The easiest way to trim an established conifer hedge such as Thuja plicata is by using a powered hedge-trimmer to give a regular, even finish. Quick-growing conifers will need about three cuts per year during the growing season, at roughly eight week intervals.
Inspect your hedge thoroughly before trimming it to ensure there are no birds nesting within. It’s an offence under the Wildlife and Countryside Act 1981 to damage or destroy the nest of any wild bird while it is in use or being built.
Here’s how to prune a conifer hedge.
You Will Need
Hedgetrimmers or hand shears
Use long bamboo canes to mark the top edge along one side of the hedge. Push the canes down into the hedge.
Pushing canes into the hedge
Tie strong string between the canes to mark a straight edge as a guide to cut to. Check the string line is taut.
Tying string between the canes
Trim the top of the hedge by holding the hedge-trimmer horizontally with both hands and using the string line as a guide. Wear protective goggles and gloves and make sure you have a firm footing on a ladder or a platform for tall hedges.
Trimming the hedge horizontally
Clip the sides of the hedge using the string as a guide. Hold the hedge-trimmer vertically and make long sweeping strokes to ensure an even finish.
Trimming the side of the hedge
Remove the canes and string line before using the hedge-trimmer to tidy up the top edges. Hold the cutting bar at a 45-degree angle.
Tidying up the hedge edges
Test any ladders and platforms to make sure they are stable before getting on them with a hedge-trimmer. Make them more secure by tying them in to the hedge with a strong rope.