Allelopathic interference of the exotic naturalized Paspalum dilatatum Poir. threatens diversity of native plants in urban gardens

•Paspalum dilatatum is one of exotic naturalized species in urban gardens in Egypt.•The allelopathic potential of this species was assessed on native weeds of gardens.•This species significantly reduced cover, biomass and diversity of native weeds.•P. dilatatum-infested soils reduced germination and growth of some native plants.•These soils contained greater contents of phenolics and flavonoids.