Slender bulrush is an emergent aquatic graminoid, 1-3m tall, with hard and slender stems and scales with short, red-brown lines on a usually tawny background. It has a loose and lax inflorescence, most or all of the spikelets are individually pedicellate. Spikes are light to medium brown, most flowers have three carpels, styles are 3-parted. Its achene are unequally three-angled. It has few leaves, most or all towards the base, commonly with prominent, well developed sheaths and short, poorly developed (or no) blades.