Black walnut trees are ideal on landscapes or in gardens because they create a spread with shade, help to eliminate greenhouse emissions and can be harvested for wood and nuts. They can live for more than 200 years, so they are great investments. Trimming and pruning the tree is necessary to a black walnut's health and maintenance. There are some key things to keep in mind when trimming black walnut trees.
Prune only those trees that are at least 6 inches in diameter around the trunk and whose branches are at least 2 inches in diameter. This will reduce chance of disease.
Trim black walnut trees during their dormant period so they can heal before the growing season. Do not cut into the collar of the tree to ensure that no live tissue is damaged. Apply anti-fungal treatment to the open wound after each trim.
Tim the bottom growth of the black walnut tree first. Trim off any dead or broken branches using pruning scissors for branches no bigger then 2 inches in diameter, pruning shears for branches no larger then 5 inches in diameter and loppers for all other branches. Trim away any branches that are growing at awkward angles, such as into other branches or straight up or down.
Prune off any branches that are crowding out air circulation and light so sunlight can reach the trunk. Pick out the ones that appear the weakest or thinnest. Don't trim back more then 50 percent of the bottom growth and leave as much healthy growth as possible.
Trim the crown of the black walnut tree. Prune excessively long or heavy branches to give the tree a more balanced appearance. Trim branches that are broken, dead or that are smaller then 2 inches in diameter and growing at awkward angles. Don't trim off more then 25 percent of the crown.
Discard, burn or compost the black walnut tree branches and trimmings.