Many people feel uneasy about pruning their trees. This is very understandable: it would be easier to prune if one knew in advance how the tree you would like to prune will react to it. one thing is certain: irrespective of age or shape, the tree will undoubtedly react to pruning, and the way it reacts depends on the way pruning is carried out. In my view it is very important to recognise that there are some basic principles, but once these principles are understood, pruning becomes a very interesting activity, and your skill levels will increase very rapidly, so that you can perform this work successfully and to good effect.
Firstly it is important to place the main types of fruit trees into separate groups. Each group reacts differently, in various ways, to the timing and method of pruning.
Group 1: Apples and Pears, also called ”top fruit”
Group 2: Plums, Greengages, Sweet Cherries and Sour Cherries, the “stone fruits”
Group 3: Peaches, Nectarines and Apricots, also stone fruits
Group 4: Soft fruits; Red Currant, Black Currant, Gooseberries, various Berries
Group 5: Quinces, Medlars, Crab Apples
Group 6: Cobnuts, Walnuts and Sweet Chestnuts, Mulberry trees
Group 7: Vines
Group 8: Others, such as figs
Secondly, one needs to be fully aware of the occurrence of the annual growth cycle of fruit trees and fruiting plants. First, let us look at the growth cycle of fruit trees. Fruit trees can reach a high age and display a certain rhythm of different growth patterns each year. It is very important to understand the logical stages of growth development. Let me explain.
When winter has passed and early signs of spring have arrived, the fruit trees are beginning to wake up from their long winter sleep, officially known as the “dormant period.” Therefore when dormancy is coming to an end, the first growth cycle begins. The end of the dormancy phase is usually at different times for the various tree groups; the trees of Group 3 wake up first, around the end of February. Group 2 around the middle of March, Group 1 around the end of March. There are no set dates as such. Sometimes the season is early, sometimes late, mainly influenced by the preceding weather patterns and in particular the temperature.
How does the first growth cycle start? You only have to look closely at the trees and you will notice that the swelling of the fruit buds is on the way. This then is followed by a period of flowering. When that stage is completed and the petals are beginning to drop, new shoot growth is rapidly on the increase. This may continue well into August. The exact timing of cessation of growth is dependent on the age of the tree, availability of moisture and the crop load. But as a general principle, we need to acknowledge that by the end of August the growing and extension and formation of new shoots and laterals is coming to an end. It is at that stage that the tree is in the process of completing the growing of its fruits and at the same time, it is already beginning to prepare for dormancy. This final part of the growth cycle will have ended when, after the crop has been harvested, the tree’s assimilated surplus is stored away in the root system. As a result of this, the leaf quality gradually deteriorates, and finally by the end of November, all the leaves have fallen and the tree is fully dormant again.
Now, when one fully understands this behaviour of fruit trees, we have a solid basis on which to decide exactly how to slot our aims regarding tree control and maintenance into this overall process. By tree control, I mean to the ability of shaping the tree in such a way that it fits the area or space available. However we can only begin to talk about pruning as “mission accomplished” if, as well as controlling tree size and shape, we also succeed in maintaining satisfactory, regular, annual cropping, with good quality fruits.
Controlling tree growth
The question arises: how can we influence the tree’s performance? Sometimes, it may not even be necessary. There are just as many people with large gardens as small gardens. People with large areas to fill have a different set of requirements. Some are not really interested in the crops of the trees. Many just need the trees to blot out some offensive office block or such like. Let’s look at some of the different cases.
When we want a large tree
How can one influence tree growth, if we have plenty of room and therefore have as a priority, the rapid expansion of tree volume? In this case we must make sure the trees have been budded or grafted onto a semi vigorous or a vigorous rootstock. The rootstock MM106 is in most cases the right choice. However strong the rootstock, if the young trees have to fight against a dense cover of weeds and grass, then in many cases the tree’s performance is held back. Too much energy is wasted battling with the weeds to find enough moisture to achieve rapid growth. Without sufficient soil moisture, growth comes to a complete stand still. The same applies if livestock is allowed to push the trees about and thereby loosen the roots, due to the absence of adequately strong and tall enough tree guards. Another increasing problem due to high levels of unemployment is youth vandalism. In that case it is essential that the tree guards are of such a construction and design, to form an effective barrier to protect the trees and its main framework of branches from being vandalised.
The other aspect is nutrition. Strong tree growth is hampered if nitrogen is not readily available. In advance of the planting of the trees, a good supply of well rotted farmyard manure should be incorporated in the soil.
Then finally, some varieties are so fertile that it is difficult to stop them cropping in the second year. A small token crop of fruit is no problem. If however the tree is loaded with fruit, then shoot growth will suffer as too much energy has gone towards fruit production. The best way of overcoming this problem, apart from fruit thinning, is to prune back the young shoots during the winter months by a third. Also, the variety choice is important; some varieties by nature make a big tree, other varieties by nature only make a smallish tree when mature.
So, what about if we don’t have lots of room and still like to achieve regular cropping?
Most people would like, more than anything else, to achieve regular crops of good fruit. Can one influence the fruit set and the overall crop of fruit on an annual basis? Yes, we can. Fruit set is dependent on a variety of factors;
1) the site; height above sea level, height in relation to the immediate surroundings, the micro climate of the site.
2) the weather conditions during the blossom period
4) balance between shoot growth and fruit growth
5) the crop volume of the tree during the previous year
6) the time of harvesting
7) the genetic make-up of the variety
8) the angle of the branch carrying the fruit bud, in relation to the vertical trunk of the tree
9) the overall nutritional status of the soil
10) the position of the branch as regards light intensity
This, I realize, is quite a list. However if one is interested in the subject of growing fruit, a lot of those points are plain common sense. At a later time I will come back to these points and go more into the details of the various points. For now I would like to come to some straightforward recommendations.
Treatment of young, over-vigorous trees
1) Bring them into cropping by not pruning in, except for the leader
2) Tie branches down; high branches under the leader slightly below horizontal, in the middle of the tree horizontal, in the bottom of the tree slightly upwards
3) Have fairly wide grass strips down the middle of the alleyways
4) Do not use any fertiliser or organic feed, until cropping has become established.
Treatment of youg, under-vigorous trees
1) Cut into the one year old shoots
2) Prune early in the winter
3) Tie up essential framework branches, where necessary
4) Make sure the trees are not short of water
5) Don’t overburden the tree with lots of fruit
6) Use a straw mulch where possible.
Treatment of trees that have gone out of hand
1) Prune the trees as soon as picking has been completed
2) Maintain thick branches in the bottom of the trees
3) Cut out all thick branches in the top of the tree
4) Restore a triangular shape to the canopy of the tree
5) The following winter, do not prune at all
6) Encourage the tree to crop, as outlined above
Winter pruning and summer pruning
Pruning can be divided into two groups according to the time of year: winter pruning and summer pruning. The effects of each differs according to the age of the tree. Here is a scheme detailing the principal effects of winter and summer pruning on young and older trees:
A. In young trees:
Winter pruning (less than 8 years old):
1. Winter pruning stimulates more growth
2. Winter pruning reduces cropping
3. Winter pruning stimulates root growth
4. Winter pruning produces larger trees
1. Essential tool for containment of tree size
2. Essential for extra fruit bud formation
3. Essential for diverting energy to fruit growth
4. Essential for regular cropping
B. In older trees (8 years and older)
1. Winter pruning encourages essential replacement shoots
2. Winter pruning regulates crop yield and fruit size
3. Winter pruning strengthens root systems
4. Winter pruning maintains desired tree size
1. Essential to keep tree structure open to sunlight
2. Essential to avoid overcropping
3. Essential to create healthy spurs and dards
4. Essential to maintain tree vitality