any blackberry of the genus Rubus (family Rosaceae) so lacking woody fibre in the stems that it trails along the ground. In the eastern and southern United States, several trailing native species of Rubus, especially R. flagellaris, R. baileyanus, R. hispidus, R. enslenii, and R. trivialis, produce excellent fruits. Some varieties, especially Lucretia, are cultivated. See also blackberry.