This southeastern annual occurs mostly on the Coastal Plain along shorelines of stagnant waters; 2n = 36, 72. See notes on habitat under Oldenlandia boscii. Edrastina uniflora differs from Oldenlandia boscii as follows (W): stem pilose or villous or rarely glabrous (versus glabrous or nearly so); leaves mostly ovate or broadly lanceolate (versus mostly linear or linear-lanceolate), 4-10 mm wide, generally with L/W = 2-3 (versus 1-3 mm wide, generally with L/W = 5-10); flowers in compact clusters of 3-10 or rarely solitary (solitary or rarely 2-3); plants annual (versus pennernial).