Fir trees require very little pruning since they naturally grow in a cone shape. Plant your fir tree in a location that allows for this growth, as it is healthier for the tree and less work for you. Perform any mild pruning in late winter, before new growth emerges. However, removal of a dead or broken branch can happen at anytime throughout the year. Never top a fir tree. This causes multiple leaders to form and gives the fir tree a grotesque, rounded appearance.
Remove dead or broken branches first. Use three cuts if the branch's diameter is greater than 2 inches. Place the pruning saw underneath the branch about a foot from the fir tree's trunk. Cut up a third of the way through the branch. Make the second cut three inches past the first cut. This time, cut down one-third of the way through the branch. Make the third cut all the way through the branch just in front of the branch's collar.
Trim off any branches competing with the central leader. The leader is the fir tree's highest branch. Having more than one leader causes the fir tree to become misshapen. Cut the leader with pruning shears so it is 8 to 12 inches long. Cut the surrounding branches so they are 4 to 6 inches lower than the leader.
Cut back branches that extend past the tree's natural cone shape. Do not cut off more than 6 inches or the branch grows rapidly and weakens. Light annual pruning develops thick and strong branches.
Always ensure there is a growth bud behind your cut. Fir trees have a dead zone in the centre. If a branch is cut back to the dead zone, it is unable to grow more needles and must be removed.