Pruning is best done during the dormant season to invigorate the tree. This is the best time to prune out diseased wood, crossing limbs, or narrow crotch angles. Pruning during the summer can control vigorous shoot growth.
To prune mature trees, cut out dead wood, thin out crowded or crossing branches, and remove limbs that are lower than desired. Moderately thin out the small fruiting wood throughout the tree by making small cuts in limbs about 1 inch in diameter.
The natural appearance of the walnut tree is best maintained by making only thinning cuts--cuts close to and parallel with the parent limbs or next to a lateral limb. Do not leave any branch stubs. Do not cut branches that are larger than 4 inches in diameter because large wounds are slow to close and may be an entrance point for fungi.
