The New Zealand Plant Conservation Network

Species

Bolboschoenus medianus

Etymology

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

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

Authority

Bolboschoenus medianus (Cook) Soják

Family

Cyperaceae

Flora Category

Vascular - Native

NVS Species Code

BOLMED

Structural Class

Sedges

Synonyms

Scirpus medianus Cook

Distribution

Indigenous

Habitat

Coastal to lowland in saltmarshes and other poorly drained saline areas, occasionally found along freshwater rivers and lakes. Sometimes invades pasture abutting tidal streams and estuaries.

Features

Summer-green, bulbous perennial forming mostly densely clumped patches. Rhizome 3-5 mm diameter, woody, horizontal, long-creeping, dark brown, apices terminated by globose, ligneous tubers. Culms 1(-2) per tuber, 0.7-1.5 m tall, 4-5 mm diameter, triquetrous, striated, smooth except just below inflorescence where scabrid on angles; basal sheaths loose, membranous, septate, brown. Leaves numerous, more or less equal to, or greater than culms, 450-500 x 6-8 mm, double-folded but flattened, grass-like, tapering, coriaceous, margins and midrib scabrid towards apices; sheaths long, closed, coriaceous. Inflorescence a terminal, compound, irregular umbel; rays 4-6, unequal, 20-100 mm long, bearing clusters of 1-6 spikelets, a sessile glomerule of spikelets at the base of the rays; involucral subtending bracts similar to leaves, greater than inflorescence, unequal, 150-250 x 3-6 mm, as many as, or 1-2 fewer than rays. Spikelets 10-20 mm long, ovoid, or more or less cylindric, dull red-brown. Glumes membranous, pubescent, apices cleft or lacerate, with a scabrid, recurved awn. Hypogynous bristles up to 6, in length < nut, persistent or shedding, red-brown, retrorsely scabrid. Stamens 3. Style-branches 2-3. Nut 3.0-4.0 x 2.0-2.5 mm, obovate, dorsiventrally compressed and plano-convex or trigonous with obtuse dorsal angle and convex sides, apiculate, maturing greyish to black and glossy.

Similar Taxa

Distinguished from the other two indigenous species, B. caldwellii caldwellii (Cook.) Soják and B. fluviatilis (Torr.) Soják by the nuts with are compressed rather than trigonous (as in B. fluviatilis) and with convex rather than depressed (concave) sides (as in B. caldwellii) and by the 2-3 style branches, rather than consistently 2 in B. caldwellii or mostly 3 in B. fluviatilis.

Flowering

October - January

Fruiting

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.

Threats

Not Threatened

Endemic Taxon

No

Endemic Genus

No

Endemic Family

No

Life Cycle and Dispersal

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

This page last updated on 14 Aug 2014