Abstract Theophrases (285 bc ) and later Pliny recognized the existence of ‘interference’ among plants and noted it significance in agriculture. However, involvement of plant-produced chemicals in plant-plant interactions was first suggested by the Swiss botanist M.A.-P. de Candole in 1832. This was later emphasized by Hoy and Stickney in 1881, who observed the effect of black walnut ( Juglans nigra ) on surrounding vegetation. Years later (1973), Molisch coined the term allelopathy to include both harmful and beneficial biochemical interactions between all types of plants and interactions involving microorganisms. This definition was later adopted Rice (1983) and is accepted at the present time.