The western red cedar (Thuja plicta) is also known as great western arborvitae, canoe cedar, Pacific red cedar, shinglewood, and giant red cedar. This evergreen can grow to a height of 50 to 60 feet with a spread of 15 to 20 feet. It is hardy from zone 5 through 9. It is generally used in landscape design as a hedge, screen or wind-break.
This evergreen requires very little pruning. The reasons you will prune are to remove damaged branches, sharing to maintain size, and for safety reasons (walkways, structures and roots).
Cut off any damaged branches as soon as possible. Be sure to make a clean-cut so that the tree will heal properly. (Note: Making a clean cut means after pruning the branch there should not be any ragged edges or torn bark at the site of the cut; as this creates an entryway for disease.) The tool that you use will depend upon the size and location of the branch.
Shear the Western red cedar in the early spring if you are using it as a hedge, screen or wind-break. (Light shearing will promote new growth and maintain its appearance.) You will use your hedge trimmers and cut away growth/needles to maintain the desired appearance of your hedge. This should not be done harshly, as you do not want to expose the deadwood at the center of the tree, you merely want to trim the hedge.
Visually check your tree to make sure that it is not interfering with walkways, rubbing against your home, or overhanging your roof. Branches rubbing on the roof can cause damage over time that may lead to a leaky roof.
Prune away or shear the branches that are a safety hazard. This will be a judgment call depending upon how close the branches or growth of the tree is to the walkway or structure. If it appears that just trimming them lightly with your hedge trimmers will solve the problem then shearing would work well. If a large portion is interfering and causing a safety problem then you will need to determine what branches need to be removed and lob them off with your lopping shears. In severe cases you may want to consider having the entire tree removed to solve the problem. This should be done in the early spring or late fall. Complete removal of the tree of course can be done at any time.