Gahnia robusta Kirk; Gahnia rigida Kirk car. robusta (Kirk) Benl
Vascular – Native
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.
Current conservation status
The threat classification status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2017 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants. Authors: By Peter J. de Lange, Jeremy R. Rolfe, John W. Barkla, Shannel P. Courtney, Paul D. Champion, Leon R. Perrie, Sarah M. Beadel, Kerry A. Ford, Ilse Breitwieser, Ines Schönberger, Rowan Hindmarsh-Walls, Peter B. Heenan and Kate Ladley. Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – a suggested threat classification status has not been assessed by the NZTCS panel.
2017 | Not Threatened
Previous conservation statuses
2012 | Not Threatened
2009 | Not Threatened
2004 | Not Threatened
Endemic. North (near Pureora, Mamaku Plateau, Mangaroa Swamp) and South Islands (western Nelson and Westland to about Haast).
Coastal to lowland in swamps, bogs, mires and pakihi - often forming the dominant cover.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland).
FACW: Facultative Wetland
Usually is a hydrophyte but occasionally found in uplands (non-wetlands).
Robust perennial sedge arising from a stout, lignaceous rootstock and forming dense yellow-green tussocks 0.6-2.2 m tall. Culms 4-6 mm diameter (but up to 10 mm diameter near base). Leaves up to 3 m long, mostly erect with apices slightly drooping; sheaths dull pinkish brown, open, often frayed or shattered up to 50 mm wide at the base; lamina very hard, scabrid right across undersides, margins strongly involute when dry, scabrid; lamina when dry becoming undulate for some distance above the transverse line demarcating sheath from lamina. Panicle rigid, 18–760 x 60 mm, bearing numerous stiffly erect branchlets, primary branchlets up to 250 mm long. Spikelets 2-flowered, 6-7 mm long, stalked, light chestnut-brown to dark brown. Glumes 6-7; 3-4 outer glumes 6-7 mm long, empty; 3 inner glumes enclosing fruit brown. Stamens 4-5. Style-branches (2-)4. Nut 3.5-4.0 x 1.5-2.0 mm, ellipsoid-obovoid, usually light red-brown with a band of dark brown round the centre or the upper half dark brown, occasionally dark brown at the base and apex and then almost black at the centre, tipped with a fine scabrid point; endocarp transversely grooved within.
Gahnia rigida could only ever be confused with the other giants of the New Zealand species G. setifolia (A. Rich.) Hook.f. and G. xanthocarpa (Hook.f.) Hook.f. Gahnia rigida rarely grows with either of these species. Gahnia xanthocarpa differs from G. rigida by its glossy light to dark green leaves, drooping rather than rigidly erect panicles, and dark glossy black nuts. Gahnia setifolia differs from G. rigida also by its drooping rather than rigidly erect panicle and reddish brown nuts. The nuts of G. rigida are diagnostic being the only ones to be consistently bicoloured light red-brown/dark brown, or dark brown with a broad black central band present
December - March
Fruits may be found throughout the year
Florets are wind dispersed (Thorsen et al., 2009).
Can be difficult to cultivate. The seed is difficult to germinate, and plants resent root disturbance and usually die if transplanted. However, considerable success has been achieved growing plants and/or germinating seed in untreated saw dust. Despite these problems this is an attractive species well worth attempting to grow. Once established it flourishes in a range of conditions though it does best in full sun in an acidic, poorly drained soil.
gahnia: After Gahn
Fact Sheet prepared by P.J. de Lange (30 October 2005). Description adapted from Moore and Edgar (1970)
References and further reading
Moore, L.B.; Edgar, E. 1970: Flora of New Zealand. Vol. II. Government Printer, Wellington.
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 11: 285-309
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Gahnia rigida Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/gahnia-rigida/ (Date website was queried)