Hedges – when and how to cut

Establishing a good hedge begins with planting the right variety for your needs. The next step is to create a good framework. Finally, trimming the right amount at the right time will maintain your lovely dense hedge.

Bear in mind the rate of growth when choosing your hedging variety. Vigorous growers will provide fast results, but will then need more cutting back. Likewise, formal hedges require more frequent trimming than informal. Whatever type of hedge you have, it will need trimming at least once a year.

Electric/petrol hedge trimmers can be used for plants with small leaves, but you may want to stick with hand shears for plants with broad leaves (eg Cherry laurel, Portugal laurel), to avoid slicing straight through these.

Always cut in dry weather. This helps to avoid the spread of pathogens and is safer if you are using electric equipment.

Formative pruning

After you plant a new hedge, carry out formative pruning to guide the shape of your hedge. This usually amounts to only cutting laterals (sideways branching) until the desired height of hedge is achieved. New deciduous hedges, including native mixed, hornbeam and beech, should be pruned in winter; new evergreen hedges in spring.

Maintenance pruning – formal hedges

Formal hedges are the tidily clipped boundary type, comprised of a single species, for example beech, hornbeam, Thuja, privet etc.

On formal hedges, create a shape that is slightly narrower at the top. This allows light to reach the bottom of the hedge and reduces the chance of snow damage. A depth of up to 60cm is usually enough for a formal hedge. Formal hedges usually need cutting twice a year to maintain this depth.

For straight lines, use a string tied between two canes to guide cutting. Alternatively, you can use a template cut out of cardboard to help create the right shape.

• Cut deciduous hedges once in winter and once in midsummer
  
• Cut evergreen hedges in late spring and late summer
  
• Cut yew only once, in summer

Maintenance pruning – informal hedges

As the name suggests, an informal hedge is allowed to grow with more freedom than a formal hedge, displaying its natural growing habit. Escallonia, Pyracantha, dogwood and hazel might be grown in this way.

Once the right height has been reached, informal hedges can be pruned as shrubs – the timing based on their flowering. This need only be done once a year to keep its size, unless it is particularly vigorous.

Renovation pruning

Overgrown broadleaf hedges (e.g. beech, cherry laurel, hawthorn, hornbeam, holly) will generally respond well to hard pruning if they become neglected. Do this is mid-winter for deciduous hedges and in spring for evergreens. If you are making drastic changes, feed and mulch in the spring, then cut one side the following winter. Wait a year to repeat this on the other side, so as to minimise stress to the plants. Cutting the top should be done in a different year, as well. Decide on the size you would like the hedge to be, and cut back to 15cm (6 inches) less than this, each time.

Although hard-trimmed hedges will look quite bare are first, they will recover, especially if given feed and mulch. With a few exceptions, however, conifers do not regenerate from old wood. Therefore regular trimming in spring and summer is important to maintain a sensible size. This applies to:

• Chamaecyparis (eg Lawson’s cypress)
  
• Cupressus (eg Leyland and Monterey cypress)
  
• Thuja (Arbovitae).

Conifers that will take pruning into old wood are:

• Cryptomeria japonica (Japanese Red Cedar)
  
• Taxus baccata (yew).

Light foliage pruning should be done in spring and summer, but avoid particularly hot and dry weather. Try to leave at least 10cm (4”) of green foliage. Remove any debris left on the hedge to avoid this encouraging fungal disease.

Any heavy pruning, on broadleaves or conifers, should be done in autumn and winter, because resinous conifers bleed when cut, especially in spring and summer.

Dealing with holes in conifers

Brown patches sometimes appear on conifers. These can be cut out and growth will usually sprout from adjacent shoots to fill the gap. If a large bare patch results from removing dead foliage, then this can be disguised by inserting a cane into the gap, onto which you can tie other green branches. These will, in time, grow and cover up the hole.

Leylandii and the Law

The infamous Leyland cypress is the fastest growing conifer in the UK. With this in mind, think carefully about the height and depth you want to keep your Leylandii. If they are allowed to grow tall, then they are more difficult to trim and may need specialists to deal with them. They do NOT take cutting back into old wood – this leaves unsightly bare branches and brown foliage on show. A tidy Leyland hedge needs regular maintenance.

Under the Anti-Social Behaviour Act (2003), you must not allow your hedge to spoil your neighbour’s reasonable enjoyment of their property. Likewise, you are responsible for any damage caused by an overgrown hedge.