Current practice in Ontario for planting tree seedlings is to place the root collar level with the soil surface. There is evidence that deeper planting can improve performance of certain tree species, and this report reviews 11 relevant studies of deep planting of jack pine, black spruce, white spruce, and other North American conifers. Explanations, as described in the literature, of environmental & biological consequence are provided and current planting practices are described. Finally, the current findings as they applied to the above three species are summarized.