An erect plant with a dull green stem bearing 12 to 30 strong longitudinal ridges. Inflorescence always compact and dark red brown.

A form of Juncus effusus has a compact inflorescence

Stems strongly ridged, but less so than hard-rush, and not greyish; inflorescence compact

Photo showing plant in its habitat, and detailed photo showing ridged stem and inflorescence

Damp grassland, marshes, bogs and wet open woods.

June to August.

Perennial.

Fairly common throughout Britain.

Fairly common in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 278 of the 617 tetrads.