The hazelnut (Corylus avellana), also known as the filbert, is a shrub which is trained to grow as a small tree, reaching a height of 15 feet in maturity. Native to Europe and Asia, commercial hazelnut production in the U.S. is centered in Oregon and Washington. Annual pruning of the hazelnut tree protects it from winter breakage and helps to improve the tree's yield. Prune the tree from December through February. Use pruning shears for suckers and other spindly growth and a hand saw or lopping shears to cut thick branches.
Cut off all branches but three to five main scaffold branches during the hazelnut tree's first winter. Scaffold branches form the tree's framework and are the primary limbs of the tree from which all other branches will grow. Choose three to five strong, healthy branches, equally spaced around the tree. The bottom branches should be longer than the top branches, so that the tree is shaped like a triangle. Allow those to remain and cut off all other branches, back to the trunk.
Remove any branches that appear to be competing with the scaffolding branches the following year. Any branches that are growing thick should be taken off, back to their sources of origin, leaving only the scaffold branches you chose last year.
Prune out dead, dying and diseased wood annually. Cut off any branches that are crossing over others or that point down, toward the soil. Remove all branches back to the parent branch. Leaving stubs or cutting just a portion of the branch will cause a flush of growth directly below it that will shade the interior of the tree.
Remove suckers as they appear. Suckers are thin branches that grow from the soil at the base of the tree, or from the tree, below the graft union. Suckers can usually be removed by hand or with pruning shears. If you want your hazelnut tree to grow in bush form, allow the suckers to remain.