Cyperus congestus Vahl

Thickly tufted perennial. Stems 15–40–(80) cm high, rather robust, 3-angled, smooth, leafy and somewhat bulbous and woody at base. Leaves usually < stems, to 7 mm wide, flat, margins smooth below, scabrid towards tip; sheaths purple-brown, minute transverse septa evident. Involucral bracts 3–6, leaf-like, the lowest > inflorescence. Inflorescence a simple or compound umbel or reduced to a single head; rays 2–4, rather rigid, to 6 cm long. Spikelets numerous, 10–20 × 2 mm, narrow-linear, acute, in dense ovate or hemispherical reddish-purple spikes; rhachilla with membranous wings. Glumes ± 3 mm long, not closely imbricate, usually tightly appressed to rhachilla, oblong-elliptic, acute, many-nerved, keel green, margins deep red-purple. Stamens 3. Style-branches 3. Nut ± ½ length of glume, obovoid-oblong, trigonous, dark brown, apiculate.

[From: Healy and Edgar (1980) Flora of New Zealand. Volume 3.]