Cyperus polystachyos Rottb.
Densely tufted annual to perennial. Stems to 50 cm tall, 3-angled, leafy at base. Leaves < stems, 2-3 mm wide, smooth; sheaths purple-brown, sometimes with a few transverse septa. Involucral bracts 3-6, leaf-like, > inflorescence. Inflorescence capitate or with rays to 4 cm long. Spikelets ± stiffly erect in rather dense clusters, narrow-linear, acute, ± 15 × 1.5 mm. Glumes ± 2 mm long, densely imbricate, membranous, subobtuse, chestnut or straw-coloured with green keel. Stamens 2. style-branches 2. Nut ± ½ length of glume, oblong, compressed-biconvex, brown.
N. North Auckland - southwards to Kaitaia, Hokianga, Silverdale. In wet land and pastures, apparently increasing. (Widespread in tropics and subtropics, also in more temperate regions of Australia)
First record: Healy 1957: 652.
First collection: "Motutangi, Northland, spreading rapidly in pasture" W. Metcalfe, 2 July, 1953 (CHR 82617).
Luxuriant forms of this sp., almost certainly perennial, might be confused with slender states of C. eragrostis, but can be recognized by the more compact chestnut-brown inflorescences and linear spikelets.
A weedy tufted plant increasing in poor pastures, waste places, cultivated land, stream banks, and about lakes and swamps. It is probably more widely distributed and abundant than is at preset known.