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Every gardener has stood in the garden at some point and thought, “That plant really needs cutting back.”
Pruning can help keep plants healthy, improve flowering and fruiting, control their size and encourage strong new growth. The difficult part is often knowing what to prune and when.
Different plants respond to pruning in different ways. A shrub that flowers in spring may need very different treatment from one that flowers in late summer, while some plants need little regular pruning at all.
You may also be dealing with a plant you did not choose yourself. Labels get lost, gardens are inherited and established shrubs can be difficult to identify, especially when they are not in flower.
This guide explains the basic principles of pruning, what to look for before making a cut and how flowering time and plant growth can help you decide when to prune.
Not every plant needs regular pruning, but there are several good reasons to reach for the secateurs.
Pruning can:
Before cutting anything back simply because it looks untidy, however, it is worth working out what the plant is doing and why you are pruning it.
If you know exactly what the plant is, check its individual pruning requirements before carrying out substantial pruning. The plant label is an excellent place to start, particularly if it gives the variety as well as the plant name.
Keep labels from new plants somewhere safe even if you remove them from the garden. Knowing exactly which rose, clematis, hydrangea or fruit variety you planted can make future care much easier.
If you have inherited a garden or the label has disappeared, you may not know what the plant is. In that case, don’t assume you need to prune it straight away.
Look for clues.
Flowering time can help you decide when a shrub is likely to need pruning.
Many shrubs that flower in spring and early summer produce their flower buds on stems that grew during the previous year. If you cut those stems back hard in autumn, winter or early spring, you may remove the following season’s flowers.
These shrubs are therefore commonly pruned after flowering. This gives them time to produce fresh growth that can mature and carry flowers the following year.
Forsythia, flowering currant and weigela are examples.
Many shrubs that flower later in summer produce their flowers on growth made during the current year. These can often be pruned in spring before that new flowering growth develops.
Buddleja is a familiar example.
These are useful general principles rather than rules for every flowering shrub. If you can identify the plant, always check its individual requirements.
The plant itself can give you useful information.
Before pruning, look for:
If you are unsure whether a stem is alive, gently scrape a very small area of the outer surface with a fingernail. Green tissue immediately underneath usually indicates living growth, while dry brown tissue may indicate that section has died.
Most importantly, if you cannot identify the plant and are unsure how it will respond, avoid drastic pruning until you know more.
Pruning instructions often tell gardeners that a plant flowers on either ‘old wood’ or ‘new wood’. Unfortunately, those terms can be confusing.
Old wood does not necessarily mean a thick, obviously ancient brown branch.
In pruning terms, old wood can simply mean growth made during a previous growing season. New wood usually refers to growth produced during the current growing season.
This matters because flower buds form differently on different plants.
A spring-flowering shrub may form its flower buds on stems it produced the previous summer. Those stems are now its ‘old wood’. Cut them away before spring and you may cut away the flowers too.
A later-flowering shrub may produce fresh stems in spring and then flower on those same stems during summer. That is flowering on ‘new wood’.
Rather than trying to judge the age of a branch purely by its colour, consider when the plant flowers and where you have previously seen flowers appearing.
As a general guide, many shrubs that flower in spring or early summer are pruned after flowering. This gives them time to make new growth that can carry flowers the following year.
Examples include forsythia, flowering currant, weigela and mock orange.
Many shrubs that flower later in summer are pruned in spring, as they flower on growth made during the current year. Buddleja and Caryopteris are familiar examples.
These are general guidelines rather than rules for every shrub. Hydrangeas, for example, vary in how and when they should be pruned, so see our Pruning Hydrangeas guide before cutting yours back.
Lavender also needs different treatment. Trim it after flowering to help maintain a compact shape, but avoid cutting hard into old bare stems.
Many established evergreen shrubs need relatively little routine pruning.
Dead, damaged or badly positioned growth can be removed when appropriate, while shrubs grown for a formal shape may need regular trimming.
Where pruning is required, many evergreen shrubs are pruned in spring, once the risk of severe frost has passed. Spring-flowering evergreens are generally left until after flowering.
Avoid assuming that an overgrown evergreen can simply be cut back hard. Some regenerate well from older wood, while others do not.
Pruning is not only about woody shrubs and trees. Herbaceous perennials also need occasional cutting back and tidying.
Whether to cut them back in autumn or leave them standing through winter partly depends on the plant and the conditions in your garden.
Seed heads and standing stems can provide winter interest, food for birds and shelter for insects. In wet conditions, however, some growth quickly collapses and becomes soggy.
These plants naturally die back over winter. Cut back dead or collapsed growth in autumn, or leave healthy stems and seed heads standing until spring for winter interest and wildlife.
Examples include:
• Delphiniums
• Hardy geraniums
• Phlox
• Peonies
Remove any remaining dead stems before new growth gets underway in spring.
Do not cut these plants back to ground level. Instead, remove dead, damaged or diseased foliage as needed.
Examples include:
• Hellebores
• Bergenias
• Some evergreen sedges
Some evergreen perennials have their own pruning requirements, so check individual plants before cutting back heavily.
Some less hardy perennials benefit from keeping much of their old growth over winter, as it can help protect the plant from cold weather.
Examples include:
• Penstemons
• Verbena bonariensis
• Some salvias
Pruning requirements vary, so check the individual plant. In many cases, the main cut back is best left until spring, when new growth makes it easier to see what has survived the winter.
Good pruning is not about removing as much growth as possible. Often, a few carefully chosen cuts are all that is needed.
Start by removing what gardeners sometimes call the three Ds:
You can then remove branches that cross or rub against each other and, where appropriate, thin congested growth.
When shortening a stem, make a clean cut just above a healthy bud or suitable side shoot. Where possible, choose a bud facing in the direction you want the new growth to develop.
Step back regularly while you work. It is much easier to remove another branch than to put one back.
For larger branches, use an appropriate pruning saw and remove the weight in stages to reduce the risk of the branch tearing and damaging the bark.
An established plant that has been neglected for several years can be tempting to cut right back in one go. Some plants respond well to hard pruning, but others may lose their flowers, produce masses of vigorous regrowth or recover poorly.
Many deciduous shrubs respond well to renovation pruning. Depending on the plant, this may mean hard pruning or gradually removing older stems over two or three years. Some evergreens and woody plants respond poorly to severe pruning.
If you don’t know what the plant is, identify it before attempting major renovation if you can. If you can’t, be cautious. Removing obviously dead or damaged material is very different from cutting an unidentified shrub almost to the ground.
If the plant is particularly old, unusual or important to you, consider taking cuttings before attempting major renovation.
Tree pruning needs a little more care because there is no single pruning season suitable for every tree.
Many deciduous trees can be pruned while dormant, when their branch structure is easy to see. However, there are important exceptions.
Cherries and plums are generally pruned during the growing season rather than winter because this reduces the risk of silver leaf disease. Magnolias and walnuts also have particular pruning requirements, while birches and acers can bleed sap heavily if pruned at the wrong time.
Before carrying out anything beyond the removal of small dead or damaged branches, identify the tree and check the recommended pruning period.
Large branches, mature trees and work that cannot be carried out safely from ground level are jobs for a suitably qualified tree professional.
For fruit trees, see our Guide to Pruning Fruit Trees.
There is no single month when everything in the garden should be pruned. These seasonal guidelines provide a useful starting point.
The timing and method of pruning roses depends on the type of rose you are growing. See our How to Prune Roses guide for more detailed advice.
For more detailed advice, see our Guide to Pruning Hedges and How to Grow and Prune Wisteria.
Avoid pruning during severe frost, and check the individual requirements of trees and shrubs before substantial pruning.
Before pruning shrubs, trees, climbers or hedges, always check carefully for nesting birds. Although the main nesting period is associated with spring and summer, birds do not work to a fixed gardening calendar. If you find or suspect an active nest, leave the pruning until the birds have finished nesting.
Pruning less aggressively can also benefit other garden wildlife.
Consider:
A garden does not have to be completely cut back and tidy to be healthy.
Using the right tool makes pruning easier and produces cleaner cuts.
Useful tools include:
Keep cutting tools sharp and clean. Dirty or blunt blades can damage stems and make pruning harder than it needs to be.
If you are unsure what a plant is or how it should be pruned, you do not have to cut it immediately.
Look at when it flowers. Watch where new shoots appear. Notice which stems carry flowers or fruit. Try to identify the plant and check its individual requirements before carrying out major pruning.
Pruning is much easier when you understand what the plant is doing, and sometimes the best pruning decision is simply to wait and watch.
Visit us in Kington for secateurs, pruning saws and other garden tools, seasonal plants and practical advice from our team.
