When to trim hedges

New hedges require formative pruning for their first couple of years after planting. Formative pruning is usually carried out in winter or early spring.

After this, maintenance trimming is carried out, usually once a year for informal hedges and twice a year for formal hedges. Some formal hedges may need three cuts a year. Maintenance trimming is generally carried out between spring and summer. Timing of pruning should take into account the potential for nesting birds (see 'Problems' section below) and be delayed until after the nesting season - considered to run from March to August - if there are any signs that indicate activity.

See our advice in hedges: pruning times for more detailed information on timing.

Trimming techniques

Hand-held hedge shears are fine for smaller hedges, but for large hedges you'll probably find it easier to use an electric or petrol hedge trimmer. No matter what you use always make sure the equipment is sharp and well lubricated.

Always think of your safety when using a powered hedge trimmer. Wear safety goggles and sturdy gloves. Before starting, remove any obstacles on the ground. Avoid using powered tools above shoulder height and use sturdy step ladders or platforms, ensuring they are stable. Electric hedge trimmers are ideally used with a residual current device (RCD) and should not be used in damp conditions. Place the cable over your shoulder to prevent it being accidentally cut. See our advice in electricity in the garden for more safety tips.

Formal hedges

There is no need for the width of even vigorous hedges to exceed 60cm (2ft) if they are regularly trimmed. Formal hedges should be slightly tapered on both sides so that the base is wider than the top and light can reach the bottom of the hedge. This is known as cutting the hedge to a batter.

Follow these tips to ensure an even, symmetrical hedge:

• Cutting straight, crisp edges by eye can be difficult. Use a taut horizontal string tied between two stout canes to act as a guide to cut the top of the hedge level. Canes or stakes pushed into the ground help with vertical lines
• To shape the top of the hedge (e.g. to an arch), cut a template of the shape required from cardboard or plywood. Place the template on the hedge and cut following the line of the template, moving it along as you proceed
• When using shears, ensure that the top of the hedge is cut level and flat by keeping the blades of the shears parallel to the line of the hedge
• When using a hedge trimmer, keep the blade parallel to the hedge and use a wide, sweeping action working from the bottom of the hedge upwards, so that the cut foliage falls away

Informal hedges

Pruning an informal hedge is much like pruning normal shrubs. See the links below for more specific information on pruning shrubs;

Shrubs: pruning evergreens
Shrubs: pruning summer-flowering
Shrubs: pruning early-flowering

In general, when pruning informal hedges, remove misplaced shoots and cut back the hedge to its required size. Use secateurs or loppers where practical, especially if the hedge has large evergreen leaves, to avoid unsightly leaf damage.

How to trim hedges

Hedges can be divided into three groups:

Group 1 - Upright plants

For example: deciduous (hawthorn, privet); evergreen (box, Escallonia, Lonicera nitida)

Formative pruning

Deciduous:

• Cut back plants to 15-30cm (6in-1ft) on planting
• In summer, trim side branches lightly to encourage bushing out
• In the second year (February to March) cut back growth by half
• Throughout the second summer, trim side branches to maintain sides that taper towards the top
• In the second autumn, cut the topmost branch (‘leading shoot’) to the desired hedge height

Evergreen:

• Cut back all stems by one-third after planting
• Repeat this at the same time next year

Maintenance trimming

Annually, during May to September, trim back the top and sides every four to six weeks to maintain the desired shape.

Group 2 – Stocky deciduous plants, naturally bushy at the base

For example: beech, hornbeam, hazel, Forsythia and Ribes sanguineum

Formative pruning

• On planting, cut back leading shoots and side shoots by one-third, cutting to a well-placed bud
• Repeat this in the second winter to prevent straggly growth and thicken up the hedge base

Maintenance trimming

Trim annually in June (or after flowering) and again in August; clip to a shape that tapers at the top.

Group 3 - Conifers and most evergreens

For example: Lawson cypress, Leyland cypress, yew, bay, cherry laurel, cotoneaster and pyracantha

Formative pruning

• On planting, leave the leading shoot unpruned, lightly cutting back any straggly side shoots
• In summer, trim sideshoots and tie in the leader to a supporting cane as it grows
• Use secateurs for broad-leaved evergreens (e.g. laurel and bay)

Maintenance trimming

Clip to the desired shape one to three times during summer, until late August (yew can be clipped into September), when trimming should cease to reduce the risk of bare patches (see problems below). Use secateurs or hand shears for broad-leaved evergreens (e.g. laurel and bay). Stop the leading shoot at the desired height. Most conifers will not re-grow from old wood, so avoid hard pruning.

Informal and flowering hedges

Prune informal hedges where flowers are desired only once at the correct time of year to encourage flowering the following year. Pruning at the wrong time of year could remove the growth that will flower next year.

Prune those plants that flower on the current season's growth (e.g. Fuchsia) once in spring, as they will still be able to produce flowers that year.

Reduce the current season's growth by half in summer for plants that flower on one-year-old growth (e.g. Pittosporum).

In the case of shrubs that produce berries, such as Cotoneaster and Pyracantha, delay trimming until the berries disappear.

Problems

When undertaking work on garden hedges check that there are no birds nesting, 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. Stop work immediately if you suspect birds are active. The job can be delayed until after the end of August if necessary.

With conifer hedges, make sure you do not trim them after August, as this can encourage bare patches to develop in the hedge. Yew can be safely pruned into early autumn (Sep). Some gardeners have reported skin irritations after handling Thuja (western red cedar) trimmings so it is advisable to wear long sleeves in addition to gloves and goggles when pruning Thuja hedges. For guidance on other plants which may cause irritation, see our advice page on potentially harmful garden plants.

Boundary hedges can quickly grow to overhang the street or pavement. These should be trimmed to ensure they do not impede access by pedestrians. Even regularly trimmed hedges can gradually get bigger over the years; most deciduous and broadleaved evergreen hedges can be successfully renovated but some (including many conifer hedges) are best replaced when overgrown. See our page on nuisance and overgrown hedges.