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Prune mature trees once every 3-5 years to preserve their shape. Cut off low or damaged branches to maintain the central leader shape. Remove any forked or crossing branches to keep your tree healthy.
When pruning young trees, you create the shape and structure of the tree for its entire life. Your later prunings are to maintain the structure and polish up the appearance of your tree. To do this, look for any new, fresh branches and cut them off with your garden shears. Just like you did when pruning your young trees, inspect your trees for branches below 45ft (1.21.5m), and look for any damaged branches or discolored areas. If you find any low-hanging or sickly branches, cut them off at a 45-degree angle near the trunk. This keeps your tree healthy as it continues to grow and produce walnuts. You can use your garden shears, as these branches shouldn't be very thick. As new branches grow, they may take a forked appearance or may start to grow across one another. If you notice any forked or crossed branches, cut them off using your garden shears or hand saw. Make your cut as close to the trunk of the tree as you can, and use a 45-degree angle as you cut. If you'd like, you can remove the smaller of the forked branches and keep the larger section. Do this if the branch is towards the top middle of the tree and if it looks attractive.