Short answer
Leylandii (Leyland cypress) needs 2-3 trims in the growing season, according to the RHS. Cut little and often, always into green growth, because leylandii will not regrow from bare brown wood.
Leylandii grows very fast and can easily outgrow a garden. The most common mistakes are cutting too late and too hard.
Timing
- Late spring: first trim once growth is under way.
- Mid to late summer: second trim.
- Early autumn: optional final trim. Avoid trimming in hard frost or very hot weather.
The golden rule: stay in the green
Do not cut back into the brown, leafless centre. Conifers such as leylandii generally do not regrow from old wood, and the RHS advises replacing a badly overgrown conifer hedge rather than trying to renovate it. Trim regularly, taking off a small amount each time, and keep the top narrower than the base.
Working on tall leylandii
Tall hedges raise safety issues: use stable platforms rather than leaning ladders, and consider a pole trimmer for reach. Check our long reach trimmers and trimmers for large hedges. If a neighbour’s evergreen hedge is the problem, read high hedges law.
Whatever the species, check the hedge for active nests before you start. It is an offence to intentionally damage or destroy a wild bird’s nest that is in use or being built; see our nesting season guide.