Every tree has it's own unique growth potential. How tall and wide a tree grows is not only determined by its health and the condition of the site, but the final size of a tree will also be determined by it's genetic growth potential. Most good tree guides will give you height and spread information. You need to refer to that every time you plan to plant.
This photo shows a disaster in the making. The oak was planted in a row of Leyland cypress and is dominating the two cypress planted next to it. Unfortunately, Leyland cypress are fast growing and will not only outgrow the oak, they were planted too close to each other and will decline if not pruned radically.
