Hedging plants are often described as ‘the architecture of the garden’. But how to keep them healthy and looking good?
Houzz UK contributor and award-winning landscape and garden designer. Claudia de… More
Pruning is a huge subject and it can be confusing to know when and how to do it. Here are a few tips for helping you get the best from some of the most popular varieties of hedging plants.
Many hedging plants are cheap to buy in the late autumn as young plants or ‘whips’, and they not only provide an attractive green boundary and give the garden good structure, they’re also wonderful for wildlife. The RHS has divided woody shrub pruning into 13 groups, and hedging falls into several of these, depending on whether the plant is evergreen or deciduous and which variety you’ve selected from the many shrubs available.
Always check for nesting birds before you do any pruning.
Deciduous hedging is pruned in summer to stop plants becoming unruly – this is considered maintenance pruning. In winter, deciduous shrubs, which shed their leaves, can be reshaped by cutting back hard.
When you start pruning a large hedge, trim from the bottom to the top. This is very important, as it allows more sunlight to reach the bottom of the plants.
You’re aiming eventually to have cut the hedge into an A shape; the slope you create is known as a ‘batter’. If you just cut upwards in a straight line, the top of the hedge, which always gets more sunlight anyway, will shade the base and you’ll have a plant that’s weaker at the bottom.
Beech and hornbeam (carpinus betulus) hedging is best trimmed in August or September, as this will enhance the winter appearance and help to keep leaves on the branches for longer. Cut both hedges again in February if you want to keep them crisp.
Most people say it’s best to use secateurs or hand shears for this type of hedge, so you don’t tear into the leaf, making it turn brown. Whichever tool you choose, prune back the new long shoots at an angle to two or three leaves from its base.
Read a beginner’s guide to pruning
Box (Buxus) falls into RHS pruning group 8, the early flowering evergreens that also include plants such as camellia and Viburnum tinus.
There’s a great deal of debate about when to prune box, not least because of all the problems now associated with it in terms of disease. Some say cutting the tops to a 45-degree angle avoids blight settling on a flat-topped hedge. And the good news is that box, like holly and yew, will regrow from bare wood; it’ll look unsightly until the following spring, but will then resprout with fresh new shoots.
Dipping your shears’ blades into diluted bleach will also help to prevent any disease spreading.
For young, newly planted hedges, cut back in May to encourage new bushy growth. Prune back the new season’s growth when it’s around 10cm long.
For older, established hedges, you can cut in May or June, but any adverse weather conditions, such as scorch or late frosts, may affect young growth, allowing disease to enter. As such, you may prefer to prune them in August/September, when any new growth has hardened off.
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Young, bare-root hedging plants
These are called ‘whips’. For a good, informal-looking and wildlife-friendly hedge, consider planting hawthorn (Crataegus monogyna). Once established, it produces lovely white, scented blossom in May, followed by red berries in the autumn, ideal for birds.
You can buy whips from October to March and smaller plants often knit together better, forming a thicker hedge than larger individual shrubs.
Young, bare-rooted plants are called whips due to their long, slim appearance. They tend not to have side branches, and this makes it easier to attach a spiral guard against nibbling rabbits to the upright stem; you may need to do this until the plants are well established.
When planting young hedging plants, you need to be brutal and cut them back by half to encourage vigorous regrowth and low branching. By spring, the dormant buds below the cuts you made will start to pop out. The following winter, do the same and cut it back by half.
As with other pruning advice for hedging, make sure the bottom is always wider than the top to allow light into the lower branches to keep them leafy.
Yew (Taxus baccata) is a forgiving hedge when it comes to pruning. These are slow-growing plants, but they make wonderful thick hedges, which also lend themselves to topiary.
If you’re planting young hedging plants from October to March, trim back any straggly side growth, but don’t cut the top growing point or your plant will never recover the same vigour or grow properly in height.
For the first few years, trim your hedge in April, July and October in a tapered shape, allowing light to get to the base. When you have the desired height, let it grow to around 10cm higher than you want and then you can start to reduce the top slowly, little by little.
Make sure when you plant your yew, the soil is well-drained, as it will not tolerate water- logging and could be susceptible to Phytophthora root rot.
To renew an old yew hedge, you can coppice it, which means being brutal and cutting it down almost to ground level – 15-25cm – in early spring. New growth will be produced, but it could take a few years to recover properly.
Check out 10 ways to keep your home ticking over throughout winter
Tools and tips for the job
Spending a bit more on the correct tools for the job is a worthwhile investment. There’s an abundance of quality, hand-held shears and loppers on the market, as well as various battery- or petrol-powered units.
Take time to select the right option for you; depending on the application required, this should also take into account weight and comfort.
Do wear ear protection when cutting hedges, as well as eye protection, as small pieces of the cut branch can often fly out of machinery.
If you’re using an electrical hedge trimmer, make sure you have an RCD safety adaptor (circuit breaker) attached to protect you in case you cut through the wire. Don’t work for longer than an hour at a time, as you may feel a bit breathless and dizzy, especially if working at height. Also, it sounds obvious, but do make sure your stepladder is up to the job and not wonky – and never lean into a hedge.
To help protect your hedge, make sure you have clean, sharp blades to prevent it becoming bruised or stringy as you prune.
When you feel you’ve cut your hedge sufficiently on one side, use a spring rake to tap against it. This will make any folded long ends spring out so you can catch them in a final tidy.
Informal flowering hedges
There are some lovely plants that can be used as hedging. Evergreen examples include shrubs such as Pyracantha, cotoneaster, escallonia and lavender. Most of these plants are best pruned after flowering or fruiting.
- Pyracantha flowers on the previous year’s growth, so when you prune in the spring after flowering, try not to remove too much of the past two years’ growth. Make sure you have thick gloves on when pruning Pyracantha as it has sharp thorns.
- Cotoneaster is a great wildlife hedge, but the variety will dictate when it needs trimming. Cotoneaster franchetii, for example, only requires light pruning after the berries have fallen.
- Escallonia is best pruned after flowering, but you can keep it trim throughout the year with regular cuts, as some varieties grow quite quickly and need to be kept in check.
- Lavender doesn’t break well from old wood and you may find that after a few years, some plants become so leggy and woody they need replacing. The main pruning is done after flowering in late summer. Cut off the old flower stalks with secateurs or hand shears, then go back over the plants, trimming back to about 3cm, leaving some fresh new growth; avoid going into old wood.
- Deciduous flowering hedging plants such as Rosa rugosa are pruned in spring, when you simply thin out any leggy growth.
- Forsythia is a plant that heralds spring and should be pruned by removing stems that have flowered right back to a healthy pair of buds. You can also cut out one in every three stems right back to the ground to encourage basal shoots to grow.
Conifers and Leylandii do not like being pruned hard. A hard prune will lead to bare brown stems in the middle of the plant and unsightly patches in places that will inevitably fail to green up.
- As a plant for a dense hedge, Thuja, also part of the cypress family, is better at being pruned, but, as with the other evergreens, the time to do any cutting is in the spring (March/April) before the first flush of new growth. Some conifers can irritate the skin, so wear long sleeves and gloves when cutting.
- Privet (Ligustrum ovalifolium) can cope with hard pruning. For a new hedge, it’s best to buy bare-rooted plants, as they establish very fast. Prune young plants by a third once they’ve settled a bit and have rooted in, as this will make them bushier at the base.
- Laurel (Prunus laurocerasus) is so tough, it can be cut back as hard as you like. If you want your laurel to flower annually, prune straight after flowering for buds the following year. Portugal laurel (Prunus lusitanica) is also very forgiving when it comes to being pruned, and it will flower if you leave your trimming until late June.
- In order to stop a newly planted Leyland cypress (Leylandii) hedge from getting out of hand early on, in the first and second year, trim back long side shoots in April and July. Make sure you’ve tied in the leader (the main dominant stem of the plant) to a cane to encourage the plant to grow up straight. Keep trimming the side shoots until the plant has reached the desired height.
In the spring, once the hedge is the correct height, cut back the leading shoots to around 15cm below the height you want to achieve, as the new growth will promote a fuller top.
- If you want to reduce an established hedge, the best time to prune is early April, before any new growth. And don’t cut any more than one third of the height to avoid a bare flat top.
As evergreen hedging plants are, by nature, never really properly dormant, do not prune any of them straight after planting, as you’ll only invite infection into the wounds before the plant has had time to root properly.
There are many varieties of variegated foliage shrubs that can be used for hedging, such as Ilex ‘Argentea marginata’, Euonymus fortunei ‘Emerald’,
Pittosporum tenuifolium ‘Variegatum’, and Cornus alba ‘Elegantissima’ to name a few. When to prune will depend on the variety of variegated shrub you have.
Photinia fraseri ‘Red Robin’ falls under the evergreen group of hedging plants, which means it should not be pruned when it’s dormant but in the growing season. Photinia is widely used for its vibrant red foliage, and regular trimming in spring and summer will help to keep a neat hedge shape. Don’t cut later than August, however, as any new foliage will be susceptible to frosts.
You can hard prune a very old Photinia hedge to around 60cm above the ground around May and it should soon recover and produce new foliage.
Have you picked up any pruning tips to share with other Houzzers? Let us know in the Comments section.