Cyperus pennatiformis, a member of the Cyperaceae (sedge) family, is a short-lived perennial plant with a woody root system covered with brown scales. The stout, smooth, three-angled stems are between 0.4 and 1.2 m (1.3 and 4 ft) long, slightly concave, and 3 to 7 mm (0.1 to 0.3 in) in diameter in the lower part. The 3 to 5 linear, somewhat leathery leaves are 8 to 17 mm (0.3 to 0.7 in) wide and at least as long as the stem. Each flower cluster, umbrella-shaped and moderately dense, is 4 to 15 cm (1.5 to 6 in) long and 5 to 25 cm (2 to 10 in) wide. About 5 to 18 spikes (unbranched, elongated flower stalks), comprised of numerous spikelets (elongated flower-clusters), form each cluster. Each spikelet, measuring about 8 to 14 mm (0.3 to 0.6 in) in length, is yellowish brown or grayish brown and is comprised of 8 to 25 densely arranged flowers. The glumes (bracts beneath each flower), which are less than twice as long as wide, are spreading and overlap tightly. The lowest glume does not overlap the base of the uppermost glume.