The effects of induced plant injury on leaf lobation of red mulberry (Morus rubra L.) were studied in 1990, 1991, and 1992 at Bowling Green, Kentucky. Injury treatments consisted of complete defoliation of sprouts and saplings and trunk and branch removal from saplings. Pre- and post-injury lobation means were compared. In general, leaf defoliation (only) resulted in new flushes of leaves that were less lobed, whereas leaf defoliation plus stem and branch removal resulted in the production of adventitious branches with new flushes of leaves that were more lobed. This leaf lobation response to plant injury was interpreted as being of adaptive value to the plant. The resulting stress morphology was attributed to phenotypic plasticity of leaf lobation.