Chapter 8

Pruning fruit trees

The art of pruning holds an air of mystique for many people; indeed, it can even put people off growing fruit trees, because they imagine that they will have to learn complicated techniques and spend hours putting them into practice. These techniques certainly exist, but it is more important to understand why fruit trees are pruned and what happens when you make a pruning cut.

This chapter examines the reasons for pruning fruit trees and looks at the principles behind pruning. Formative pruning and the various forms of fruit trees are also discussed. Specific information on pruning individual fruits is contained in the chapters in Part 3.

Why prune fruit trees?

One way to find out why fruit trees are pruned is to look at what happens when a tree is not pruned. The photograph on the right shows a plum tree that is only five years old; it has never been pruned and, despite its tender years, it already has a number of branches growing in an unruly fashion that will hit each other as soon as a strong wind blows. As the tree grows, it is likely to become a mass of tangled branches; it will still fruit, but little sunlight will find its way to much of the tree where it is needed to ripen the fruit. Long, unpruned branches will break in the wind or through the weight of a heavy crop, and disease is likely to enter when broken branches are not pruned back to leave a clean cut. Over time, fruit on an unpruned tree tends to become smaller and suffer from fungal diseases, which thrive in the moist environment that arises when there is little airflow through the tree.

A five-year-old plum tree that has never been pruned.

There are many reasons for pruning:

The principles of pruning

Pruning fruit trees is a subject that seems to be shrouded in mystery. Many people, not really knowing where to start, are afraid of damaging their trees; others complain that their trees don’t look like ‘the trees in the book’. There is some truth behind these remarks: it is possible to harm fruit trees, either by pruning too hard, or pruning at the wrong time of year, but clear instructions and an understanding of the principles of pruning will allow you to make judicious cuts that will help your trees to prosper.

It is very likely that your trees will not look like those ‘in the book’ – the directions given for pruning aim to give clear instructions for all situations, but each tree is an individual; rather than following detailed advice slavishly, it is much better to gain an understanding of the principles involved, so that you can work with your own unique tree rather than trying to impose a system on it. To some knowledgeable people, the advice on pruning in this book will seem oversimplified. This is deliberate, because it is better to understand the basic principles than to become confused by dogmatic and complicated instructions.

The photo below shows fruit and leaf buds on a branch of a plum tree. The fruit buds are swollen, slightly pointed, and protrude from the branch (most of those in the photo are fruit buds), whereas the leaf buds are more rounded and tight into the wood that they spring from. They emerge as leaves when growth commences, whereas fruit buds turn into flowers, and will eventually fruit if they are pollinated. It can be important to differentiate between the two when pruning.

A plum tree branch, showing the fruit and leaf buds.

GLOSSARY OF THE DIFFERENT PARTS OF A FRUIT TREE

Diagram 15 shows the constituent parts of an apple tree, but most fruit trees are similar, except that the fruiting spurs are particularly pronounced on apples and pears.

The trunk is the main woody stem that emerges from the ground. The union is a swelling, usually low down on the trunk, where the scion was grafted on to the rootstock when the tree was formed.

A framework branch is a large branch growing from the trunk. This is one of the branches that are selected during formative pruning.

A lateral is a branch growing from a framework (or main) branch, or from the trunk.

A sublateral is a side shoot growing from a lateral.

A fruiting spur is a shoot on which fruit buds form.

The central leader is the upright growth at the top of the trunk.

A branch leader is the new (or extension) growth at the end of the branch.

Diagram 15 The different parts of a grafted fruit tree.

It is also important to be able to identify the current year’s growth (or extension growth) when pruning. Often you will be asked to remove a proportion of the current year’s growth. You can identify this by finding the rings that form between each year’s growth (see Diagram 17, page 102) and by looking for subtle changes in the colour of the bark.

Diagram 16 The effect of pruning on apical dominance.

Apical dominance

Apical dominance is the tendency of a shoot to continue strong upright growth. Diagram 16 shows how the apical dominance present in (a) is broken when a pruning cut is made: the growth that was strongly upwards through the terminal bud is now changed, so that the side shoots (or lateral buds) now grow more strongly. When you make a pruning cut, you are not only removing unwanted growth but also causing a change in the growth pattern of the branch that remains.

This principle can be used when forming a young tree into a goblet shape. The cut made in (b) will encourage the laterals to grow strongly, helping to produce a more spreading tree.

Pruning lightly or hard

Every time we make a cut, the tree will try to respond by sending out more growth – either from close to the cut, or further down the remaining branch. You can use this principle to help create more growth or fruiting shoots in a place where you would like them. Successful fruit tree pruning involves creating the right balance between fruiting and vegetative growth. Vigorous growth is usually vegetative (although it can become fruitful later on). The balance is achieved by pruning vigorous growth lightly and weaker growth harder. This is something that can be difficult for the beginner to grasp, as it can be tempting to cut the strongest growth the hardest. In the same fashion, a vigorous tree needs only light pruning, whereas pruning a weak tree a little harder will encourage stronger growth.

To gain an understanding of the vigour of the tree, look at the new growth at the top of it. Look to see how much the tree has grown in the last year. Is this new growth strong and vigorous, or weak and spindly? Diagram 17 overleaf shows how to spot the growth rings that enable you to see the last year’s growth.

Diagram 17 The features of a young apple or pear branch.

However, if you prune a tree too hard it will try to send out more growth to compensate. The harder you prune, the more vigorous the regrowth will be. If you continue this process over a few years, you will end up with a tree like the one in the photo below. Unfortunately, the upright shoots produced are vegetative rather than fruiting growth, so the end result is a congested tree without much fruit. Overpruning is the most common cause of fruit trees bearing small crops. It is difficult to limit a tree’s size through pruning; instead, the size of the tree should be determined by the rootstock on which it is grown. Pruning lightly is much less likely to harm a tree, so it is always a good maxim to be sure that you know why you are making any particular cut – that way you are less likely to damage the tree by heavy pruning. It is much better to prune a tree lightly every year than to prune it more heavily every few years. A maximum of 15 per cent of the growth should be pruned off in any one year. This can be extended to 20 per cent when renovating a crowded tree. These figures do not apply to formative pruning (see page 108) or pruning restricted tree forms.

This apple tree has been pruned too hard, resulting in vigorous upright regrowth that bears little fruit.

Diagram 18 The growth resulting from pruning cuts made in the previous winter.

Achieving the correct balance between fruiting and vegetative growth is something that comes with experience. You might not get it right first time, but watching how the tree responds to your pruning will enable you to refine your techniques over time (see Diagram 18). In order to learn, you can take a photo of a particular branch before and after pruning and then return a year later to see how the tree has responded. (Tying a ribbon on the branch will enable you to find it again in a year’s time.)

Pruning at the correct time of year

It is vital to prune fruit trees at the right time of year, both to have the desired effect on growth and to prevent diseases that can become established if pruning is done at the wrong time.

The pome fruits (apple, pear, quince and medlar) are normally pruned in the winter, which encourages more growth, but there are exceptions to this rule, as follows.

Stone fruits (plums, peaches, nectarines, cherries and apricots) are pruned during the spring and summer, when they are actively growing, in order to prevent disease problems that could arise from winter pruning. Formative pruning of stone fruits can be carried out in the spring, just after bud burst, whereas mature trees are normally pruned during the summer.

Some trees, such as mulberries, will weep sap if pruned at the wrong time of year. The correct time of year for pruning all fruit trees can be found in the chapters on individual fruits in Part 3.

It is always best to prune on a dry day. Some fruit tree diseases are spread by wind and rain. Pruning wounds are the ideal surface for these diseases to establish and find their way into the tree. It is also worth avoiding days when the temperature is below freezing.

Pruning techniques

Learning how to make pruning cuts in the correct fashion will ensure that your pruning has the desired effect, rather than opening the tree up to disease and potential structural weakness.

Using secateurs to prune to an outward-facing bud.

Small pruning cuts

Small cuts are those made with secateurs, usually to a particular bud whose growth you want to encourage.

When cutting to a bud, the cut should be gently sloping, slightly above the bud. Cutting to a bud will encourage that bud to grow on, so the direction that the bud is facing will determine the future direction that the branch takes. For this reason, pruning is usually to an outward-facing bud, encouraging growth towards the outside of the tree (see Diagram 19). However, it is not only the topmost bud that will shoot after pruning; the first two or three buds are likely to form strong shoots. A bud that is likely to form a shoot heading in the ‘wrong’ direction, usually inwards, towards the middle of the tree, can be rubbed out with your finger at the time of pruning.

Diagram 19 Pruning a young branch to an outward-facing bud.

Larger pruning cuts

Larger cuts are those that need to be made with loppers or a pruning saw. While it is all right for smaller branches to be cut to a bud in the middle of the branch, larger branches should be cut to a junction with another branch, as in Diagram 20, or to the trunk of the tree. The branch that you cut to is known as the replacement branch: this is usually a younger branch that will replace the growth that is being cut. Avoid leaving a stub when cutting larger branches: this stub will either put on new growth in an inappropriate way, or die back.

If you are cutting back to a replacement branch, this should be at least a third of the size of the branch that you are cutting, to ensure that the replacement branch is able to take up the vigour of the main branch. Alternatively, a large branch can be cut back to its origin from the trunk of the tree.

Where it is necessary to cut back to the trunk, trying to remove a branch with just one cut can lead to the weight of the branch tearing the bark on the trunk of the tree. Diagram 21 shows the correct technique for removing a large branch, by making several cuts. Firstly, an undercut should be made about 40cm (1'4") away from the final cut. This cut should be around a third of the way into the branch. This is followed by a downward cut, slightly further away, which will remove the branch without any tearing of the bark. What remains is a small section of branch that can be supported while the final cut is made. This final cut should be just outside the branch collar. Like all pruning cuts, it should leave a clean surface without any tearing or roughness. Any imperfections can be cleaned up with a sharp pruning knife.

Diagram 20 Cutting back to a replacement branch or to the trunk.

Diagram 21 Removing a large branch.

The use of wound paints to protect a cut from disease is now recommended only for the stone fruits – plums, cherries, peaches, nectarines and apricots. See page 140 for more information on wound paints.

Nicking and notching

Although not strictly pruning, nicking and notching are related and useful techniques, used to manipulate the growth habits of individual fruit buds. A small V-shaped piece of wood is removed with a sharp knife, either just above or just below a bud. Late spring is the best time to carry out nicking or notching. These techniques are usually used only on apple and pear trees. They should not be used on stone fruits, because of the danger of introducing silver leaf and bacterial canker.

Nicking-removing a small piece of wood from below a bud-weakens any growth from that bud.

Nicking – removing wood from just below a bud – weakens any growth from that bud. This technique is often used in formative pruning, when removing the leader. Where the leader is removed, there are usually several new shoots, all competing to be the new leader. This results in branches emerging from the trunk at a steep angle, which makes them prone to breaking later in their life. If nicking is carried out below these topmost buds, they will only grow weakly. The following winter, this weak growth can be cut back to the laterals further down that developed at a wider angle as a result of the nicking. Alternatively, unwanted growth can be rubbed out with your fingers, as it grows.

Notching is the process of removing a small piece of wood just above a bud. This encourages growth from that bud. This technique can be useful in formative training, particularly on restricted forms, such as espaliers, where you wish to fill in a gap by encouraging a new branch to grow.

Notching- removing a small piece of wood from just above a bud – encourages strong growth from that bud.

ASSESSING THE TREE

It is tempting to start pruning straight away, but it is vital to spend a few minutes assessing the present condition of the tree and what you hope to achieve by pruning it.

This assessment is the most important stage in pruning. Ask yourself the following questions.

By considering these factors you are building up a picture of the tree and how to correct any problems by pruning.

Formative pruning

Formative pruning is the process of shaping a young tree for the rest of its life. It is vitally important to build up a strong, evenly spaced framework of branches that will serve the tree well in the long term. Although the actual pruning techniques will vary according to the form of tree grown, the principles of formative pruning are shown in Diagram 22 below.

Nearly all tree forms require a certain length of clear trunk before the first branches arise. (The exception is stepovers, but this form is unusual.) Forming this clear trunk involves removing the laterals that form below this point. It is good practice to do this over a two-year period, as illustrated – leaving stubs to grow on for a year helps the trunk to strengthen.

Above the clear trunk, there should be a selection of well-spaced laterals growing at a wide angle to the trunk. Shoots growing at a narrow angle will always be weak, often splitting from the trunk later in the tree’s life, and should be removed.

A young tree will often try to form more than one leader. If a leader is being retained, it is vital that there is only one, otherwise you will be left with a weak point that is likely to split later in the tree’s life. It is best to remove whichever is the weaker, or less upright, of the two leaders. Where a leader is pruned, it is likely that one or more shoots will grow back from buds just underneath this pruning cut. If a replacement leader is desired, the strongest and most upright of these shoots can be retained.

Diagram 22 The principles of formative pruning.

Where two leaders threaten to compete with each other, the weaker, or less upright, of the two should be removed.

The pruning that follows on from this will depend upon the form of tree you desire. During the early years of a tree’s life, the emphasis should be on developing strong growth rather than encouraging fruiting. Although it is fine to allow a few fruits to develop, heavy crops at a young age can cause the tree to become stunted (see Chapter 3, page 42).

Fruit tree forms

There are many different forms of tree that can be used. The most popular ones are described below, together with their suitability for different fruits. Further information about pruning methods for each form can be found in the chapters on individual fruits in Part 3.

The trained forms – espalier, fan, cordon and stepover – are normally grown on the less vigorous rootstocks, because their size is restricted to fit the wall or supporting wires. Most pruning is carried out in the summer, because this encourages weaker growth.

Wall-trained trees need a strong system of support wires. These can either be suspended between wooden posts or fixed against a wall or fence. It is preferable to keep the wires a little way out from walls and fences, in order to increase the air circulation around the tree.

Bush

This is the most common form of tree and one that arises almost by default if little pruning is undertaken. It is suitable for most types of fruit and is easy to maintain. Framework branches emerge from a short trunk (60-90cm [2-3']) to produce an open-centred tree.

Bush

Half standard

This is a similar tree to a bush, but with a longer trunk. The first branches usually emerge about 1.5m (5') from the ground. Half standards can be grown only on the more vigorous rootstocks. They were traditionally grown in orchards grazed by sheep, but are also suitable for specimen trees in gardens. The height of the first branches allows easy mowing underneath.

Half standard

Standard

This is a large tree, suitable for traditional orchards and large gardens. It is a large version of the bush tree, grown on a clear trunk of around 1.8m (6'). It is suitable for all fruit trees that can be grown on vigorous root-stocks, as well as mulberries, which naturally form a large tree. Harvesting and pruning can be difficult on such a large tree, requiring access by ladder or long-handled pruning tools.

Standard

Spindlebush

This is a broad, cone-shaped tree with the leader retained, supported by a tall stake inserted at planting time. Most suited to apples and pears, it is a form that is designed to allow maximum sun to reach all parts of the tree. The spindlebush is an efficient way of growing fruit, but it needs skilful pruning to keep it in shape.

Spindlebush

Pyramid

This form is a more slender cone shape than the spindlebush, and is also supported by a permanent stake. It is usually used for plums, or, in more dwarf form, for apples and pears. Summer pruning can be used to keep the size of the tree small. Again, it is an efficient shape for allowing sunlight to reach all parts of the tree.

Pyramid

Espalier

This is a form of tree with horizontal branches, or arms, suitable for cultivars of apples and pears that form spurs easily. It is a decorative form for growing on a garden wall or creating boundaries in a garden. The number of tiers can be varied to suit the space available and the vigour of the rootstock.

Espalier

Fan

This is a form of tree most suited to the stone fruits (plums, cherries, peaches, nectarines and apricots), as well as figs. It is usually grown against a wall. The short trunk splits into two wide-angled arms, from which the rest of the branches spread. When forming, the middle is filled in last.

Fan

Cordon

The cordon is a fairly upright form of trained tree, most suited to apples and pears. Oblique cordons are most common, because the angle of the trunk encourages heavier fruiting, but upright cordons can be grown, either as a double cordon, or even with three or four arms. Where space is limited, cordons training can enable a number of cultivars to be grown in a small area. The side branches are restricted by summer pruning. A wire framework is needed to support cordons.

Cordon

Stepover

The stepover is usually grown as a decorative edging to a bed. It is suited to spur-bearing apples on more dwarfing rootstocks. The support of wires is needed to hold it in place.

Stepover

ORNATE TREE SHAPES FROM THE PAST

In the eighteenth and nineteenth centuries the French took the training of fruit trees to the level of an art form. All kinds of fancy shapes were created, not because they produced more fruit but because they fitted with the formal, fussy style that was all the rage at that time.

Ever more intricate shapes were produced before the bubble burst at the start of the twentieth century.

An example of the intricately shaped trees that were formed by grafting.

Pruning mature trees

There are several complicated systems of pruning fruit trees, which can serve to perplex the fruit tree grower. Poring over a book, trying to work out which is the fourth bud on a sublateral before making a cut, can be a source of confusion and disillusionment. Fruit tree pruning doesn’t need to be too technical. After all, most people grow fruit trees for fun and to harvest a worthwhile crop – they don’t have the pressure of a commercial grower desperate to achieve the maximum crop from every tree. Although learning to prune can seem daunting, it is worth doing. Once you understand the principles involved, it seems much easier.

A hedge of fruit trees, providing fruit – despite being pruned with a hedgetrimmer!

It is also not worth worrying too much about exact techniques. I have inherited a hedge of apple and pear trees that, due to time pressures, I prune with a hedgetrimmer, and it still provides a worthwhile harvest each year. Follow a few golden rules when pruning and you will not go far wrong.

One system of pruning, known as regulated pruning, is simple enough for the amateur to grasp and effective enough to improve the health and cropping potential of most fruit trees. For this reason regulated pruning is explained in this general chapter on pruning, while its adaptation for particular fruits is covered in the chapters in Part 3. Other types of pruning suited to particular fruits are also covered in those chapters.

Regulated pruning

Regulated pruning is a method that involves opening up the tree to sun and light, renewing growth that has become exhausted and keeping well-spaced branches growing in a radial pattern.

Growth to be considered for pruning out will fall into one of the following categories.

Dead, diseased and damaged wood (sometimes called the 3Ds). Although dead wood might be left on where management for wildlife is important, it is generally good practice to remove it. The removal of diseased wood is important to remove the potential source of infection. The pruning out of diseased wood can take place at any time of year. Examples of diseases controlled by pruning are apple and pear canker and mulberry canker.

Crossing and rubbing branches. Where branches are rubbing against each other, it is likely that the growth is congested, leading to lack of air flow and the increased risk of fungal diseases. Branches hitting each other in strong winds can cause wounds, which are a potential site for spores to lodge and diseases to become established. The photographs below show the thinning out of a congested area of growth on an apple tree. When faced with an extremely dense area of growth, it can be daunting to know where to start – but the only answer really is to start. Once a few cuts have been made, the picture will become clearer.

The wound caused by a broken branch is an ideal place for disease to enter.

Misplaced branches. If viewed from above, a tree would ideally resemble a bicycle wheel, with branches radiating out from a central trunk in a regular pattern. Branches that deviate sharply from this pattern are candidates for removal, as shown in Diagram 23. This particularly applies to branches growing back in towards the centre of the tree. Also in this category are branches that emerge from the trunk in a weak manner, as illustrated in the diagram.

These photos show a congested area of an apple tree, before and after pruning.

Vigorous upright growth. Some trees contain over-vigorous upright branches that emerge from a horizontal branch. These are best removed, because it is preferable to encourage horizontal growth that is more likely to fruit. Vigorous upright growth that emerges from a horizontal branch is also likely to be growing through more desirable branches.

Branches that have become too heavy or long. Such branches are liable to break under the weight of a heavy crop, or in strong winds. These branches will either look too long for the size of tree, move more than might be expected, or bow down under the weight of a heavy crop. There is no need to remove such a branch, especially if it is bearing well; instead, it can be cut back to a replacement branch, as shown in Diagram 24 overleaf.

It is important to be guided by the shape and habit of the tree that you are pruning. Each variety of fruit tree has its own particular growth habit: some will be spreading; others will be upright. Although the principles of pruning are the same, you will not be able to prune both in the same way. Spreading trees can be encouraged to grow in a more upright fashion by pruning to upward-facing buds or growth, while on upright trees it is important to encourage more lateral growth by pruning to outward-facing buds or growth.

Diagram 23 Regulated pruning: removing misplaced growth from a young tree.

Diagram 24 Cutting back to a replacement branch.

Leaning trees

The photograph below shows a leaning fruit tree in need of pruning that will make it more stable. The first thing to ascertain when encountering a leaning tree is whether the cause of the lean can be remedied. Fruit trees are sensitive to light and will often grow away from a tree or building that is causing heavy shade. While removing a building might seem a bit drastic, trees that are causing shade can be reduced in size or crown-thinned, or overgrown hedges can be laid to reduce the shadow cast by them.

A leaning tree. Pruning can help to correct the problem, but this tree has been planted too close to a large tree on its right, so it will always want to grow to the light on the left-hand side.

Diagram 25 Pruning a leaning tree.

Once this has been considered, there are further beneficial effects that can be conferred by pruning. What is needed, unsurprisingly, is to remove some of the weight from the ‘heavy’ side of the tree – usually the one that is receiving more light. It is important, though, to remember that pruning stimulates more growth. If normal pruning was carried out on this side, in a few years the situation could be even worse because pruning encourages growth. Instead, the weight can be removed by making a few major cuts, possibly even removing branches back to the trunk, where regrowth is unlikely. Conversely, it is good to encourage growth on the ‘light’ side (the one with less growth) of the tree. This is achieved by making lots of small pruning cuts, each one encouraging more growth. (See Diagram 25.)

Pruning tools

It is always worth buying good-quality tools if you can afford them. They give better results and last longer. The steel used in the blades will be of better quality, holding a sharp edge for longer. Where you have a choice, it is always worth buying brightly coloured tools that will show up well against a green background.

Brightly coloured tools show up well in grass.

Secateurs

These are used for the smallest cuts, but a good-quality pair will cut surprisingly large stems. In fact, secateurs and a pruning saw should be sufficient for pruning all easy-to-reach branches. There is a choice of bypass or anvil types of secateurs. Bypass secateurs cut rather like scissors, whereas anvil secateurs have a blade that cuts more like a knife on a chopping board. Although this is largely a matter of personal choice, bypass secateurs are usually reckoned to give the best cut. There are also secateurs with such useful innovations as a rotating handle for those with a weak grip, left-handed secateurs and mini-loppers, which will cut thicker stems.

SAFETY

Pruning tools have sharp blades and can pose a risk if not used correctly. But it is actually safer to keep blades sharp, because they will then cut without much effort. You are more likely to have an accident forcing a blunt blade through a branch than by using a sharp blade effectively.

These large secateurs are capable of cutting thicker branches than most.

Loppers

Loppers are useful for cutting thicker stems and for gaining extra reach, since they have longer handles than secateurs. Again, there is a choice of bypass and anvil heads. Many loppers have extendable handles, useful for reaching higher branches. Bear in mind that unless loppers are sharp and well adjusted, they have a tendency to crush branches, leaving a torn cut where disease can enter.

Long-handled loppers

These are useful tools for cutting small branches high up in a tree. There are various types available, the old wooden types having been largely superseded by those with aluminium or fibreglass handles. Those with a small head can be useful in the congested crown of a fruit tree. Some long-handled tools have attachments that enable fruit to be picked high up in a tree.

Pruning with bypass loppers.

Long-handled loppers reaching high into a young tree.

Pruning saw

This is such a commonly used tool when pruning fruit trees that it is worth buying a good-quality one. Modern saws that cut on the pull stroke can be expensive, but are generally worth paying for if you are doing a fair amount of pruning.

Pole saw

When you need to cut higher branches, a pole saw can be invaluable. It is safer to cut high branches with long-handled tools than by accessing the tree with a ladder. On the other hand, a ladder allows you to get closer to the branch that you are cutting, which often enables you to make a cleaner cut.

A sharp pruning saw will produce clean cuts.

Pruning knife

You can use a pruning knife to tidy up any ragged cuts caused by loppers or pruning saws – worthwhile to help prevent disease.

Ladder

A ladder can be useful for reaching into large fruit trees, but it is always worth considering whether this is the safest way to carry out a job. See the box on page 315 about ladder safety. It is possible to buy ladders with a back leg to support them, often advertised for use while pruning hedges. They can be useful for pruning tall trees that are not strong enough to support a ladder. It is also possible to buy ladders with a narrow top, which are designed to fit well between branches.

A pole saw allows you to cut large branches from ground level.

Disinfectant

This can be a useful aid when pruning diseased wood. The blades of pruning tools can be dipped into a bucket of dilute disinfectant (one that is recommended for garden use), or wiped with a rag soaked in disinfectant, especially when moving on to prune a new tree.

Tools should be cleaned and dried after use and sharpened regularly, where appropriate.

QUICK GUIDE TO PRUNING