A tree is best shaped in its first two or three years in the garden. This technique, called formative pruning, will establish an optimum trunk and branch structure and will fix minor problems before they become major ones. It also makes the tree more attractive. We pruned this young redbud (below) to fix its tangled mess of branches and to establish a single trunk, or leader. The work is best done in winter, when you have a clear view of the branches and the tree is dormant.