How to Prune an Arborvitae

Several well-trimmed arborvitae sit in a row against a building.
What You'll Need
Pruning tools
What You'll Need
Pruning tools

Many species of arborvitae do not require pruning and will naturally take on an attractive pyramid shape. However, if you wish to limit the height of the tree or shape it to a hedge or topiary, pruning is necessary. Pruning can also help stimulate new growth and allow more light to reach lower branches. Always refer to the care instructions that come with your tree, as these vary somewhat depending on the cultivar you have.

Step 1 - Choose the Proper Season

Prune arborvitae to reduce height in the late winter, before the sap rises in the main trunk. To thin out overgrowth, prune in mid-summer, so new growth can take hold before the tree goes dormant for winter. Prune down to ground level in the early spring, before flowering and budding. Ornamental pruning to reshape tall hedge rows into a moderate hedge can be done in the late spring, after flowering.

Step 2 - Prune at the Correct Location

For top-down pruning to reduce overall height, cut well above the junction of a branch and its shoots. This will prevent shoot and bud growth above the cut.

Tip: Always work around the tree rather than focusing in on one section, as this will help keep pruning even.

To thin out an arborvitae, cut close to the junction of new shoots with the main branch. This will encourage new growth vertically instead of outward and allow more sunlight into the center of the tree. Do not prune back beyond where you see green foliage.

Prune down to ground level by removing secondary branches and the leaders (the large limbs that fan out directly from the trunk). Remove these in 18-inch sections to avoid tearing the trunk's bark. Hire a professional arborist, trained in the use of electric and manual saws and in safe cutting techniques to do this task.

To reshape an arborvitae hedgerow, use a combination of top-down and thinning styles of pruning. Cut at a moderate 30-degree angle into all branches to prevent damage to bud junctions.

Tip: Step away from pruning often so that you can assess your work. It is hard to do this when you are right on top of the tree.

Step 3 - Clean Tools While Pruning

Check that your pruning shears are in good condition: sharp, clean, and smoothly operating. Dust and lightly oil your shears before starting a pruning job.

Tip: Dispose of all limbs and foliage. Do not leave them on the ground as they could spread disease and encourage pests.

After each cut, wipe all bark, sawdust, sap, and leaf residue off the blades of the pruning shears. When pruning healthy trees, disinfect the shears between each tree you trim to prevent spread of disease. Use a mild solution of Lysol, an antibacterial mouthwash such as Listerine, or rubbing alcohol. Pine-based cleaners and chlorine bleach have been shown to corrode yard tools, so these are best avoided.

When cutting dead or diseased limbs, cut into sound wood far below where the unsound limbs meet main branches. Prune carefully, with good-quality tools, sound advice, and good judgment. Careful pruning will extend the life and beauty of your arborvitae trees and maintain your privacy and comfort for generations.

Need the right pruning tools? Check out our Garden Tools Buyer's Guide.