The Complete Guide to Tree Trimming and Pruning Techniques with Essential Tools You Need And Information on When to Cut, Prune, and Maintain Trees Proper tree trimming and pruning techniques are essential to the health of a tree. Tree care experts recommend that trees be trimmed or pruned at least once a year. There are three types of trimming: crown reduction, topiary, and shearing. Crown reduction is used to maintain the shape of the tree by removing branches that grow too