Couch paspalum

Paspalum distichum, the couch paspalum, knotgrass, or salt-water couch, is a stoloniferous perennial grass in the family Poaceae with a near-cosmopolitan distribution across warm-temperate, subtropical, and tropical regions, where it grows in damp ground at the margins of ditches, ponds, brackish marshes, riverbanks, and irrigated rice paddies. The plant produces strong creeping stolons that root vigorously at the nodes, forming dense low mats that can colonize wet bare ground rapidly. From the stolons arise erect to ascending flowering culms 15-60 cm tall. The leaf blades are flat, linear-lanceolate, 5-15 cm long and 3-8 mm wide, hairless to sparsely hairy at the base, with a short, membranous ligule. The diagnostic inflorescence consists of typically two (rarely 3-4) digitate slender spike-like racemes 3-8 cm long, borne at the top of the culm in a distinctive V or inverted-T configuration, with the racemes ascending or somewhat spreading. Spikelets are arranged in two rows along one side of the flattened rachis, each elliptic, 2.5-3.5 mm long, and silvery-puberulent on the lower glume. The species is an important forage grass on wet ground but is also a serious weed of waterlogged crops in many parts of the world.