Pruning your plants properly can provide you with the best show of leaves, flowers, fruits and form, so it’s useful to know which plants to cut back and when.
The basic rules of pruning rely on understanding your plants’ growth cycle. Herbaceous perennials and most summer-flowering shrubs have the ability to produce shoots that will be topped with flowers during the course of a single growing season. By contrast, shrubs, trees and fruit bushes that bloom in winter or spring carry their flowers on shoots produced from older stems and branches made in previous years.
It’s also worth remembering that cutting back woody plants when they’re dormant will tend to promote leafy growth, while shortening vigorous growth in midsummer will keep shrubs and trees more compact and encourage flowering.
Remember that such pruning is governed by what the plant is being grown for, or when it blooms. As for tools, a good quality pair of secateurs is well worth the investment, as well as loppers and a folding pruning saw for shoots with a larger diameter, plus shears to keep hedges and topiary trim.
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Follow the advice in this comprehensive guide for year-round pruning know-how.
Clematis texensis ‘Kaiu’
With cold temperatures and low light levels, the majority of plants that we grow in our gardens are in their dormant phase, although some have the ability to grow slowly and produce flowers in winter. Avoid pruning any plant when frost is forecast within three days, as the cut ends of the stems can be damaged before they have a chance to dry and seal off. Don’t cut into tender plants or evergreens in winter as their top growth provides insulation from penetrating cold.
What to prune in winter
Hard pruning a buddleia
- Hardy trees, shrubs and fruit bushes can be cut during frost-free weather
Group 3 clematis, such as viticellas, Clematis orientalis and some of the late-summer flowering hybrids need reducing
- Thin out branches and fruit spurs of top fruit, such as apples and pears
- Carry out formative pruning of young hardy shrubs and trees – remove thin, twiggy growth and reduce the remaining growth by half its length to encourage a strong framework of new shoots
- Summer-flowering shrubs, such as buddleia, Hydrangea paniculata and lavatera can be cut back hard in late winter, just before they start into growth in the spring
- Early to midwinter is your last chance to cut back woody plants prone to ‘bleeding’ sap – such as birches, walnuts and grapevines – as they bleed if pruned late
- Prune the dead stems of herbaceous perennials at the end of winter to tidy beds and make way for new spring shoots
Cutting back rose bushes – large-flowered (hybrid tea) and cluster-flowered (floribunda) roses – in late winter is crucial for the promotion of strong shoots low down on the plants with a wealth of blooms in summer
Pruning a grapevine in a winter
Grapevine sap starts to flow in late winter/early spring. If cut then, sap will bleed from the plant, causing a serious loss in vigour. Test before pruning by making a small cut to see if bleeding will happen. If not, you’re safe. For winter pruning, trim back side branches back to two buds to encourage the production of fruiting spurs.
- Tender shrubs including abutilon, bottlebrush, cistus, Convolvulus cneorum, lavender, leptospermum, phlomis and teucrium
- Evergreens such as hebe, escallonia, pieris, pittosporum and rhododendron
Cherries, plums and greengages as, at this time of year, cuts can be more susceptible to infection with silver leaf disease
Purple moor grass (Molinia caerulea)
Warmer days and increasing day length encourage plants into active growth during spring. Stored starch turns into sugars that promote the flow of water (sap) up through the stems, causing buds to open into leaves and, in some cases, flowers. Foliage can capture energy from the sun, making more sugars that fuel growth. Spring arrives early in the south and west, and later in the north, east and at higher altitudes, so pruning should be timed according to local conditions when risk of severe frost has passed.
What to prune in spring
- Cut back or coppice shrubs grown for large decorative leaves (catalpa, cotinus, paulownia and sambucus) or their coloured winter stems (cornus, white-stemmed bramble and willow)
- Prune off the old, dead stems of ornamental grasses before new growth starts vigorously from the base
- Take out some of the oldest stems and branches from evergreen shrubs such as winter-flowering camellias, hollies, photinia, mahonia and pittosporum as soon as the risk of heavy frost has receded
- Deciduous shrubs that bloom after autumn leaf fall through until late May can be pruned in spring, after flowering. Cut out the oldest, flowered wood and any weak, spindly growth, to leave a proportion of vigorous, younger stems and to make way for new growth, which will go onto bloom in the following season
Chelsea chopping an aster
Cut back the new stems of late-summer flowering perennials by between a third and half their height in late spring. This will promote sideshoots that’ll carry more flowers and reduce the need for staking plants. This treatment is called the Chelsea chop, as it’s done around the time of the flower show. Helenium, phlox and sedum will respond well.
- Spring/early summer-flowering plants that have yet to flower, such as deutzia and philadelphus, both of which bloom at the end of this season and which can be cut back after flowering in late May or even in June. If you’re not sure, watch how your shrub grows this year
- Fruit trees and bushes as you may well be cutting off flower buds and/or developing fruit
Trimming a pittosporum hedge
Hot days and warm nights encourage strong growth as long as there’s sufficient moisture available in the soil. High light levels and long days allow lots of sugars to be made in the foliage through the process of photosynthesis. Growth slows in midsummer and the soft, green shoots of trees, shrubs and fruit bushes start to ‘ripen’ (or stiffen) in the heat of the sun, gradually becoming woody by the end of summer.
What to prune in summer
Summer pruning wisteria
- Cut back the flowered stems of spring-flowering perennials, such as bergenia, brunnera, lamprocapnos, hellebores, peonies and pulmonaria to channel energy into the plant rather than seed production. You can also cut back early-summer perennials such as alchemilla, astrantia, delphiniums, geraniums and lupins after flowering, which should go on to produce a second flush of flowers
Trim hedges as soon as the flush of new growth has started to stiffen at the base and after any young birds have fledged from their nests
Bush fruit can be pruned immediately after cropping, removing the old, fruited stems and leaving the strongest current season’s new growth that will overwinter to crop in the following year
Pruning fruit in summer
Summer pruning an apple tree
Pruning back the current season’s growth of apples, cherries, pears and plums will keep the trees compact, and promote the production of more flowers and fruit in subsequent years. Cut all the soft, green shoots back to two or three leaves from their base in July. This will also let sunlight through and channel available moisture to the developing fruit.
Hydrangea aspera subsp. sargentiana
- Late-summer-flowering shrubs, such as hydrangeas, unless it’s just to deadhead old flowers to encourage more to come
- Plants that bleed sap in summer, such as acers (cut back between leaf fall and late January) but snakebark maples like Acer davidii can be pruned in late summer, and mulberries – prune any time from autumn to early winter
Cool nights and shortening days drastically reduce the growth of plants and, in the case of deciduous plants, cause leaves to fall from the stems. The current season’s stems of woody plants continue to ripen during autumn in moderate daytime temperatures, toughening up to survive the onslaught of winter, with buds forming a resilient outer coating to protect their contents.
What to prune in autumn
Pruning a blackcurrant bush
- In windy areas, cut back flowering shrubs and fruit bushes to prevent wind-rock of the plant during the ensuing winter, and to encourage growth from low down on the plant in the following spring. Reduce the size of rose bushes by around half their height to prevent them rocking about in strong winter winds. The stems can then be cut back harder in late winter, when they have done their job of protecting the lower buds from heavy frost
- Hardy climbers such as honeysuckle, Virginia creeper and wisteria, having performed in summer, can be reduced in size by cutting back the vigorous sideshoots to around three buds above the base. This will also reduce the weight of the plant on its supports to prevent damage in autumn and winter gales
- Prune autumn-fruiting raspberries, blackberries and hybrid berries as soon as the last fruits have been picked. This will allow the old, fruited canes to be removed and the new stems trained into their supports
- Once the leaves have fallen from deciduous trees and shrubs, you’ll be able to see the structure of branches and stems. Check for any crowded stems or crossing branches, thinning out the centre of the plants. Take time to prune back any dead, damaged or weak branches, too
Pruning summer raspberries
Pruning summer-fruiting raspberry ‘Glen Rosa’
Summer-fruiting raspberries produce fruit on one-year-old canes. Cut down all the canes that produced fruit this year. Retain six to eight of the strongest new canes per plant. These will look lush and green (see above). These remaining canes should be tied with soft string into their wire supports. Ideally, they will each be spaced about 10cm apart along a horizontal wire support.
- Tender border and wall shrubs such as oleander as this will promote late regrowth that is soft and vulnerable to frost and wind damage in the coming winter
- The majority of border perennials and ornamental grasses can be left uncut, their top growth protecting the crown of the plants in winter and providing shelter for garden wildlife