Juncus ensifolius Wikstr.

Loosely tufted or forming open colonies, less frequently densely tufted; rhizome slender, ± far-extending. Stems 15–70 cm high, laterally compressed, almost winged at lower nodes, cauline leaves 2–3. Leaves ensiform, ± curved, ± flat, blue-green, longitudinal and transverse septa visible externally, often incomplete. Inflorescence of 1–3 large, many-flowered, usually blackish, globose clusters, causing taller stems to incline. Tepals 2.5–3 mm long, all ± equal, acute to acuminate. Stamens 3–6. Capsule c. 3 mm long, > tepals, oblong, shortly mucronate, dark brown to black.

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