Hedges that are well established will need to be trimmed to keep them compact and dense. If the hedge is a formal hedge, it will need trimming more frequently.

When is the best time to trim a hedge?

Newly planted hedges will need formative pruning during their first few years after they have been planted. This pruning usually takes place in early spring or winter. After formative pruning, hedge trimming for maintenance usually happens once a year if the hedge is an informal hedge or twice a year if it is a formal hedge. Some formal hedges are cut three times per year. Maintenance hedge trimming usually happens between the spring and the summer months. The timing of hedge pruning needs to take into account nesting birds and it should be resisted until the nesting season has finished if there are signs of nests in the hedge. Nesting season usually runs between March and August.

Hedge trimming techniques

For hedges that are relatively small, you can use hand-held shears. For larger hedges, it is a lot easier to use a petrol hedge trimmer or electric hedge trimmer. Whatever equipment you use to trim your hedge, make sure that it is well lubricated and sharp.

Whenever you used a powered hedge trimmer, always bear in mind your safety. You should wear PPE (personal protective equipment) like gloves and goggles. Before you begin, you should look on the ground for any obstacles or things you could catch with the trimmer. You shouldn’t use a power tool above the height of your shoulder and, if you use a step ladder or a platform, you need to make sure it is stable. You should never use an electrical hedge trimmer when it is damp and you should always use an RCD (Residual Current Device) while keeping the cable on top of your shoulder so that you don’t cut into it accidentally.

Formal hedge trimming

If formal hedges are regularly trimmed, they won’t need to exceed 2ft or 60cm. A formal hedge should have slight tapering on both of its sides making the top narrower than the base. This means that sunlight can reach the lower part of the hedge. This process is called ‘cutting to a batter’.

In order to ensure that your formal hedge is symmetrical and even, you should:

• Use a string that is tied horizontally between two canes as a guide to cutting the hedge at the top. Making a crisp and straight edge by eye alone is very tricky. For vertical lines, you can use a cane or stake in the ground.

• For shaping the hedge at the top (into an arch), you should cut a plywood or cardboard template to your required shape. You need to put the template onto the head and follow its line as you cut. You need to move it along the hedge as you go.

• Whenever you use shears, make sure the hedge is flat and level at the top by ensuring the shear’s blades are parallel along the hedge line.

• Whenever you use a hedge trimmer, make sure the blade is parallel to your hedge and keep your cutting actions wide and sweeping. Always work from the bottom of the hedge towards the top to ensure that all of the foliage will fall away.

Informal hedge cutting

Informal hedge pruning is similar to pruning shrubs. Generally speaking, informal hedge pruning means removing shoots that are misplaced and cutting back the hedge to the size you require. Where practical, use loppers or secateurs. This is important if the hedge is an evergreen with large leaves as it will help you to avoid leaf damage that is unsightly.

How to trim a hedge

There are three groups of hedges:

1. upright plants – evergreens (box, Lonicera nitida, Escallonia) and deciduous (privet, hawthorn).

2. Stocky deciduous hedges whose bases are naturally bushy (Ribes sanguineum, Forsythia, hazel, hornbeam and beech)

3. Most evergreens and conifers (Leyland cypress, Lawson cypress, bay, yew, cherry, cotoneaster, laurel, pyracantha)

Group 1 pruning

Deciduous

• On planting, cut back the plants to 6in-1ft (15 to 30 cm).

• In summer, give the side branches a light trim to encourage them to bush out.

• In the hedge’s second year (between February and March), cut back the growth by half.

• During the hedge’s second summer, trim the side branches so that the sides taper to the top.

• During the hedge’s second autumn, cut the leading shoot (the topmost branch) to your desired height.

Evergreen

• ¬After planting, cut all of the stems to one third.

• Repeat this action at the same time the following year.

• For maintenance trimming, you should trim the tops and sides back every 4 to 6 weeks in order to keep the shape. You should do this each year.

Group 2 pruning

• When you plant, cut back the side shoots and leading should by a third.

• Repeat this again during the hedge’s second winter. This will prevent the growth from having a straggly appearance and will allow the hedge to grow thicker at its base.

• For maintenance trimming of an established hedge, you should trim it in June each year (or after it has flowered) and then trim it again in August. You should trim it so that the shape tapers towards the top.

Group 3 pruning

• When you plant these, you should leave the leading shoot of the hedge unpruned and should just cut side shoots that are straggly.

• During the summer, cut side shoots and tie the leader to a cane for support as it is growing.

• For evergreens with broad leaves like bay and laurel, you should use secateurs.

• For maintenance trimming, you should cut the hedge to your desired shape between one and three times during the summer until the end of August. If it is a yew hedge, you can continue clipping until September. You shouldn’t trim after this time because you will risk causing bare patches in your hedges. For evergreens with broad leaves like bay and laurel, use hand shears or secateurs. Make you cut the leading shoot at your desired height. Avoid the hard pruning of conifers as they will not re-grow from wood that is old.

Flowering and informal hedges

In order to encourage flowering the next year, you should prune informal hedges only once and at the right time. If you prune them at the wrong time, you will risk removing the growth that will grow flowers the following year.

For plants that flower on the growth of the current season (e.g. Fuchia), cut them once in the spring, allowing them to flower that year. In the summer, reduce the growth of the current season by half for plants that produce flowers on growth that is a year old (e.g. Pittosporum).

For berry-producing shrubs like Pyracantha and Cotoneaster, only trim when the berries have disappeared.