Fir trees naturally grow in a cone shape. They have one main trunk which larger branches grow out from. Topping a fir tree entails removing the main, large branches near the tree's top. This is not recommended since it weakens the branch structure and opens the tree up to disease. One reason topping is required is when the tree begins growing into power lines. To prevent this, plant all fir trees in open areas.
Select the branches to remove. Topping a tree means to remove the large branches from the fir tree's top portion. This invigorates growth in an upward pattern. The vigorous growth competes with the main trunk, causing the fir tree to take on a rounded appearance.
Use a pruning saw to make a cut halfway through the first large branch, from the bottom up, approximately 12 inches away from the tree's trunk. Move 2 inches further away from the trunk and make a second cut, from the top down, halfway through the same branch. Remove the branch right in front of the thick branch collar. Do not cut the branch collar or new growth may not occur.
Work around the tree removing the rest of the large branches. When you are done, the fir tree has its large branches on the bottom two-thirds. The top third of the tree looks like a stripped trunk. New growth will emerge at the top and grow up rapidly.
Most professional tree trimmers will not top a fir tree.
Topping a fir tree causes the tree's lifespan to decrease. It also makes the tree more susceptible to insect infestation and disease.