How to prune garden shrubs

Most shrubs benefit from regular pruning to remove old wood, improve shape and encourage flower.

For many people, pruning is a mysterious art and plants are allowed to grow rampantly rather than given an annual trim. But there is no need for pruning to be a tricky task - with a little bit of knowledge, and a pair of secateurs, it's easy to tackle most garden shrubs.

Why prune shrubs?

There are several reasons why it is important to prune evergreen and deciduous shrubs. If a plant becomes a tangle of overgrown branches it is more likely to succumb to pests and diseases, and will become less vigorous, resulting in a poor display of flowers.

Cutting back shrubs regularly also helps to maintain an attractive shape and prevents plants from suffocating more compact neighbours, such as flowering perennials.

In small gardens, where space is at a premium, pruning is also necessarily to keep the plant within bounds.

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When is the best time to prune shrubs?

When best to prune will depend on when the shrub flowers. Generally if it flowers before mid-June it should be pruned straight after flowering. However, if it blooms later in the year wait until late winter or early spring.

Lavender, roses, fuchsias, caryopteris, buddleja and other shrubs that flower on the current season's wood should be pruned in early spring - this will give them plenty of time to form new branches that carry summer blooms.

Shrubs that flower in early summer on wood formed the year before, such as philadelphus, weigela and deutzia should be trimmed when blooms fade.

Evergreen shrubs are best pruned between late spring and autumn.

How to prune a shrub

Although some shrubs need specialist treatment, all of them can have the three D's removed first - dead, damaged or diseased wood.

Next snip out thin, whippy growth and if the plant is heavily congested, remove one or two of the older, thicker branches as well - this will allow air to flow freely through the plant.

Shrubs that flower on new growth can be pruned quite hard and many, such as buddleia and fuchsias, respond well to being cut back to a low framework, leaving one or two buds per stem - cut cleanly just above the bud.

Patio, cluster and large flowered roses can be reduced by two thirds – prune just above an outward facing bud, making a sloping cut away from the bud. This will prevent water from running into the bud and causing it to rot.

Other plants to prune in spring include dogwood or cornus, which are grown for their colourful winter stems. These can be cut back hard, to leave about two sets of bud per stem.

Overgrown mophead and lacecap hydrangeas can be tamed as the buds begin to swell - remove all of the old flower heads by cutting to the nearest pair of healthy buds.

Evergreen and deciduous shrubs that flower in early summer can be treated less harshly. Prune to keep within bounds and to maintain an attractive shape.

Rejuvenating an overgrown shrub

Sometimes when you take over a garden the shrubs have been allowed to become old and leggy. Stand back and watch for a year to see what you have in your garden. Then you can make a decision about whether you want to keep it or not.

If you decide to scrap it, autumn is generally the easiest time to get something out. It also allows you a couple months to decide what to replace it with in the following spring.

If you decide to keep it, you will need to do some radical pruning (probably in early spring) and this may result in the shrub dying. You could take some insurance cuttings in late-summer and autumn. Look for new growth that doesn't have any flower. If the wood is hard and brown, sink the foot-long cuttings into a trench in the garden. Just get a spade when the soil is damp and make a narrow gap by 'waggling' the spade. Leave the cuttings for a year. If you are on heavy soil dig a narrow trench and put sand into the bottom of the trench to aid rooting. semi-ripe cuttings that are still pliable can be trimmed under the node and plunged in a 50% mix of grit and compost. Leave them to root in the greenhouse away from overhead sun.

The rejuvenation involves two or three stages and will take at least two years. In the first year, prune deciduous shrubs by taking a third of the wood back to the base and leaving two-thirds intact. Take another third in the following year and then the remaining third in the next. This is an excellent technique and you will end up with a vigorous plant if the shrub responds. You will know after the a year whether it is working.

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Pruning evergreens

A few evergreens (like yew) respond to the three-year regime, as conifers will not regenerate from old wood.

If you are dealing with an overgrown holly it is not fast growing enough to spring up from the base and grow away quickly. Hollies are slow-growing and they need to be hat-racked. This preserves the height and ‘hat-racking’ can also be used with yew trees.

This is done in two stages. Begin by reducing the width of the yew or holly by cutting back most of the branches to eighteen inches or two feet in length. The bare stems radiate from the trunk and resemble a hat rack, or mug tree. The dormant buds respond and soon grow away and bush out. Leave the tree to recover and fill out for two years before reducing the height. At this stage you can cut the top off and you will end up with a rejuvenated holly or yew.

How (and why) to lift a shrub's skirt

The skirts are the lower branches of shrubs and trees and the idea of 'lifting skirts' is that by removing some of these lower branches you allow more sunlight through to the ground below where little woodlanders or other low growing plants might be struggling to get light. All kinds of ground cover and woodland plants will thrive in the dappled shade, so it's a great option for gardens where space is at a premium.

The other benefit of lifting the skirt is that you reveal more of the trunk or stem, which can look more elegant in a minimal way, reminiscent of a Japanese-style garden.

To start, consider how you want the shrub to look when you’re finished and keep stopping and standing back as you prune. Take your time.

Using a sharp clean pruning saw, loppers or secateurs remove some of the lowest branches thus raising the canopy. Only you can judge how much to take. If you're nervous about taking off too much at once you can always stop and leave the job for a couple of days to see how it looks with fresh eyes. If you need to take out more you can - but you can’t glue branches back on.

Tidy up the main stem by removing unwanted wispy side shoots.

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