Pruning is one of the most interesting and fascinating operations connected with horticultural work.A plant is a plastic, responding, changing organism which is affected by everything we do to it. We cannot remove a single branch without affecting the parts which remain. The shortening of any limb modifies to a greater or lesser extent the character which will be assumed by the parts which remain. A plant is capable of being shaped or moulded by pruning, and he who prunes will surely get results. However, as to whether these results are what are to be most desired will have to be learned by experience. One must prune and watch the results over a series of years to learn just what effects any particular treatment will give, as the plant grows.
Pruning cannot be learned from books. It must be learned by studying the habits of plants and the results of pruning. Books on pruning can, however, give one ideas which will enable one more readily to learn how to prune when he comes to do the work.The reading will be helpful only as it guides the operations in the field, and the horticulturist himself must learn directly from the plants themselves.
It is an easy matter to learn how to prune where one has the plants to work upon, and the time to watch their responses to the operations made upon them; but it is a difficult matter to tell others how to prune. No two plants are alike. No two branches are alike. No definite rules can be formulated which will apply to every kind of plant in every locality in which it may be growing. It is a comparatively simple matter to prescribe formulae for the spraying of plants to govern the destruction of insects and control the damages done by fungi. With pruning, however, only systems can be defined which are broad enough to permit of wide modification according to the ideal and desire of the pruner and the habit and character of the plant. This means that the operation must be done in a rational, common sense way, rather than by following prescribed rules.
Since rules cannot be formulated for the pruning of plants, there are certain systems which can be designed that will enable the pruner to so modify his plants that they will all conform to certain well defined types. In grape pruning, for example, there are certain well defined types or systems and in use, such as the spur system, the drooping system and the upright system, with several modifications or combinations of these.In ornamental plants there are natural forms and topiary forms which are made by training the plants into formal or fantastic shapes. In European countries fruit trees are trained into formal shapes,that are used in this country. Some of these differences are due primarily to a matter of taste, while others are employed to suit a certain definite purpose, or to adapt the plant to given surroundings or environment.
In the United States there is a great amount of difference in the style of pruning in the Atlantic coast states and in the far Western states. In the Atlantic coast states the trees are given a high head, while in the Central and far Western states the head is placed closer to the ground. In the Eastern states the trees are trained with a more open head than in the Central or Western states. These styles are due mainly to an attempt to adapt the tree to the climatic conditions in which it is compelled to grow. In the rainy atmosphere of the coast region it is necessary to prune the trees with a high open head so as to admit the sunlight and air, while in the brilliant sunlight and clear dry air of the West it is advisable to have the trees with a more dense head to prevent the tendency to sun-scald.
While there is more or less of difference in the style or system of pruning used in different sections of the country, there are certain well defined principles which will apply to all plants in any climate, or under any system of pruning. Pruning will modify the vigor of plants, and in some ways will cause them to produce larger and bigger fruits. It will keep the plants within bounds and may change the habit from wood producing to fruit producing. Pruning allows the removal of superfluous parts and of injured branches or roots. Intelligent pruning will facilitate the operations of spraying, harvesting and cultivating the orchard, and will enable the operator to train the plant in the form most fitting with his ideal.
In a plant growing normally there is a balance in the relation between the root and top, each supported and nourished by the other: and when either is mutilated the relation is upset and the balance disturbed. Heavy pruning of the top in the dormant season tends to increase the amount of wood growth that will be made the following season. In a contrary way heavy pruning of the roots will result in reducing the amount of wood growth by shutting off the amount of crude food material that is gathered from the soil. Heavy pruning of the top, on the other hand, tends to develop weak portions of the plant by allowing those parts to receive more food. In heavy pruning it is always advisable to remove the weakest parts, as they are usuallly unable to thrive even under better conditions. But since heavy pruning stimulates the production of wood, suckers will be formed, some of which may take the place of the weak parts, and develop into strong branches restoring the plant to its normal shape and habit. The most rational system allows the plant to take its natural form, and this is especially the case with our fruit producing trees. This will vary somewhat with the age of a plant, as when trees are young they tend to a more upright habit than after they reach maturity and have produced several heavy crops of fruit.
One part of a plant may live at the expense of another part. Very vigorous shoots will outgrow surrounding branches because they are better supplied with the crude food material collected by the root and appropriate the elablorated food formed in the leaves of their slower growing neighbors. In trees which have just been grafted the suckers which are formed below the graft will outgrow the branches which arise in the scion, and will outgrow the scion, and cause the starvation and death of the latter. The scion is, in a way, a parasite upon the branch, and the plant tends to throw it off.
The tendency of plants, and young plants especially, is to grow from the uppermost buds. By heading-in this tendency is overcome, and the plants stimulated into developing lateral buds. An obstructionn just above a branch or bud tends to produce strong longitudinal growth in that particular branch, while an obstruction below a bud stops the downward flow of sap and causes a thickening of the parts above. this is often resorted to in the manner of notching or girdling for the purpose of causing the formation of fruit buds or the enlargement of particular specimens of fruit. But these factors are associated with modes of training rather than pruning proper.
When plants are making an excessive amount of wood growth they do not make fruit buds. Checking the growth of the top by pinching or summer pruning will tend to produce fruitfulness.
And while fruit bearing may be to a large extent governed by the methods of pruning the habitual production of fruit is better regulated by small amounts of pruning regularly done, than by heavy pruning at infrequent intervals. In the case of old trees which have been neglected, it may take two or three years after severe pruning before the balance between top and roots can reach and equilibrium and the tree becomes fruitful. Light pruning every year is much better for the trees than heavy pruning done occasionally.
Pruning may be made a means of thinning the fruit by removing the fruit producing wood. In the case of plants which produce their fruit on the long growths of the season before as in peaches, quinces, raspberries, blackberries and grapes, many fruit producing buds will be removed with each branch that is pruned off. In the case of trees that tend to an alternation in the years of fruitfulmess, as in apples and pears, the tendency to alternation may be somewhat overcome through pruning.
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