This section is from the book "The Gardener V3", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
Having disposed of the root-management of Apple-trees on Crab and Paradise stocks, we will now turn to the tops. As we have already indicated, we consider that trees which are to be allowed to attain the greatest development that Apple-trees are capable of, should be on stems a few feet in height. In the case of large trees, which will ultimately wholly occupy the space allowed for them, it is necessary that they should have clear stems 5 or 6 feet high, that room may be afforded underneath their branches for all necessary operations. Where only single rows are grown this is less necessary, and where high winds prevail, it may be an actual evil. In the case of medium-sized trees which are planted singly, or in single rows, trees with stems from 1 to 2 feet will answer well. If trees are to be kept, either by necessity or choice, from becoming more than medium-sized, regular pruning of the branches, both in summer and winter, will be necessary; hence it is desirable that the branches to be operated upon be not elevated unnecessarily.
Whatever form of tree may be adopted, then, trees with short stems should be chosen.
We are somewhat at a loss whether to advise beginners to train their trees in a cup-shaped or pyramidal form. We have seen handsome fruitful trees both ways, and think that we cannot do better than describe both methods, so that, whatever form may be fixed upon, the pruning may be successfully carried out.
Cup-shaped trees are more easily produced than pyramids, for some varieties can only be made to assume the latter form with a good deal of trouble and labour. In the case of young trees a couple of years old or so, with from half-a-dozen to a dozen shoots, the shoots may be so regularly placed that nothing is required but a shortening back of the growths. Strong vigorous shoots need to be shortened back more than half-way, for if left long, the basal half of the shoots will fail to push into growths, and so remain bare, and long bare branches should be guarded against; every portion requires to be clothed with fruit-bearing spurs, and one thing necessary for this is a proper shortening-in of the shoots annually. No two kinds of Apple-trees need the same kind of treatment in this respect. Some kinds are naturally furnished with a profusion of spurs, while others have a tendency to remain bare to a great extent. Those which have a tendency to remain unfurnished, should be shortened further back than those with a different tendency.
Although some trees may be well provided with shoots to form a good foundation for the future tree, the majority will require assistance in this matter. Some may require hard cutting back, in order to induce them to push a sufficient number of shoots. Others may require the centre to be cut out, if the centre should be strong and the side branches weak. In the majority of cases it will be advisable to place a small hoop in the centre of each tree, to which the shoots are to be securely yet loosely tied. At first the shoots should leave the main stem at an angle of something like 45°. Should some of them run away much stronger than the rest, they (the strong ones) should be pinched - that is, have the growing point removed - about midsummer. The weaker ones will then grow stronger and make up lost ground to some extent; and if the practice is persisted in year after year, a proper balance will be established. The pinched shoots will probably push again, but must be repinched, and so restrained from running away with more than their proper share of the sap. The second year they should again be shortened back as before, and the hoop enlarged and moved upwards, and the shoots again properly fastened.
This process should be repeated yearly, until the trees have been brought to assume the desired form. We may say here that the branches should be kept parallel with each other, and about a foot apart, while one tree should not approach nearer to its neighbour than 3 feet. This room is necessary, not only for space required when performing the necessary operations connected with their proper cultivation, but also for the purpose of admitting sun and air, without which success cannot be had.
In pruning such trees in winter, all side-growths from the main branches must be pruned back to one or two buds. In summer all side-shoots should be pinched back, after they have made six or seven leaves, to three, and this must be repeated if necessary. All terminal shoots must be allowed 'to grow on, and not be stopped until the usual shortening-in in winter. Such restriction will naturally tend to the production of fruit-buds in abundance, but not if the trees are over-luxuriant. It is therefore necessary, in almost all cases, to periodically raise the roots and shorten back the strong fibreless ones - in other words, root-prune them, as we have already advised under another head. Only a moderate growth can be fruitful. When weakly, there is not vigour enough to produce quantities of fine fruit. The cure is assistance by means of manuring, as before treated of. When the trees grow rampantly, flower-buds do not form : the cure is their root-pruning and root-lifting. When trees grow moderately and bear freely, neither operation is necessary.
Perhaps we ought to caution beginners against stumping off all annual growth - leaders and everything. Trees which do not or are not allowed to progress within certain limits annually, soon get into a bad way. Restriction, to some extent, can be practised with safety, if a proper balance between top and root be maintained, and even with profit: but when this restriction becomes absolute, either by starvation, root-pruning, or top-pruning, especially the latter, trees (especially small ones) soon get into a bad state. There are scores of trees representing all the modes of absolute restriction to be seen all over the country; we hope these remarks may be the cause of such trees being properly treated in numbers of instances. Absolute restriction has to be adopted inside glass structures, on walls, etc., and Nature herself adopts the plan in the case of full-grown trees; but with trees which have not attained half or quarter their natural dimensions,. or have not filled their places on walls, etc., the case is very different. Most cottagers and villa-owners have to complain that their space is very limited. Land is scarce in this densely-populated and wealthy country, but we presume nobody is restricted from going either upwards or downwards.
Soil may be made any practical depth, and depth of soil, especially in the case of fruit-trees, is nearly as good as width. An acre of ground with 12 inches of soil is nearly worth twice as much as one with only 6, for it will produce twice as much, and land should be valued more in accordance with its capabilities than its extent. Of course 6 inches of soil may be made 12. Indeed we rather think the acre of deeper soil worth more than twice as much of the thinner; for while the labour necessary for two acres of poor soil is twice as great as for one of rich, the produce is often not more - sometimes less. For trees, then, the soil should be made deep, if it is not so to begin with, and then the right thing to do is to let your trees up, up - gradually but steadily up. Gradually, so that the individual branches may have time to grow stout as they grow tall, and so be able to stand beating winds. By this means much of what is wanting in length and breadth may be made up in height and depth.
This is a little of the nature of a digression. The remarks were prompted by the sight of a wall of-fruit trees when every growth made had been snapped off - leaders and all - although two-thirds of the wall was uncovered. Pruning, to some persons, simply means cutting off all annual growth. In many instances no pruning is better by far than this system, which has nothing to recommend it except simplicity. The system is simple.