A stout, robust perennial plant (2) (3), the beaked spike rush (Eleocharis rostellata) has proliferous clustering stems (3) (5), which form distinctive thick tussocks (4). The stems are slender, flattened and leafless (3) (6), with each individual stem ending in a single, cylindrical spike (6) (7). The flowering stems of the beaked spike rush are typically upright (7), while the wiry, non-flowering stems frequently arch downwards, rooting to the ground at the tip to form characteristic dense tufts (4) (5) (6) (7) (8).
The leaves of the beaked spike rush are made up of a grass-like blade and a closed sheath, and are usually arranged in a tuft around the base of the stem (9). The leaf sheaths are generally dark red to brown, becoming increasingly reddish at the tips (8). The small, inconspicuous flowers of the beaked spike rush are arranged in a ‘spikelet’ at the end of the stem (9). Each spikelet contains between 10 and 40 greatly reduced flowers (3) (8), which have very small, dense spines and brownish bristles (8). The blunt, oval-shaped scales of the spikelet are green or brownish, often with a darker vein in the centre of the scale (4) (7).
The beaked spike rush produces a large, single-seeded, greenish to brown fruit, known as an achene, which has a triangular or pyramid-shaped tubercle at the tip (6) (8) (11). The shape of the achene is highly variable (4) (5) (10), and the outer surface of the fruit is typically covered with a network of fine lines (7).
- Length: 0.4 - 1 m (2)