Allelopathic effects of aqueous leaf extracts of 10, 20, 30, 40 and 50 g/l six tree species (Juglans regia, Quercus cerris, Populus tremula, Pinus nigra, Platanus orientalis and Salix alba) on seed germination and seedling growth of 2 turf species were investigated. All the extracts tested had generally inhibitory effects on seed germination of turf species Lolium perenne and Festuca arundinacea as compared with control. This inhibition effect increased with increasing extract concentrations. Seed germination was less affected than root and shoot elongation in all species. However, 10 g/l treatment of Populus tremula, Pinus nigra and Platanus orientalis promoted root and shoot elongation of turf species. These results indicate that some tree leaves (Juglans regia and Salix alba) contain water-soluble allelochemicals which have more inhibitory effect than other species on turf species.