Tufted, shortly rhizomatous perennial. Culms erect, 20–100 cm high. Leaves cauline and sub-basal; blade hollow, with ± conspicuous transverse septa, shorter than or equalling culms, compressed or terete, 0.7–4 mm wide, apex acute or obtuse; auricles obtuse, to c. 5 mm long. Inflorescence of (3–)7–50(–100) discrete (usually distant) clusters, each composed of (3–)10–35 tightly aggregated flowers, 5–10 mm wide in fruit; primary bract often without a blade-like lamina, much shorter than the inflorescence; prophylls absent. Tepals curved, soft, midrib pale-brown to brown, margins pale, scarious; outer tepals 2.0–3.5(–5.0) mm long, acute; inner shorter than outer, acute; stamens 6, anthers 0.3–0.7 mm long. Capsules pale brown to blackish, darker near the apex, trigonous-ellipsoid to obovoid, c. 2.0–3.5 mm long, subequal to inner tepals, apex obtuse to bluntly acute, often inflexed; seeds c. 0.4–0.5 mm long x c. 0.2 mm wide, very fine longitudinal and transverse ridges discernible at moderately high magnification, minutely apiculate at one or both ends.
VVP, CVU, DunT, HSF. Also naturalised in ? WA, NSW. Native to Central and South America.
In Victoria known only from a single collection from 2009, collected along Yarra River, at Millgrove.
Juncus microcephalus is very similar to, and often confused with J. pallescens. Mature specimens are necessary to distinguish the two species with certainty. Juncus pallescens has an inflorescence with ultimate branches thicker than 0.45 mm (just below the flower heads), and tepals are deep brown. Juncus microcephalus can be distinguished by its generally larger habit, inflorescences that are long-branched, with many discrete clusters of flowers, soft textured tepals that are distinctly unequal in length, the innermost being shorter, and the same length as the capsule. Juncus microcephalus has in most cases been widely misapplied to J. pallescens in Australia.
