Pruning is best described as a horticultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots. This may be done for a number of reasons, with the method and timing being of some importance, particularly when flowering and fruiting plants are the subjects – and we wish to achieve a good yield of high-quality produce.
The main principles of pruning
When we prune, there are a few basic objectives to achieve healthy plants, which will then reward us crops for as many years.
Firstly we need to remove growth that is dead. Once plant cells have died, they cannot fight infection, so they are an entry point for diseases to enter. Cankers, Coral spot, and Silver-leaf are all diseases of fruit trees and bushes which could gain entry through dead wood, which should be cut out, back to a suitable place in good, healthy growth.
Growth that has already become diseased also needs to be removed. Plant diseases will spread through the plant and may eventually cause death. Pruning should remove infected wood by cutting back to healthy growth to help prevent its spread both through that plant and also to neighboring fruit trees and bushes.
Fungal diseases, such as Apple and Pear Canker and Coral Spot, can usually be controlled by good pruning, but Bacterial diseases such as Bacterial canker (plums and cherries) and Fireblight will colonize the plant cells far more quickly and will usually necessitate the whole tree being removed to help prevent spread.
Damaged shoots and branches are more prone to infection by diseases, which can then spread. This can include damage to the trunk by rabbits or deer, particularly in the winter, which is why guards are so important when planting. Branches of fruit trees and shrubs may also break when carrying heavy crops, especially in windy conditions. A good, clean cut is far less likely to become infected with a disease than a torn off limb.
Pruning, particularly of fruit, will also aim growth which is generally termed as displaced. Branches or shoots that are ‘in the wrong place’, such as crossing or rubbing, should be removed as these are more prone to damage and infection. Removing these, as well as other congested, surplus, growth, helps airflow and the general health of the plant. Letting more light in will ensure better quality produce and help improve the color of the fruit.
The basic rules of pruning fruit trees and bushes
Here are the basic rules you need to learn for pruning your trees:
Use sharp tools, secateurs, loppers, or saws, depending on the size of wood being cut. Do not overstress your hands or your tools!
Generally, do not remove more than one-quarter of the living growth as this can encourage too much vegetative, nonflowering growth the following year. This could then lead to a biennial bearing pattern in fruit trees, where you get a large crop of (usually small) fruit one year and none the next.
Start by pruning out material that is dead, diseased, damaged, and displaced, such as crossing or rubbing, wood as described earlier. Then consider your basic required framework, and work to that.
Always prune back to a suitable point, just above a ‘node’ – which is where there are leaves, or leaf-scars, or a new shoot. When removing branches, cut at an angle and leave a collar that will heal over and prevent damage to the main trunk.
If you wish to remove branches from the lower parts of trees in order to leave a clean trunk: do not prune up more than 1/3 of the tree’s total height. The lower branches help promote trunk calliper growth and are very important in the early years.
Timing of pruning is important in helping to maximize yield as well as prevent diseases such as Bacterial Canker and Silver Leaf (plums) from entering the plant through wounds or pruning cuts. Members of the Prunus genus (plums, cherries, peaches, etc.) should be pruned from mid Spring to Summer – never in the winter when wet and windy conditions encourage the spread of these diseases
FORMATIVE PRUNING is required on young plants to create vigor and to build a basic framework. Fruit trees and shrubs, in particular, benefit from formative pruning when they are first planted, as energy is not then wasted on unrequired growth, which has to be cut out later.
MAINTENANCE PRUNING is the regular, usually once-a-year, prune to enhance the flowering and fruiting, i.e., the yield, of our fruit trees and shrubs as well as improving the actual quality, such as size and color, of the resulting crop. Regular maintenance pruning will help ensure the balance of vegetative and fruiting wood and help prolong the life of the plant.
The timing of maintenance pruning will vary depending on the type of plant, but here is a quick guide to the major tree fruits.
Apples and Pears
Apple and pear trees trained as free-standing bushes are best pruned every winter. This becomes somehow mandatory to ensure a good cycle of fruiting wood. In general, the trees that are not pruned become less productive and congested with old branches.
The general aim is usually to create an open goblet shape with a framework of four to five main branches. Apples and pears, however, lend themselves to many other pruning and training forms, including Pyramids, Espaliers, Cordons, Fans, and Step-overs which are both decorative and allow for increased productivity in a limited space. These restricted forms rely on summer as well as winter pruning.
When to winter prune apples and pears
Pruning should be carried out when the tree is dormant, between leaf fall and bud burst. This is generally between November and early March. The more vigorous the tree, the later it may be left.
Shorten the previous year’s growth on each main branch (primary) by about one-third to a bud facing in the required direction. This will encourage the development of new branches and spurs and maintain a good shape.
Leave young laterals (side-shoots) unpruned so they can develop fruit buds in the second year.
Only remove the young laterals if they are crossing or if the growth is too crowded, i.e., growing closer than 4-6 inches at the base.
Remove strong shoots, more than 6 inches long, growing towards the center of the tree.
For older trees, remove or thin out any spur systems that have become congested. Where thinning ‘or’ removal is required, remove spurs on the underside of the branches, where the developing fruit will not receive enough light and produces inferior fruit.
If your apple tree is a tip – or partial tip-bearer, cut back a proportion of older fruited branches to a strong younger shoot positioned closer to the main trunk or higher up the branch. This will reduce congestion and prevent branches from becoming too long.
REGENERATIVE PRUNING may be required on trees where regular maintenance pruning has not taken place, or the plant is getting too large for its allocated space. Note: consider rootstock choice for the eventual size of the tree when buying all fruit trees
Open the center of the tree by removing larger branches at point of origin with a sharp pruning saw. If several large branches need to be removed, spread the work over two or three winters as very hard pruning encourages even more vigorous regrowth.
Reduce the height and spread of any branches that have grown too large by cutting them back to a strong outward and upward facing lower side branch (making sure this lower branch is at least one-third of the diameter of the branch being removed).
If the tree is very vigorous, sending out an excessive amount of growth each year, consider also carrying out some pruning in summer (mid-August – late September). Summer pruning depletes the tree’s resources and will help reduce strength. Prune the longest laterals (side shoots) longer than 10 inches back to about 6 inches all over the tree to encourage fruit bud formation.
Plum and other stone fruit (cherries, peaches, apricots) trees do not require as precise pruning as apples and pears but still benefit from initial training and the thinning of old wood to ensure they produce as much fruit as possible.
Most plums and cherries are grown as open-centered trees, known as bush pruning, but may also be trained as pyramids, fans, or cordons. Peaches and Apricots are commonly grown against walls for extra protection as well as for decorative merits.
When you should prune plums
Avoid pruning plum trees in winter since it increases the risk of infection by silver leaf disease, a disease to which plums and other Prunus species are prone. The recommended time for pruning is usually spring (April) for young trees and mid-summer (July) for established ones.
The bush is perhaps the most popular method of training and pruning and creates an open-centered tree with a clear stem of around 30-35 inches. The ultimate size of the bush will depend on the rootstock it is grown on – for example, plums grafted onto ‘Pixy’ rootstocks will reach around 9 feet, ‘St. Julien A’ 12 feet and ‘Brompton’ and ‘Myrobalan B’ up to 19 feet.
The goal of pruning is to create an open-centered tree. This begins with efficient formative pruning in the spring after planting.
On established trees, rub out any buds developing on the lower trunk and carefully pull off suckers arising from the rootstock. Pruning is mostly limited to removing crossing, weak, vertical and diseased material. If the plum tree is still crowded, then further thinning can be done in July.
Controlling vigor of Plum trees
The tying down of young, flexible branches to the horizontal can reduce excess vigor and encourage fruiting. This technique is known as festooning and is best done in the summer. It can prevent trees from becoming overgrown and is also effective for both bush and pyramid plums.
Ties are left in place until the branch stays naturally at the new position, usually the following spring. Attach one end of the tie to the branch tip and the other end to a stake or the trunk.
REGENERATIVE PRUNING may be required on neglected and overgrown bush trees.
Rejuvenating an old, neglected plum tree should be staged over several years. The aim is for a well-balanced tree, keeping the center of the crown free from shoots to allow good light penetration.
Trees usually respond to larger pruning cuts by sending up a mass of new shoots – these will need to be thinned in the summer to leave just one or two.
This article was submitted by Jason N Clark.