Scirpus crassiuscula (Hook.f.) Benth., Scirpus crassiusculus
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.
2n = c.64
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 | At Risk – Naturally Uncommon | Qualifiers: RR, SO
Previous conservation statuses
2012 | At Risk – Naturally Uncommon | Qualifiers: RR, SO
2009 | At Risk – Naturally Uncommon | Qualifiers: SO
2004 | Range Restricted
Indigenous. North Island, Central Volcanic Plateau from the upper Rangitoto Range and Kaingaroa Plain south to the northern Ruahine Range and Waiouru area. Also present in Australia and New Guinea
An upper montane - alpine (700 - 1500 m a.s.l.) sedge of bogs, mires, pond, tarn and stream margins. Sometimes found wholly aquatic in deep pools, ponds or slow flowing streams.
Wetland plant indicator status rating
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
A densely tufted yellow-green to glaucous green sedge. Terrestrial plants rather dense, more or less compact tufts 60-150 mm diameter, aquatic forms forming floating mats up to 1 m long in slow flowing water. Rhizome much elongated, branched and rooting at nodes. Culms 20-200 x 1-2 mm, usually rather rigid, less so in aquatic plants, erect, very leafy. Leaves 40-60 x 1-1.5(-2) mm, less than, equal to or greater than culms, narrow-linear, lamina flattened, apex subobtuse; lowermost leaf on branch bract-like with pale membranous sheath up to 6 mm wide. Inflorescence a very stout, solitary,pale-green, flecked with red, terminal spikelet (rarely 2 spikelets), subtending bract absent. Spikelets 3-10 x 2-8 mm, usually rather squat, ovoid or oblong (more usually in aquatic or partially submerged plants). Glumes 2-4 mm, broadly ovate, obtuse, finely nerved, centrally green otherwise red-purple to very dark red-purple towards margins, margibns often a well marked as a wide hyaline band. Hypogenous bristles 0. Stamens 3. Style-branches 2. Nut 1.5 x 1 mm, grey, obovate, compressed, margins distinctly thickened, minutely apiculate.
A very distinctive sedge which is well marked from the other New Zealand Isolepis by its very thick set, leafy and very chunky yellow-green to glaucous green culms, and rather squat, ovoid, usually solitary terminal spikes. However, aquatic forms can be confused with both varieites of I. fluitans (L.) R.Br. From that species, I. crassiuscula can be recognised by having 3 rather than 2 stamens, and spikelets which are 2-8 rather than 1-2 mm wide. Unlike either variety of I. fluitans in which it is always present, the spikes of Isolepis crassiuscula lack a subtending bract.
November - March
November - April (-May)
Nuts are dispersed by water and possibly granivory and attachment (Thorsen et al., 2009).
Easily grown from rooted pieces and fresh seed. Should be planted in a permanently damp, peaty soil, or in a pot kept partially submerged. May be grown under water, and might be ideal as a fish tank plant or pond weed for an outdoor water feature.
A rather widespread species which can be locally abundant in parts of its central North Island range. It does not seem to be as vulnerable to weed species, such as Juncus bulbosus L. as some other wetland plants of this region (e.g., Schoenus fluitans Hook.f., Isolepis fluitans (L.) R.Br.), and it may in fact not qualify for a conservation assessment in future listings.
isolepis: From the Greek isos (equal) and lepis (scale)
Where To Buy
Not commercially available.
Description adapted from Moore and Edgar (1970)
References and further reading
Johnson, A. T. and Smith, H. A (1986). Plant Names Simplified: Their pronunciation, derivation and meaning. Landsman Bookshop Ltd: Buckenhill, UK.
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