“…Annual ragweed, which is invasive in Europe (Beres et al, 2002), produces phytotoxic phenoloids and terpenoids that inhibit germination and seedling growth of several cultivated species (Bruckner, 1998). Annual ragweed root exudates and shoot extracts also inhibit germination and growth of earlyseral species, but not later-seral species, in native North American habitats (Jackson & Willemsen, 1976). Common sunflower, which is naturalized in Europe (Faure et al, 2002), also produces a number of phytotoxic compounds that inhibit a variety of plant species (Azania et al, 2003;Beres & Kazinczi, 2000;Irons & Burnside, 1982;Leather, 1983;Macias et al, 1998;Macias et al, 1998;Maruthi & Sankaran, 2001;Morris & Parrish, 1992;Ohno et al, 2001), including early-seral species, but not later-seral species, in native North American habitats (Wilson & Rice, 1968).…”