Hemlocks are large, graceful trees known for their pyramid-like shape and drooping branches. The tree has delicate leaves that are dark green on top and silvery shite underneath. Several hemlock species are native to the United States -- the western hemlock (Tsuga heterophylla) is found in much of the Pacific Northwest, and the Eastern hemlock (Tsuga canadensis) is native to the eastern half of the country. It is preferable to let hemlock trees grow in their natural form, but the species responds well to shearing and heavy pruning. The purpose of pruning is to remove dead and diseased wood, shape the tree and improve its health.
Prune hemlock trees in late winter or early spring, right before growth begins. This will result in the least amount of damage to the tree.
Cut branches that have less than 60-degree angles to the main trunk of another branch. They are weaker and are less likely to survive.
Remove diseased, dead and broken wood any time of the year. Cut the unwanted branches off at their base, where they meet healthy wood. Place the cut on the healthy wood to avoid spreading disease.
Trim limbs clogging up the center of the tree by crossing or rubbing against each other. Cut off the limbs at side shoots. This will free up space for sunlight and air to circulate.
Shear hemlock trees for a more formal shape. Run hedge clippers along the sides of the tree, removing a little of the foliage at a time. Keep shearing until you achieve the desired shape. This will promote more branches to grow from the trunk, filling in any bare spots.