Pruning is done for a variety of reasons – to promote bigger harvests, get newly-planted trees and shrubs off to a good start, thin crowded stems, train cordons, fans and espaliers, encourage flowering, shape plants, remove diseased wood and promote vigour.
With a few exceptions, all of these jobs can be done in winter, when bare stems make the job of shaping shrubs and spotting diseased growth much easier.
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We explain why you need to prune in winter and share tips on the best techniques, below.
Having established a framework, the object of pruning is to persuade the plants to maximise fruiting. This differs with various types of fruiting plant. With apples, you prune to promote fruiting spurs, with pears you open up the trees to ripen the wood.
Autumn-fruiting raspberries should have all stems cut back to the ground, then feed and mulch in spring. On summer-fruiting raspberries, cut out the canes that have already produced fruit, to leave the new canes that have been produced that year.
When shrubs or trees are newly planted it’s important to encourage formation of a good root system. New shrubs should be cut back to a few buds so that the plant can devote its energy to putting down roots in the first season. New fruit bushes should be thinned to just three branches. Newly planted trees should be pruned to reduce the ‘sail’ effect of top growth, preventing wind-rock.
On plants where growth is constantly renewed from ground level, the weak, spindly shoots should be removed, as well as some of the oldest stems. With plants such as hazel, the oldest shoots should be thinned out to prevent overcrowding. Simply remove large branches from older shrubs.
Training fruit trees
Having established the main framework by tying in major branches to the support, side shoots should be reduced to two or three buds to make short spurs. Much of the work should be done in August and September, but it can be continued into winter. Discover three ways to train a fruit tree.
Promoting summer blooms
Shrubs that flower after midsummer can produce flowers on new growth. They can be manipulated to ensure the flowers grow at the desired height. Branches can either be cut back hard or thinned into a nice shape. Large shrubs such as buddleia should be pruned hard to stop growth getting out of control, while smaller shrubs such as hardy fuchsias should be cut back to promote larger blooms.
Winter is the ideal time to assess and modify the shape and structure of almost any deciduous shrub whose canopy has become lopsided or whose branches are overcrowded in the centre.
Remove any stems that rub against each other, and aim to create an open-centred canopy that allows air to circulate freely. Use secateurs to cut stems that are up to 1cm in diameter, loppers on stems that are 1-2cm in diameter and a pruning saw on anything larger. Smaller stems can be cut flush with the branch from which they are being removed; those over 5cm in diameter should be left with a small knuckle – about 1cm of stem base – to aid wound healing.
Diseased branches should be pruned out to maintain the health of many trees and shrubs, removing any dead, dying or diseased branches. Apples and pears should be pruned to remove branches infected with canker, magnolias should have dead stems removed to control verticillium wilt. Don’t prune plums and related species during winter – it can lead to the spread of silver-leaf disease.
The stems of Japanese maples often turn pale grey and strawy-brown when wind damaged. Snip these out as soon as you see them, along with any stems that have been ‘ring-barked’ by disease lower down – you’ll see a pale grey patch of stem rather than a deep purple-brown bark on coloured-leaved types and the foliage above will lack vigour.
Pruning in this way removes weaker stems to promote stronger growth of existing stems, or removes existing stems altogether to encourage fresh, new growth.
Plants grown for their colourful winter stems, such as dogwood, Cornus alba, and white willow, Salix alba, should be cut back hard or ‘stooled’ in late winter or early spring, to around 15cm above ground level. Other shrubs should have the thinnest, spindly growth removed. Only start hard pruning these plants a year or so after planting, to allow their roots to get down into rich, moist soil.
Alternatively, just prune out half the stems, removing the oldest and leaving the youngest for the winter spectacle.
Rejuvenate a tired shrub
It’s a good idea to assess all your shrubs in winter, looking out for general tiredness and lack of vigour. This can often be attributed to hunger, in which case feeding and manuring in spring will help, but may also be down to the age of the stems.
Shrubs like weigela and philadelphus benefit from having some of the older stems removed each year to encourage new, more productive ones to grow up. You can also do this pruning in late spring and early summer, after flowering.
Use loppers to cut back these old stems either to ground level, or back to a point at which growth is emerging. Doing this annually will markedly improve the vigour of more mature shrubs.