The English walnut tree has two claims to fame: It produces an edible nut, and it serves as a good shade tree. The tree is easy to grow because it is adapted to many environmental conditions and types of soil. Because it quickly grows to its mature 60-foot height, it's wise to begin pruning it to a shape you desire while it is small. Pruning this tree can also benefit its overall health.
Examine your tree from a distance and determine what shape you'd like it to take. If you prune to the tree's natural spherical growth, it will respond better and mean less work for you in the future than if you try to force it into a topiary.
Cut lower branches back to the main trunk to encourage a strong trunk and open up the area under the tree so you can walk, mow or sit beneath it.
Open up the crown, or growing region at the top of the tree, by cutting branches near the top. Focus on smaller, narrow branches and leave healthy, larger branches. If you want to cut these larger branches back partway to maintain a spherical shape, this is an acceptable practice.
Prune any dead, dying or diseased branches every winter after the tree has dropped all of its leaves. At this time, you can also prune branches to maintain the tree's spherical shape.