Greenhouse experiments were conducted to determine the effects of soil enriched in fine tailings (FT), produced by the oil sands extraction, on germination, seedling growth and physiology of several plant species of the boreal forest. The germination of seeds was initially delayed by 15% FT in dogwood (Cornus stolonifera Michx) and jack pine (Pinus banksiana Lamb) but not in white spruce [Picea glauca (Moench) Voss]. In the second set of experiments we showed that all dogwood seedlings survived 6 months of treatment with 15% FT while the survival rates of raspberry, jack pine and white spruce seedlings were reduced to 44, 55 and 94%, respectively. FT reduced root and shoot dry weights in raspberry seedlings and the number of lateral shoots in jack pine and white spruce seedlings. In raspberry and jack pine seedlings, reductions of gas exchange were recorded. The results of our study suggest that the modifications of soil chemistry, texture and structure by FT may all contribute to the observed phytotoxic effects.