Pruning is an important element in caring for coniferous trees such as firs. Many fir trees are weakened or killed because of improper pruning. Pruning a fir tree should be undertaken with a focus on training a tree into a proper shape and removing unwanted growth. You should never sheer a fir tree so that the tree forms an unnatural, uniform cone shape.
Prune fir trees in late winter or early spring to minimize damage that can weaken the tree and lead to fungal infection during other seasons.
Prune fir tree limbs that are larger than a pencil with a hand saw and smaller limbs with pruning shears. Sharpen the tools by drawing a whetstone along the blades before pruning. Using sharp blades allows for the most effective cuts. Prune limbs that are up to 20 feet from the ground with a pole saw.
Mix a solution of 1 part bleach and 9 parts water. Saturate a cloth with this solution and wipe the pruning blades to sterilize them. Clean the blades immediately after removing diseased limbs and in between pruning individual trees to prevent the spread of disease.
Train young fir trees after they are planted to reduce growth problems. Focus the initial pruning on removing limbs that form weak angles off of the central leader, which does not split. Pinch off these limbs with pruning shears. Make a cut that slopes away from the tree at a 45 degree angle, starting outside the growth ridge where the branch meets the tree and moving away as the cut angles downward.
Locate the dead zone within your plant. The dead zone of a fir is located along the interior of each branch. This is an area where new shoots will not grow. The extent of your fir tree pruning is limited by the extent of the dead zone.
Examine the live zone of your fir tree for limbs that are dead, broken or diseased. Cut these limbs back to the closest healthy bud by making a cut straight across the limb just above the point that the bud emerges. If you cannot cut the limb back to a healthy bud, you must remove the entire branch back to the point where it emerges from the trunk of the tree.
Remove lower limbs from a tree if you wish to expose the lower trunk of the tree. To remove heavy limbs, saw through the bottom of the limb 1/3 of the way with a hand saw at a point 3 inches away from where the limb joins the trunk. Then saw completely through the tree's limb from the top downward at a point 4 inches beyond where the branch meets the trunk. Remove the stub left behind by making a 45 degree angled cut starting just outside the growth ring where the branch meets the trunk and sawing downward and outward.