The most common conifer species you will find in a garden is Leylandii. These need to be trimmed once (or at most, twice a year). Some people recommend trimming it three times (or more!) a year but this isn’t necessary and, in fact, can weaken the Leylandii hedge especially in years of drought or during other forms of stress. Leylandii hedges that are trimmed too many times do not get a chance to put on any re-growth before the spring, so they are more likely to suffer from problems. Burning is a common problem where harsh pruning at the wrong time of year or under the wrong weather conditions causes them to burn or go brown.

Leylandii are extremely fast growing and can comfortably grow up to 3ft a year and quickly get to a height where more extensive pruning needs to be done. If you keep your hedge at a height of 6-8ft (2-3m), it is much easier to trim than if it is 10-15ft (4-5m) in height.