Maintenance Pruning. Once established, an informal privet hedge -- one where individual shrubs keep their natural shape -- is pruned after the plant's fragrant white flowers bloom in mid-spring. You should only need to prune informal hedges once a year, removing...
For many garderners, pruning privet hedges is less a chore, than a form of gentle therapy. The privet is one of the perfect plants for hedging. It has a history going back many hundreds of years and is (along with the buxus) the quintecentially British hedge.
First of all, they are poisonous plants. Secondly, not being evergreen in the North, privet hedges will be attractive for only a portion of the year there; for the same reason, they cannot furnish privacy year-round.
During the first two years, severe pruning allows the hedge to spread and become fuller at the base, so do not worry about the height of the privet hedge during the early years. After the hedge is established and healthy, allow it to grow to the desired height.