Bolboschoenus caldwellii


Bolboschoenus: From Greek: bolbos (swelling or bulb) and schoinos (rush, reed), from the supposed difference from the genus Schoenus in having bulbous tubers

Common Name(s)

Purua grass, Caldwells clubrush

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


Bolboschoenus caldwellii (Cook.) Soják



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



Scirpus caldwellii Cook.


Indigenous. North Island from the Kaipara Harbour south, and mainly easterly. In the South Island widespread from Nelson to Otago, mainly eastern. Also in Australia.


Coastal to lowland in saltmarshes and other poorly drained saline areas. Sometimes invades pasture abutting tidal streams and estuaries.


Summer-green, bulbous perennial forming mostly densely clumped patches. Rhizome 3-5 mm diameter, horizontal, long-creeping, brown, apices terminated by globose, ligneous tubers. Culms 1(-3) per tuber, 0.3-1.0 m tall, 2-3 mm diameter, triquetrous; basal sheaths 1-2, mostly membranous, with a short channelled lamina. Leaves numerous, <, equal to, or > culms, 200-320 x 2.5-4.0 mm, double-folded but flattened, grass-like, tapering, coriaceous, margins and midrib scabrid towards apices; sheaths short, closed, coriaceous. Inflorescence a terminal, compact head of 3-6 spikelets; rays if present 1-3, 10-40 mm long, unequal, subtending involucral bracts similar to leaves, > inflorescence, unequal, 40-220 x 1.5-2.5 mm. Spikelets 10-20 mm long, ovoid or cylindric, red-brown. Glumes membranous, pubescent, apices slightly cleft or lacerate, with a scabrid, slightly recurved awn. Hypogynous bristles 6, unequal, about half length of nut, deciduous, red-brown, retrorsely scabrid. Stamens 3. Style-branches 2. Nut 3.5-4.0 x 2.5 mm, biconvex or obovoid, compressed, with a small depression on each side, smooth, apiculate, maturing cream to dull brown and glossy.

Similar Taxa

Differs from B. fluviatilis (Torr.) Soják and B. medianus (Cook) Soják by the smaller size, often glaucescent leaves, fewer subsessile to very shortly stalked spikelets, consistently 2 style branches, and circular, biconvex nut with distinctly concave (depressed) sides


October - January


December - May

Propagation Technique

Easily grown from fresh seed and rooted pieces. Will grow in almost any soil but prefers a sunny, damp soil. Ideal as a pond plant or for planting along tidal streams.


Not Threatened but uncommon in northern part of range

Endemic Taxon


Endemic Genus


Endemic Family


Life Cycle and Dispersal

Bristly nuts are dispersed by water and possibly wind (Thorsen et al., 2009).

Where To Buy

Not commercially available


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 2009 Vol. 11 No. 4 pp. 285-309

This page last updated on 14 Aug 2014