A formal hedge is one that is clipped regularly. Choose a dense, fine-leaved plant, such as privet or a conifer and make sure you trim it regularly to a squared or wedge shape with the base wider than the top. This allows maximum light to reach the base and makes it look more solid.
Try to keep the top no wider than about 60cm, so you can cut it easily from one side.
For longer hedges, erect a line using bamboo canes and string that doesn't stretch when pulled.
Push bamboo canes into the soil at either end of the hedge, and shorter canes at 45 degrees to these, pointing away from the hedge.
Tie a string line between the slanting and upright canes to stop the upright canes pulling inwards when you tighten the string along the hedge.
Tie the string above the hedge to get a straight side, and then about 1cm below the desired eventual height to cut the top.
Start trimming at the bottom of each side and work upwards in smooth, continuous swathes.
Cut the top of the hedge last.
Save time by spreading a plastic sheet beside the hedge to catch the clippings.
Brush or rake the clippings from the top of the hedge. If you leave them on the hedge, the damp, airless conditions they create could allow fungal diseases to get a hold.
Choose a large-leaved deciduous plant, such as forsythia, escallonia or berberis, which have bright flowers and berries, too. Native plants, such as hawthorn, blackthorn or field maple, are great for wildlife, while dog rose and sweet briar rose have attractive flowers and hips.
For a regular shape, cut back informal hedges after flowering.
If you prefer a more relaxed-looking hedge with berries and hips, cut back hard every few years.
You may prefer to cut these hedges with secateurs and loppers, selectively removing older branches for a more natural look.
If you have a lot of tall hedges to cut, invest in a special hedge-cutting platform with a wide base suitable for non-level ground. Ideally, it should be high enough that you can cut the top of the hedge at waist height. These are available from suppliers such as Henchman and Hedgemaster.
Alternatively, you could look for a long-reach hedge trimmer with telescopic handles that extend by an additional 20-30cm, or have a long fixed shaft. You can angle the blade at right angles to cut the top of a hedge (up to about 3 metres high).
Never lean a ladder against a hedge to cut the top. If you're using an ordinary step ladder, get someone to hold it steady for you.
How to renovate a hedge
Decide on the height or width you want, and use canes and string to mark this out before you start to cut.
You can cut back up to 30cm further than this, depending on the overall size of the hedge, to allow for new growth.
To retain a physical barrier, and to avoid shocking the plant, cut back one side of the hedge one year and the other side the next, especially on large hedges.
Use loppers or a pruning saw on older branches that are more than 1cm in diameter.
Once you've cut it back to the required size, trim regularly with a hedge trimmer.
All conifer hedges except yew should not be cut back beyond the green growth, as they won't regenerate. If your conifer hedge has grown too large, it may be time to replace it.
Can I use a hedge trimmer to cut branches?
You will often see claims that hedge trimmers can cut stems up to 33mm, but in practice we would not recommend using a hedge trimmer to cut such thick branches. If your hedge has branches larger than around 1cm, you will achieve a neater finish with loppers.
A hedge trimmer with a teeth width of around 20mm will be fine for twiggy hedges.
How to use a hedge trimmer safely
Always work from the ground where possible, on an even, dry surface.
If you need to cut a tall hedge, use a long-reach hedge trimmer or a platform.
Always use a residual current device (RCD) plug or adaptor to protect you from an electric shock if you do accidentally cut the cable, unless your whole house is protected by an RCD.
Keep the cable out the way by putting it over your shoulder so it hangs behind you, or attach it to your belt.
Make sure your extension cable is long enough to complete the job without stretching.
Wear safety goggles or a visor to protect your eyes from flying debris.
If you have young children, unplug a mains hedge trimmer at the mains, or remove the battery from a cordless trimmer, if you leave it unattended for any time.
Strong gloves and work boots with good grips are advisable.
If you have to trim hedges during the main nesting season – usually from March to the end of August – check for nesting birds first. Any nest site should be obvious from the frequent comings and goings, so keep an eye out for a few days before you plan to cut the hedge.
Delay trimming until you're sure the nestlings have flown. If in doubt, wait until the autumn.
Alternatives to using a hedge trimmer
For boundary hedges a powered hedge trimmer is the best choice.
For a smaller hedge, the environmentally friendly, low-tech option is a decent pair of hedging shears.
For a topiary, you can use ordinary garden shears, but topiary shears give a great finish. These can be used one-handed.
Large-leaved plants, such as laurels, can be difficult to trim cleanly with a hedge trimmer. Use a pair of shears to tidy up leaves left ragged by the trimmer.