD. 1998. Adiantaceae. Flora of Australia 48, Ferns Gymnosperms and allied groups: 248–263. ABRS/CSIRO Victoria, Australia.
Thorsen MJ, Dickinson KJM, Seddon PJ. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 11: 285–309. https://doi.org/10.1016/j.ppees.2009.06.001.
Attribution
Fact Sheet Prepared for NZPCN by P.J. de Lange (Updated July 2004). Description adapted from Bostock (1998).