Fruit Training and Propagation
Why prune at all? Left to themselves fruit trees become over-crowded, diseased and pest-ridden, carrying small fruits on exhausted branches. On the other hand, excessive pruning can lead to too much growth and to light crops of poor quality.
All pruning must have a purpose. There is nothing magical about the process. Experts tend to complicate what should be an essentially common-sense sequence of events. Let us start with objectives:
A fruit tree should be pruned to:
a) admit light and air
b) train the tree to an acceptable shape and size
c) increase the size of the fruit
d) encourage or control growth, whichever the tree demands
e) assist establishment after transplanting
f) remove diseased and broken parts
g) strengthen the branch structure.
Information on pruning is given in the information on individual fruits because each differs somewhat in its requirements.
Let us take the apple tree for our illustration, knowing that other tree fruits may call for rather different treatment.
The young tree
The most common form is the open-centre bush tree. Let us start with a one-year-old maiden tree without side shoots to be pruned in the winter on planting. Roots will have been lost in transplanting. Compensate by pruning severely, leaving some 60cm (2ft). This will encourage the tree to produce strong branches. Four branches, growing at wide angles and evenly spaced round the tree, will be a proper reward in the next season.
At the end of the first growing season these primary branches may be about 45 to 60cm (18 to 24m) in length. In the winter months these should be pruned back by one third, each to an outward pointing bud. This may seem wasteful but it is necessary in order to direct, strengthen and increase the numbers of the branches and their side shoots.
During the next season you will, of course, water, manure, spray and secure the young tree, with the result that the head will have taken shape with perhaps six to eight strong and well-placed branches with a number of side shoots.
The following winter brings a problem. At the end of each primary branch there will be shoots called leaders. Should you prune these? They should be pruned only if it is necessary to achieve one or more of the following objectives:
a) to strengthen the branch
b) to change its direction
c) to provide it with new side shoots
d) to remove diseased or over-crowded branches
If it is necessary to do so for any of these purposes, the leaders should be shortened again by some one third, each to an outward pointing bud.
The side shoots are called laterals. Those growing to the outside may be left unpruned to form fruit buds. Those growing inwards should be pruned back to about 8cm (3m) or removed entirely if there is overcrowding.
At the end of the third growing season, look again at the leaders. Use your previous experience about the extent of cutting back, knowing that weak shoots should be pruned harder than strong shoots.
Follow similar procedures with maiden laterals—leave alone those which are well placed and shorten or remove the others. You must also deal with last year’s maidens, now burgeoning two-year-olds. Leave alone those which are well placed and not competing with the primary branches. Those for which there is no room for further extension should be cut back to the top-most fruit bud. Two-year budded laterals should fruit in the following summer.
The cut-back laterals of an earlier year may be pruned to any obvious fruit bud; if no fruit bud has appeared the extension shoots should be pruned to 2.5cm (1in). Simple rules for straightforward growing Although there are more complicated procedures undertaken by experts, the amateur can content himself with the simple rules mentioned on leaders and laterals. These will suffice amply for apples, pears, plums and Morello cherries as well as for gooseberries and red currants, with only minor variations of scale.
The pruning of raspberries, blackberries and loganberries is straightforward. Remove the fruited canes and the weak tips of the new canes each spring.
Black currants, too, fruit best on the two year wood, but a larger crop can be obtained if some of the older healthy shoots are left.
Generally, the most convenient and successful form of tree is the open-centre bush or the open-centre half-standard or full standard. There is no essential difference between these other than in the length of the stem and the size of the tree.
There is, however, an interesting variant, now popular with the commercial grower, called the central leader tree. The main stem is carried upwards as a central axis for some 2m (6ft 6in) or so. Leader pruning is necessary but care is taken to keep the central stem for a series of central growths. The fruiting branches develop at regular intervals from this central leader instead of originating from a small region of the cutback stem as with the open centre tree. This allows trees to be more closely planted without loss of fruiting wood and is one reason for the popularity of the pyramid, spindle-bush and vertical cordon forms.
The fan-shaped tree, with the branch system trained in two dimensions rather than three, is an effective and attractive means of covering wall space. In the open the palmette shape, adapted from Italian practice, is similar in appearance.
The espalier is a multiple cordon shape, forming horizontal arms in scries on either side of a central axis. There are some splendid examples to be seen in older gardens, but growing branches horizontally in this way is contrary to nature and takes a long time to achieve. The strong vertical shoots which push out from the horizontal arms in response to nature’s dictates tend to be discordant. On the whole the training of espaliers is a task for professionals and dedicated amateurs.
There is no reason why the amateur gardener should not propagate his own black currants, red currants and gooseberry bushes from hard-wood; equally there is no reason why strawberry runners should not be taken, blackberry and loganberry tips layered and raspberry suckers lifted for increase, providing always that the parent plants are healthy. Details are given in the appropriate sections.
Much more tricky is the propagation of tree fruits. In the main these are grown on specially selected rootstocks to which the cultivated varieties (scions) are united by budding or. Occasionally the opportunity arises for the amateur to practise budding or grafting and in any case it is interesting to know something about the techniques involved.
is a form of grafting carried out in July using only a single scion bud. The dormant bud is detached from the maiden shoot, after removing the leaf, by making a shallow slicing cut to produce a shield some 4cm (1-1/2in) in length. Make sure the hard wood at the back of the shield is removed carefully to reveal the bud ‘germ’ before the thin shield is inserted into the bark of the stock by means of a T-shaped cut. The bud, once snugly home in a manner roughly comparable to its original position, is secured by a tie. This is to keep the bud close to the healing cambium tissue so that the scion and stock unite. In the spring the stem of the stock is cut back to the bud, usually in two stages.
For grafting young trees the nurseryman normally uses the whip and tongue graft, involving a scion shoot 15cm (6in) or so in length, which is united to the cut end of the stock in the spring. The tongue is a device to keep the two elements in place. The whole business is no more than a simple piece of joinery designed to bring the cambium layer, the tissue under the bark, into contact so that stock and scion unite, after tying and waxing to aid the process. Plastic strips can be used instead of tie and wax.
The graft inserted in April will start to grow immediately, giving a maiden tree by the end of the summer.
Pruning, training and propagation are based on a simple knowledge of plant behaviour and response and using that knowledge to control the growth and cropping of trees. You have probably met the tree which produces vast quantities of useless timber and little fruit. This may be due to a variety of causes including the following:
a) The rootstock may be too vigorous
b) The variety may naturally be energetic
c) The pruning may have been too severe, the manuring extravagant, or theinherently rich
The remedies include the following:
a) reducing the level of manuring, and especially the nitrogen content
b) grassing down, if feasible
c) confining the winter pruning to the removal of diseased, damaged and overcrowded branches
d) pruning the unwanted laterals in August
e) transplanting, if the tree is young enough
The last is a subtle, beautiful use of applied science. All that is required is the removal in April of a ring of bark, about 1cm (½ in) wide, around the main trunk, covering the wound immediately with masking tape to exclude air. This causes the sudden but temporary suspension of the downward flow of sugars from the green parts of the tree to the roots which, thus deprived of foodstuff, cease their rampant growth. Correspondingly, more sugars are retained in the fruiting parts, helping to induce blossom buds.
The stunted, depressed tree which has ceased to grow calls for different remedies. The owner should:
a) increase the manuring, particularly the nitrogen applications in spring
b) mulch and water liberally
c) remove competitive grass and
d) shorten the leaders and remove any unwanted shoots and suckers
e) stake and tie, to prevent wind rocking.
A pest is a member of the animal kingdom harmful to cultivated plants. This definition embraces a wide range, from tiny organisms invisible to the human eye, such as some mites and eelworms, to the only too obvious rabbits, deer, horses and other mammals. Some birds are pests, although many are beneficial. Most damage to crops is caused by a group of pests known loosely as insects, and often that damage is caused at only one stage of the life cycle, for example, the larva or caterpillar.
Generally speaking the specifics employed against pests are called insecticides – an adequate even if not a strictly accurate term.
Diseases are caused in the main by the invasion of vegetable and related parasites, including fungi and bacteria. Many troubles are caused by viruses, against which there are no chemical controls. As most diseases are nevertheless caused by fungi it is reasonable to refer to the materials used to control them as fungicides. It is difficult to kill one plant, a fungus, living on another plant, and this is one reason why there are fewer fungicides than insecticides.
Much ill-health in plants is caused not by insect attack or fungal invasion but by faults in the environment, or bad nutrition, or poor cultivation—in other words, by bad gardening. As we have to use names to distinguish we call these non-parasitical states of ill-health disorders.
The wrong site, too much or too little water, failure to ensure that the soil is maintained in a fertile state—all these cause more distress to plants in gardens than do. The first step in pest and disease control must be to grow good plants.
We should not overlook weeds, which can be defined as plants in the wrong place. A rose in a potato field is a weed; so is a potato plant in die. Grasses are splendid in but undesirable among the . Materials used to control weeds are called .
Why not let nature have her way? There is a school of thought which holds that nature, left alone, produces a balance in which predators and parasites keep insect and similar pests in check. One never sees the same argument applied to weeds, which only too readily overcome our cultivated plants if left alone. It is not really possible under the artificial conditions in which we live to leave the safeguarding of our crops entirely to nature. It is necessary for the gardener to work with nature if he wishes to obtain the best results.