The best time of year to reroot a tree branch depends on the type of tree and the method you are using. In general, hardwood cuttings are taken during the dormant season, which is usually in late winter or early spring. Softwood cuttings, on the other hand, are taken during the active growing season, typically in late spring or early summer. It's important to research the specific tree species you are working with to determine the optimal time for rerooting. By following the appropriate timing, you can increase the chances of success in establishing roots and promoting healthy growth.