Pruning trees will not speed up growth. In fact pruning off the lower limbs may actually slow the rate of growth. The growth rate of trees is dependent on the amount of leaf surface present and on genetic factors. A great part of the growth is determined by the genetic potential for growth in the tree. Secondly, leaves manufacture food for plant growth. The more leaves that are cut off the plant, the slower the plant will grow. Therefore, to promote rapid growth leave as many branches and twigs on your young tree as possible. Pruning in the early years should be restricted to guiding tree growth, i.e., if a side branch is tending to become dominant, prune the tip off to promote branching and return dominancy to the top leader. You may also have to brace the leader to ensure that it continues to grow straight up. Side branches should be removed only when they become ¾ to 1 inch in diameter, so that trunk scars (wounds) will heal over quickly.