It is tempting to ruthlessly prune an unsightly neglected hedge, but severe cutting can overstress the plants and recovery will be slow. Renovation pruning a particular hedge depends on two things, the type of overall effect you are trying to create and the individual requirements of the neglected plant. An overgrown dense, formal hedge will need a vigorous pruning but an informal flowering or fruiting hedge will need much less attention in order to achieve a desirable look.
Be patient. When renovating a neglected hedge, remember that the hedge is a living thing and will have to be retrained, which will take time.
Prune when the time is correct. It is important to prune neglected hedges at the time of year appropriate to the plant. Trim only one side hard to encourage new growth from the centre of the hedge. You may repeat this drastic pruning in the following year on the other side of the hedge while only lightly trimming the new growth on the other side.
Trim after blooms or fruit have fallen. Pruning should be done after the plants have flowered, but do check the needs of individual species before pruning. For example, berry hedges are generally left until the berries have finished fruiting or the birds have eaten them. As a rule, simply cut out any congested or weak areas, shorten old shoots and cut back some shoots almost to the ground in order to encourage basal shoots.
Decide which tools to use for cutting a hedge according to the area that needs trimming. Pruning shears will suffice for lightly trimming the occasional shoot and are adequate when quite small areas of hedge need trimming. Use power tools for large jobs. Power tools make light work of large expanses of neglected hedge. Always use the appropriate safety equipment when using power tools in the garden.
Make a height guide. A string line gives an accurate cutting guide for trimming a formal hedge. Fix a taut, brightly coloured line at the required finished height of the hedge as an easy-to-see guide.
Always wear protective gloves and eyewear when trimming hedges.