A natural phenomenon of release of secondary metabolites by plants or micro-organisms in the environment, normally termed as allelopathy, assumes a significant role in different managed forestry systems. A large number of trees have been reported to exhibit this phenomenon. It influences the successional pattern of the understorey vegetation and the overall dynamics of the ecosystems. In agroforestry systems the allelopathy leads to loss in productivity and changes in the nutrient cycling. The phenomenon could be successfully exploited for the management of weeds and pests apart from understanding and overcoming the problem of soil sickness and conservation of nitrogen etc. It also provides a platform for the scientists of various disciplines to work together.