Symbiotic alders are potential candidates for use in the remediation and revegetation of oil sands reclamation sites, and greenhouse inoculation has been shown to help ensure successful out-planting in the field. For successful nodule formation and growth, the time of inoculation (plant age) and N input are factors to be considered. In the present study, symbiosis was induced between Alnus crispa and Frankia strain AvcI1. Seedlings were grown, inoculated and exposed to different growing conditions that consisted of combining the presence or absence of Frankia, three different plant ages and five N treatments, to determine the best method for enhancing plant nodulation and growth. Results indicated that inoculation of 9-week-old seedlings with Frankia improved seedling growth, promoted nodule formation and ensured efficient N2 fixation. Fertilization with 100ppm of N was counterproductive for plant health, while the lower concentration of N, 10ppm, did not fulfill the N requirements of seedlings, suggesting the need to apply higher concentrations of N that do not surpass 100ppm. Greenhouse inoculated alders were subsequently used in a large-scale field trial to evaluate their ability to improve soil quality and metabolic activity of the indigenous microbial community in an oil sands reclamation site. In addition, the inoculated Frankia was monitored to determine if it remained present as part of the endophytic community in alder nodules. Results showed that inoculated alders were capable of very active growth, out performing non-inoculated plants, producing up to five-fold more biomass within the 3 growing season monitoring period. Alders also promoted the proliferation of heterotrophic and hydrocarbon degrading bacteria in the rhizosphere. Indigenous Frankia strains, that shared molecular similarities with the symbiont used in this study, were found in the nodules of non-inoculated alders, as well as in some of the soil samples indicating that a molecular detection approach requires further validation.