Les Abattes (Le Locle, Canton Neuchâtel) is an ancient dump contaminated by metals, like thousands of others in Switzerland, which, according to the law, does not require a reclaiming. Local trees have been grown on this site and data have been collected for 15 years between 1991 and 2005. Lessons grown from this experience are mixed. The plantation has stabilised the soil physically and immobilised the metals more rapidly than natural pioneer plants would. However growing trees have not been able to extract enough metals from soil. The risk of a diffuse metal contamination of surface water and food chain is still present. Therefore reforestation of low-contaminated sites has to be seen as a temporary solution requiring a continuous supervision in a longterm. At best it could provide timber under certain conditions. It is recommended to clearly indicate these constraints in the forest guiding plans which are now being elaborated.