Pruning Soft Fruit and Fruit Trees
Cut Back with Confidence
Pruning is one of the most important jobs for the fruit gardener, yet unless it is done correctly it can lead to all sorts of problems. I am often told that it seems quite straightforward when reading about it, but as soon as you are standing in front of a tree or bush, secateurs in hand, your confidence vanishes. As valuable as books are, with their rule of thumb guides to pruning, I am convinced that the subject becomes much more straightforward if you appreciate the principles first and understand how different plants respond, and only then put theory into practice.
So why prune fruit trees? Consider what happens if we don’t. The tree will initially continue to grow happily, but as time goes on, it will set more and more fruit — very small and of poor quality — and produce less and less growth. In fact, it will lose the balance that must be maintained to produce quality fruit and healthy plants. On the other hand, if you overprune — easily done once you have started and got up steam — the balance swings the other way, and the tree produces too much vegetative growth and too little fruit. In practice it pays to prune lightly in the early years to encourage the plant to set fruit, pruning more heavily after it has carried several good crops.
Maintaining the balance is the main reason for pruning, but there are also other reasons: to allow light to get into the plant because shade results in poorer fruit the following year, and to provide good air circulation within the plant which helps prevent diseases. You will, even so, get some pest and disease problems so the more ‘open’ the plant, the easier the penetration of pesticide and fungicide sprays. As the plant develops, some branches may nevertheless become severely diseased; these should be removed along with those growing awkwardly in the wrong place.
But what actually happens when a branch is pruned? Obviously its length is reduced, but the harder it is pruned, that is, the further it is cut back, the more you will increase vegetative growth and the stiffness of the remaining branch. This applies particularly to winter pruning (when the buds are dormant). On the other hand, summer pruning, usually carried out when growth has almost stopped, does not encourage growth and is therefore used on intensive training systems such as espaliers and cordons.
These systems are very popular with gardeners, although they need attention, especially initially, and they can also be a little slow coming into cropping. Most trees are easier to manage if you encourage their natural growth habit, and for tree fruits this means a tree with a central stem rather like a Christmas tree. With most varieties of fruit, this tree habit is easy to maintain, especially if you bear in mind the fact that the more vertically a branch grows the more vigorously its grows, whereas a branch growing more or less horizontally will not be vigorous and will readily produce fruit buds.
As this sort of tree grows, fruit will be borne on the lower branches where it is easily reached while much of the shoot growth will be nearer the top of the tree. To maintain a balance of fruiting and shoot growth at the lower branches, the top of the tree should be used as the controlling mechanism, allowing it to grow away. This then reduces the vigour of the tree lower down. Alternatively, you can prune the central leader to a fruiting branch to induce vigour and maintain fruit size lower down.
If you find that you are short of space or prefer decorative shapes, apples and pears in particular can be grown as cordons or espaliers. Cordons can be grown against fences or walls, as well as in the open along wires, whereas espaliers are particularly effective against walls or along wires.
Plums and cherries can be grown as centre leader trees, as described for apples and pears, but with these and other stone fruits, such as peaches and nectarines, the most important point to remember is never to prune during winter as this will increase the risk of infection from bacterial canker and silver leaf diseases. Similarly, it is important that whatever training system is adopted, ties and so on must not damage the shoots leaving wounds through which disease can enter.
Plums and cherries respond well to fan training, a system that is especially suitable for peaches and nectarines grown against the south face of a wall. You may prefer to buy trees trained as fans by the nurseryman or start from scratch yourself.
If you move house and find yourself saddled with sadly neglected trees, there are remedies. If the tree is producing lots of fruit bud and little shoot growth, the fruiting spurs should be thinned by pruning each to a few buds only and spacing the retained spurs 10cm (4in) or so apart. This, coupled with the removal of branches, should stimulate shoot growth and regain the balance between fruiting and growth.
On the other hand, you may have trees that are growing very vigorously and producing no fruit. This may be due to over-enthusiastic pruning, too vigorous a root stock, a tree planted too deep so that the variety has rooted, or, as so often happens, insufficient pollination is provided to set fruit. To redress the balance, cut out overcrowded shoots and branches, in late summer; do not feed the tree; allow grass to grow around it; and make sure that adequate pollination is provided.
Pruning soft fruit is much more straightforward. With summer-fruiting raspberries, for instance, all that is required is to cut to ground level cane that has carried a crop. The remaining cane, which will fruit the following year, should be thinned leaving eight to ten of the strongest and healthiest canes per plant. These canes should then be tied to the wirework, preferably before winter is too advanced. Autumn-fruiting varieties of raspberry produce fruit on the current season’s growth and are therefore pruned differently. When fruiting has ceased they should be cut down to ground level and new cane will shoot up in spring.
Blackberries and loganberries crop on the previous year’s growth and so are pruned in the same way as summer-fruiting raspberries. Although blackcurrants produce fruit on all wood except the current year’s growth, the best quality fruit is borne on the previous year’s growth. It is important therefore to cut out shoots comprising mainly older wood and stimulate a cycle of new growth.
Redcurrents and gooseberries fruit on older wood at the bases of the previous season’s growth.
If grown as bushes, a permanent framework of branches is required, but once established, all new growth should be pruned back to a couple of buds. As these two fruits respond so well to this method, known as ‘spur pruning’, they also do well when grown as cordons.
There is no mystique in pruning. Study the fruiting habit of each type of fruit and adjust your pruning to produce the balanced growth so necessary for top-quality fruit.