Renovating Hedges
A number of hedging species respond well to renovation even if they have been neglected for some time. For example, holly (Ilex aquifolium), yew (Taxus baccata), laurel (Prunus laurocerasus) and beech (Fagus sylvatica) can be cut back hard into old wood, and they will still sprout. However, conifers such as Leyland cypress (x Cupressocyparis leylandii) are often more problematic, and may take a long time to recover their looks after hard pruning.
Renovation Tips
Renovations tend to be more successful when the hedge has been fed and mulched in the season before pruning, and then again after cutting back to encourage healthy new growth.
It is generally best to cut back one side of a neglected evergreen hedge in spring (winter for deciduous), then wait until the following season before attempting the other side. This will prevent the hedge from receiving too great a shock to the system.