Many hedges respond well to renovation, including beech, box, hawthorn, holly, hornbeam, Lonicera nitida and yew. These can all be reduced by as much as 50 percent in height and width in a single cut. More drastic renovation should be carried out gradually.

Most conifers (apart from yew) do not respond well to renovation, as they do not re-shoot from old wood. Conifer hedges require regular light trimming. If they have become overgrown, then a method for partial renovation is given below.

Deciduous hedges should be renovated in midwinter, when they are dormant and leafless.

Evergreen hedges should be renovated in mid-spring, as they respond better to pruning when in active growth and the risk of frost has passed.

Before undertaking work on hedges, check that there are no nesting birds in the hedge, as it is an offence under the Wildlife & Countryside Act 1981 to damage or destroy the nest of any wild bird while it is in use or being built.

Where drastic renovation is necessary (i.e. more than 50 percent reduction in height or width), it is better to stage this gradually over two or three years.

Year 1

• Cut back the width on one side of the hedge only
• Cut to at least 15cm (6in) less than the desired width, or almost to the main stems if necessary
• Remember to cut the hedge to a 'batter' (sloping sides), so it tapers from the bottom to a thinner top, allowing light to reach the bottom of the hedge
• Trim the other side of the hedge as usual
• Leave the height unaltered
• Mulch and feed in spring to encourage vigorous re-growth
• Allow a full growing season for recovery
• Water well in dry spells in the first growing season following renovation

Year 2

• Cut back the other side of the hedge, cutting almost to the main stems, if necessary. Cut to a similar batter as the previous side
• Leave the height unaltered
• Mulch and feed in spring to encourage vigorous re-growth
• Allow a full growing season for recovery
• Water well in dry spells in the first growing season following renovation

Year 3

• Cut back the height of the hedge to at least 15cm (6in) below the desired height
• Cut back harder where the upper portions of the hedge are open and patchy 
• Mulch and feed in spring to encourage vigorous re-growth
• Allow a full growing season for recovery
• Water well in dry spells in the first growing season following renovation

Hedge laying

Where hedge growth is good but thinning near the base, the process of “laying” can rejuvenate a hedge by encouraging new growth. Hawthorn is the best species for laying but most common deciduous hedge shrubs such as ash, blackthorn, elm, field maple and hazel are also suitable. Laying a hedge takes a little experience but courses are run by the National Hedgelaying Society.

Hedge laying should be carried out during winter, and is usually done on the ditch side of the hedge.

• Allow the hedge to grow to about 2.5-5m (8-16ft) in height, with main stems 5-10cm (2-4in) thick at the base
• Remove stems that are larger than about 20cm (8in), awkwardly-shaped or out of line
• Cut away side growth from the lower stems, and clear debris from the bottom of the hedge
• Cut almost through the main upright stems (known as pleachers) near the ground on the opposite side of the face to the direction you are planning to lay, and push them over at an angle of approximately 35° in the direction of the rising slope
• Drive stakes of hazel or ash into the hedge line every 40cm (16in) and weave the pleachers between these
• Twist binders or heathers of coppiced hazel, sweet chestnut or willow around the top of the stakes to secure the pleachers
• Trim the cut stubs of the pleachers to prevent the stools from rotting

Any unwanted pleachers cut from the hedge can be used to fill the gap at the end of the laid hedge.

These cannot be renovated in the same way as deciduous and evergreen hedges. Most conifers (with the exception of yew) will not re-shoot from old wood.

Examples of conifer hedges intolerant of hard pruning include Cupressus, Chamaecyparis and × Cuprocyparis leylandii (Leyland cypress).

When a conifer hedge has become too large, there are some steps that you can take to reduce its impact without complete renovation:

• Reduce the height by up to one-third in April
• Thin out the side branches, removing selected branches right back to the trunk but leaving the others intact. This will allow more light and air into the area around the hedge
• Mulch and feed in spring to encourage vigorous re-growth
• Allow at least a full growing season for recovery
• Water well in dry spells in the first growing season following renovation

Hedges reduced in height by more than one-third may not fill out, remaining flat and bare at the top.

Renovation pruning inevitably results in ugly bare patches, but re-growth should be sufficiently rapid to hide these within one or two growing seasons.

Where holes or bare patches have developed in conifer hedges intolerant of renovation, it may be possible to tie in a new branch to that bare area in order to cover it.

Brown patches can be a problem in some species of conifer hedge for one or more reasons. Environmental factors, pruning at an inappropriate time of year, aphids or fungal diseases may be to blame.

When reducing the height of a long hedge, it can be difficult to get a straight line along the top. Painting an indicator line of whitewash along the hedge just above the point of cutting may help. Alternatively, set up a string line along the hedge to act as a cutting guide.

If recovery seems poor after the first or second stage of renovation, delay the next stage for a further year to give the hedge time to re-shoot.