A dense hedge requires regular pruning to maintain shape, size and health. Trimming this type of screening plant involves more than simply breaking out the hedge clippers for a flat haircut. Hedge plants require thinning in the interior of the plant to increase light to promote new growth. Learning the best way to trim hedges requires selecting branches for trimming as well as shaping the plant into a pleasing privacy screen.
Schedule pruning for immediately after the plant finishes flowering for the season. The best scenario allows thinning and hedge trimming in late spring to early summer to allow the plant time to rejuvenate before the onset of cold weather.
Select the correct pruning tool for your work. Pruning clippers trim branches up to 1/2 inch thick. Pruning loppers tackle branches up to 2 inches in diameter. Use the pruning saw for larger branches or those in hard to reach locations.
Prune damaged or dying branches back to the trunk or the closest healthy branch. Angle cuts to try to minimize the chance of leaving a nub at the pruning site. Pruning stimulates new branch growth at the point of the cut so place each cut where you want the plant to flesh out with foliage. Placement of pruning cuts close to the nearest green bud induces the plant to branch outward in that direction.
Focus on removing excess foliage to allow light into the interior of the hedge. Begin selecting and clipping the oldest branches to thin the shrub. Make cuts flush with connecting branches and the trunk using the correct tool for each sized branch. Do not hack through a branch with a dull pruning tool. Open, ragged wounds invite pests and disease into the plant.
Thin the entire plant to open up the interior to light and new growth. Pay particular attention to the overall shape of the hedge. Gardeners often clip hedges for density at the top of the shrub. Focus thinning activities down to the soil level to induce full foliage at the bottom of the plant.
Use hedging shears or motorized hedge clippers to shape the plant. Work from bottom to top to properly shape the plant by removing a few inches of branches at a time. Use a level motion with the clippers. The final hedge should have a slightly wider bottom than the top portion of the plant. A gradual angle to the hedge top also fights against the crushing weight of snow and ice in winter.
Dispose of all trimming in recycling yard waste bags or in the compost pile. Some hedges self-sow from clippings left in the hedge garden.