Evergreen cedar shrubs and trees are popular and low-maintenance plants for hedging for either privacy or landscape definition. Cedar foliage is considered a narrow gauge evergreen and responds well the shallow surface shearing and shaping required to maintain formal hedging. It can also be allowed to grow in its natural form, untrimmed, save the removal of damage, for a more casual, unstructured hedging style. To prevent deep cuts into the body of the cedar, which can be difficult to regenerate, Texas A&M University recommends shallow pruning frequently--once per year or more often, certainly before excess growth reaches 1 foot.
Trim your cedar hedges in the spring after the last frost is passed, such as early April in warmer Southern climes and May or very early June in cooler, Northern climes. Pruning in these windows will minimize stress on the cedar plants.
Remove dead, damaged, discolored or broken foliage carefully and conservatively, removing just the tips of the affected branches if possible. Cut back to a point of healthy wood just above a leaf node or bud to encourage branching to fill in the hole left from pruning. Use secateurs for this fine, branch-by-branch grooming.
Train your cedar shrubs into formal hedging in the third year after planting with regular pruning sessions. Create the shape you desire, ensuring that the hedge is wider at the base and narrower near the top to encourage needed sunlight to reach the lower branches. Once lower branches become defoliated from lack of sun, they will not recover, and you will have an unattractive, top-heavy or lollipop look to your cedar hedge.
Maintain formal hedging with flat or curved tops and sides by using long-blade scissors shears or a long-blade mechanical trimmer. Hold the cutting blade roughly parallel with the cedar surface for flat planes of hedging and at a slight angle for curved planes.