How to Trim a Canadian Hemlock

Determine the height you want the hemlock to be. If it is on either end of the house, 6 to 8 feet tall frames the average size house nicely. If it is near any windows, a hemlock tree is not a good choice for a foundation plant because keeping it trimmed to an appropriate size is not practical. If you have one of the dwarf shrub cultivars of hemlock, however, they are excellent anywhere along the foundation line.

Shear the ends of the branches with a hedge trimmer -- manual or power -- following a pyramidal or oval shape to suit your preference. Make sure it is balanced and even around all sides. It is preferable to do this step every year taking out the least amount of material needed, but hemlocks are very forgiving and if you do let it go too long, you can cut off as much as you need.

Create a more natural appearance by using hand pruners. You still need to control the height, form a shape and have symmetry and balance, but hand pruners result in a more informal look. You can take off as much material as you want, as there are new grow points all along the stem. Be consistent, but not exact, around the whole plant.

Leave the leader unpruned if you are growing hemlock as a specimen plant in an open area and do not have any height restrictions. The leader is the central stem of the tree and is responsible for the ultimate height of the tree. If you must reduce the height of the plant and prune the leader, train another branch to become the leader. To create a denser plant, trim the ends of the branches 6 to 12 inches as needed. Do not trim all the branches the same amount. Follow the natural form and maintain a pyramidal form. If you want a less dense appearance, you can thin out some branches to open up the canopy. Follow a branch all the way back to where it originates and cut it off.