Knot grass grows in moist to wet areas; wet shores of ponds and streams, and wet prairies. It may also grow along roadsides, in irrigation ditches and canals. It is found throughout Florida and flowers from spring to late fall.
Knot grass is a low, running perennial, with extensively creeping stolons with long internodes. Stems are erect from a horizontal base to 2.5 feet tall. Nodes occasionally have a few hairs; sheaths are glabrous except for long hairs at margin near apex, often long hairs at base. Ligule is white and membranous,to 1.6 mm. Leaf blades are 2-11.5 mm wide, to 14 cm long, tapering to an involute apex, but flat on the creeping stems, glabrous except for long hairs on margin at base and occasional long hairs at base above. Inflorescence usually 2 (rarely 1 or 3) ascending racemes; when terminal, each has a winged rachis bearing solitary white elliptic spikelets, 1-2 mm wide, 2.4-3.2 mm long, first glume usually present, second glume short pubescent with scattered very small fine hairs.
Excerpted from Florida Wetland Plants – an Identification Manual by J.D. Tobe, K. Craddock Burks, et al. Florida Dept. Environmental Protection (1998)