According to the University of Missouri, the black walnut tree is one of the most valuable hardwood trees grown in the Midwest for lumber. The walnut tree also produces edible nuts and is aesthetically pleasing. Trimming a black walnut tree can help it maintain its health and help produce knot-free boards and veneers at harvest time. This increases the value of the harvested lumber. However, the tree must be pruned correctly.
Wait until the tree is in its dormancy during the late winter and early spring months to prune it. This reduces the chances of infection.
Plan your pruning cuts out before pruning your tree. Never plan to remove more than 1/3 of the tree's total growth during a pruning session. This will damage the tree.
Remove any dead or diseased limbs, as well as branches that cross or rub.
Cut heavy limbs by making an initial cut to the underside of the limb that extends 1/3 of the way through the limb. This is known as a back cut. Remove the limb in its entirety by sawing completely through the limb from the top side at a point a few inches further down the branch from the tree. This will prevent the limb from stripping bark from the tree when it is cut down.
Smaller limbs and stubs should be removed with a cut that runs from a 45 degree angle away from the tree. This cut should be made outside of the ridge of growth, which is known as the branch collar, that grows in the forking region between the tree and limb.