How to Prune the Top of Thuja Trees in a Temprate Climate

Prune your Thuja in the late winter or early spring before new shoots emerge. A second pruning in the summer or early fall can be executed to trim away any shoots that extend beyond the boundaries established by earlier pruning.

Shear the top of your Thuja to a more precise, but still natural, tapered point by holding the pruning shears roughly parallel with the side of the tree where you want the taper to begin. Increase the angle of the blades toward the tree as you move up toward the point of the tree. Work around the canopy top evenly to achieve a smooth cone shape.

Create a flat top or Greek column shape by shearing off the top of the Thuja in a straight level cut at the desired height. Hold the pruning shears perpendicular to the tree canopy and make flat, even cuts over the entire tree top. Achieve a perfectly level top by laying a long level across the diameter in several positions, trimming lightly as necessary until perfectly level. This can be especially useful when Thujas are planted adjacent to one another and must match up.

Collect all of the small, loose cuttings that will fall into the canopy and down to the soil. These can invite disease when they decay and will also turn brown, marring the even green appearance of the Thuja. If your tree is very large, give the trunk and few gentle shakes to help lodged cuttings fall through to the soil where they can be scooped up.