Pinno, B. D., Landhäusser, S. M., MacKenzie, M. D., Quideau, S. A. and Chow, P. S. 2012. Trembling aspen seedling establishment, growth and response to fertilization on contrasting soils used in oil sands reclamation. Can. J. Soil Sci. 92: 143-151. Trembling aspen (Populus tremuloides) is an important tree species for land reclamation. This study determined trembling aspen germination, establishment, initial growth and response to fertilizer on contrasting oil sands reclamation soils. In a greenhouse, eight soils varying in total nitrogen and available phosphorus were treated with no fertilizer (control), phosphorus and potassium (PK), nitrogen (N) and all three (NPK). Soil had the greatest impact on aspen growth when no fertilizer was applied with the best growth occurring on organic-mineral material soils where growth was positively correlated with extractable and foliar potassium but not to nitrogen or phosphorus. With PK and N fertilizer, growth increases were positively correlated with foliar phosphorus concentrations of the corresponding controls. NPK fertilizer caused greater growth, bud set and root:leaf mass ratio compared with PK or N fertilizer. Soil type had little impact on germination and establishment, indicating natural aspen seedlings can potentially regenerate on all of these soils. In oil sands mining reclamation where these soils are used as surface materials, organic-mineral mixes had the greatest potential without fertilizer. With fertilizer, NPK provided maximum growth and developmental benefits.