Renowned as the fastest growing walnut trees, English walnuts tolerate a variety of soils and develop a dense, deep-green canopy. This prolific producer grows as tall as 60 feet and provides plenty of shade. Ideally, pruning should commence when the tree is very young to encourage it to form its shape, and continue every three to five years to invigorate it, maintain its shape and improve its health and nut production. It also enhances the appearance, so it looks appealing against any landscape.
Prune the top third of the tree down to a dormant bud at the time of planting. This bud develops into the main shoot and creates a single leader or trunk. Allow this main leader to grow upward the first three years so it develops into a central trunk. Also select the strongest branches from the central leader to form scaffold (primary) branches, from which other branches eventually grow. Allow the central leader and scaffold branches to form for three years, thus giving the walnut tree its shape.
Examine the growing or mature English walnut tree, preferably from a distance, to decide its shape. The natural shape of the tree is spherical, which means the branches are lateral. Pruning to enhance its natural shape requires less maintenance as opposed to giving it an unnatural shape.
Cut low-lying branches back to the trunk with loppers to clear up the space underneath the tree used for sitting, walking or mowing easily. Use a pruning saw for branches thicker than 6 inches. Also remove dead or dying branches to encourage a strong framework.
Remove thin, narrow and smaller branches near the top of the tree to open the crown. Depending on personal taste and the desired shape you want to tree to have, leave the larger, healthier branches intact, or cut them partway to conform to the spherical shape.
Inspect the nodes, or the points where one branch meets another. Every spring new buds develop that grow into twigs and form a new node. Cut all visible nodes to thin the crown, so more sunlight and air penetrate the tree. Also remove branches with V-shaped joints as they are weaker and crack easier, compared to those with U-shaped joints.
Collect all clippings in a tarp and dispose.