Mechanical site preparation methods that used tools mounted on lightweight excavators and that provided localised intensive preparation were tested in eight experimental sites across France where the vegetation was dominated either by (L.) Moench or (L.) Kuhn. Two lightweight tools (Deep Scarifier: DS; Deep Scarifier followed by Multifunction Subsoiler: DS+MS) were tested in pine ( L., var. (Loudon) Hyl. or Aiton) and oak ( (Matt.) Liebl. or  L.) plantations. Regional methods commonly used locally (herbicide, disk harrow, mouldboard plow) and experimental methods (repeated herbicide application; untreated control) were used as references in the experiments. Neighbouring vegetation cover, seedling survival, height and basal diameter were assessed over three to five years after plantation. For pines growing in , seedling diameter after four years was 37% and 98% greater in DS and DS+MS, respectively, than in the untreated control. For pines growing in , it was 62% and 107% greater in the same treatments. For oak, diameter was only 4% and 15% greater in , and 13% and 25% greater in , in the same treatments. For pines, the survival rate after four years was 26% and 32% higher in and 64% and 70% higher in , in the same treatments. For oak, it was 3% and 29% higher in and 37% and 31% higher in . Herbicide, when applied for three or four years after planting, provided the best growth performances for pines growing in and and for oaks growing in . For these species and site combinations, DS+MS and DS treatments reduced the neighbouring vegetation cover for one to four years following site preparation. Molinia caerulea Pteridium aquilinum Pinus sylvestris Pinus nigra corsicana Pinus pinaster Quercus petraea Quercus robur M. caerulea P. aquilinum M. caerulea P. aquilinum M. caerulea P. aquilinum M. caerulea P. aquilinum M. caerulea P. aquilinum P. aquilinum