Topping Off and Pruning Arborvitae

Topping Off and Pruning Arborvitae

Evergreen arborvitae (Thuja) shrubs and trees are members of the Cypress family members and thrive in U.S. Department of Agriculture plant hardiness zones 3 through 9. Even though these refined and elastic trees maintain their normal contour as they mature, regular pruning maximizes their longevity and improves their overall look. Arborvitaes create an abundance of vertical limbs which have a tendency to shade lower branches. Pruning allows air and sunlight to penetrate all parts of the trees. The best time to prune arborvitaes is in early spring before new growth appears. Topping arborvitaes, however, affects the trees’ growth.

Selecting and Cleaning Applications

Without proper pruning tools, a simple pruning job can quickly turn to disaster. Clean pruning cuts are crucial to maintain the integrity of plant tissue. Torn or crushed flesh invites diseases and insects. The best pruning tools are manufactured of tempered steel and have a sharp edge. Pruning tools must be the correct size for the job. Hand pruners are best for cutting branches that are far less than 1/2 inch in diameter while lopping shears should be used for branches which are between 1/2 and 1 inch in thickness. If branches are larger than 1 inch thick, a pruning or bow saw is the best tool. Ideally, pruning tools must be cleaned after every cut is made. Following that procedure helps to protect against the spread of disease. If cleaning tools after each cut is too onerous, clean them before and after each pruning occupation. The best way to sanitize a tool is to dip its sharp edge in a solution of 1 part bleach and 9 parts water. Apply a thin layer of petroleum to every tool blade once you finish pruning to keep every single blade from rusting.


Arborvitaes are narrow-leafed evergreens with random branches which respond best to selective thinning cuts instead of complete shearing. Thinning cuts eliminate branches for the point of origin. Upper branches which shade lower branches must be thinned to permit sunlight to reach the lower branches. Do not ever trim a branch back to bare wood because it won’t create new growth; growth happens at the branch tip. Although thinning individual branches back to an upward growing side branch is time-consuming, it is worth the attempt.

Removing Diseased, Dead and Damaged Wood

Even though arborvitae trees are not susceptible to diseases, it is imperative to eliminate their diseased timber immediately after it is found. Cut diseased branches back to the main trunk, and dispose of them immediately. Branches which are dead or were damaged from heavy snow or other extreme weather have to be eliminated in exactly the exact same manner.


Topping is often done when a tree height becomes problematic. When the very top of the arborvitae is cut off; however, it leaves a very flat and unsightly leader. No new growth will happen once the upwards growing branch tips have been cut. No proven horticultural benefit is for topping an arborvitae. The only time that topping may be beneficial is in an emergency once the very top of the arborvitae tree has been damaged.

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