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Hedges can quickly become overgrown, filling up a border and becoming difficult to maintain. Renovation may rejuvenate an old hedge. With legislation in place concerning the height of evergreen hedges, renovation may be advisable where hedges have got out of hand.
Hedge Renovation. Credit: RHS/John Trenholm
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.
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.
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:
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.
Hedges: nuisance and overgrownHedges: plantingHedges: pruning timesHedges: trimmingHedges: selectionHigh hedges
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