How to Prune Plum, Cherry and Peach Trees
PRUNING RISKS FOR PLUMS
Second only in popularity to apples, a freshly picked plum is one of summer’s finest treats. Damsons and gages, which are close relatives of the plum, have the samerequirements. Plum pruning is not without risk – to the tree. The of silver leaf fungus disease may gain entry through pruning cuts, and this disease is capable of killing a tree. As the name implies, leaves on affected branches take on a silvery appearance by comparison with healthy leaves.
Suspect the disease if you see much dead wood in a plum tree. If towards the end of the year small bracket fungi are produced on the dead wood it is almost certain that silver leaf is the cause. For confirmation cut into suspected wood and look for a dark ring staining the wood; this is a sure sign that the fungus is present.
First action with an established plum or gage tree in the garden is to cut all dead branches back to healthy wood, preferably by midsummer. If they prove to be silver leaf infected, cut back until no stain can be seen in the wood. Then paint the cut surfaces with a pruning compound, and burn the prunings immediately.
Because of the risk of introducing this disease, all bush, half-standard or standard plum trees should be pruned as little as possible. What pruning is necessary should be carried out in early summer when the cuts heal rapidly and silver leaf infection is least likely. All that is required is to remove crossing branches that may rub together and a few others that may be crowding the centre of the tree. Some varieties have a pendulous habit and the tips of a few branches may have to be cut back. Plums fruit on wood produced in the previous year and on spurs on older branches. If pruning in early summer means the removal of branches bearing unripe plums, the operation can be delayed until immediately after picking.
Plums are particularly prone to branch splitting, especially if the crop is heavy, and it is wise to have some props handy to support laden branches in a good year. However, if the worst happens, remove the broken branch at once and cover all damaged surfaces with wound paint.
ESTABLISHMENT OF A BUSH PLUM
In the average garden a bush plum, with 60-90 cm (2-3 ft) of trunk before the branches begin, is the best shape. Half-standards, with a 1.2 m (4 ft) trunk, are useful for the more spreading varieties such as the popular Victoria. Plums are not suitable for growing in restricted forms such as cordon or espalier.
Nurserymen will supply one-year-old trees (maidens) or older trees on which a framework of branches has already been formed. If a two-to three-year-old tree is purchased, no pruning will be required until the spring a year after planting. To produce a bush tree from a maiden, the stem must be cut back to just above as a bud, about 23 cm (9 in) above the desired position of the lowest branch. This is done after planting, in the spring and before bud burst. Small shoots low on the stem can be left, as they help to build up the tree until a number of strong branches have been formed. In summer shorten them back to four or five leaves, and after two to three years remove them.
Pruning in the second year involves the selection of the main branches. A number of strong shoots should have formed near the head of the tree, and about four of similar strength and evenly spaced round the stem are selected. These young branches ideally should make an angle as near as possible to 90° with the main stem. Such branches will be able to support a heavy weight of fruit, while those emerging at a narrow angle will be weak and prone to split. The chosen wide-angled branches are cut back in spring to a bud about halfway along their length while the remainder which form narrow angles and are badly placed are removed entirely.
In the third year, leaders (strong-growing branches) are cut back by half the growth they made in the previous year, and crossing and crowded shoots are removed. In subsequent years pruning is carried out in early to mid-summer and only involves the removal of dead, broken, crossing and crowded shoots as already mentioned.
There are two distinct types of cherry: the sweet or dessert kind, and the acid cherry, of which the popular ‘Morello’ is perhaps the most widely available. With neither of them is winter pruning carried out, owing to the risk of silver leaf disease infection.
Only in recent years has it become sensible to recommend growing sweet cherries in smaller gardens, because no dwarfing rootstock was available, and consequently they grew into large trees. Most today are propagated on the new rootstock Colt, which restricts the natural vigour of cherry trees. They can now be grown as a traditional ‘fan’ against a 1.8-2.4 m (6-8 ft) wide wall, or in the open as a pyramid where the height can be restricted to about 2.7 m (9 ft). With trees of these proportions it is easy to net against marauding birds, something that posed a problem with the larger trees. Further, in the past, two varieties needed to be planted to ensure cross pollination and adequate fruiting. Now there is the excellent variety ‘Stella’, with large dark red fruits ready for picking in mid-summer.
The tree is built up in the same way as the peach. Sweet cherries are pruned as little as possible once the framework is formed. Cut side shoots (laterals) back to five or six leaves in summer, then shorten these again to three or four leaves in autumn. Where fan-trained trees are concerned, rub out shoots that appear on the wall side of the branches as soon as possible, while they are small. Branch tips (leaders) are not pruned until they reach the top of the wall when they are bent over the tied down for a year. This will weaken them and encourage new shoots to break so that the following autumn the leaders can be cut back to replacement laterals. Also dead wood is removed and strong vertical shoots cut out, or tied down horizontally (which will weaken them) if they are needed to fill a gap.
Bush or fan trees can be planted in the garden about 4.5 m (15 ft) apart. They are more or less self-fertile and a single tree will set a good crop. The framework of bush trees is built up in the same way as for plums. Acid cherries fruit mainly on wood produced in the previous year, so once the framework of the tree has been formed subsequent pruning is aimed at encouraging this wood.
These cherries will make fresh growth from dormant buds in old wood, so each year a few branches are cut back to two-year-old wood in the case of young trees (about four or five years old), and into three-and four-year-old wood in the case of older trees. This is best done in spring after buds have burst. Diseased and dead wood is also removed, as well as inward and crossing branches to keep the head thinned out. Once again, paint large cuts with pruning wound dressing to prevent silver leaf infection.
Fan-shaped trees are built up in the same way as for peaches, except that only 8-10 cm (3-4 in) is left between the side shoots. Once the tree is established a few of the older branches are cut back each year to encourage a supply of young shoots which are tied in 8-10 cm (3-4 in), apart in winter. Otherwise treatment is the same as for peaches.
Peaches flower early and the danger is that the blossom is sometimes killed by frost, with consequent loss of fruit. To obtain some protection they are often grown trained in a fan-shape against a south-or west-facing wall. However, in a relatively frost-free situation free-standing trees can be grown with fair prospect of fruit.
Training a free-standing bush is easy enough. When a one-year-old (a maiden) is planted, it is cut back late in the following spring to a suitable side shoot (lateral) 45-60 cm (18-24 in) from the ground. Side shoots lower down the stem are removed entirely. In the following year there will be further side shoots which will compose the framework of branches. Cut these back by about one-third to an outward-facing bud. Shoots growing into the centre of the tree are removed and dead tips are cut back to a live bud.
The aim is to have branches arranged as evenly as possible in a spiral round the main stem. In subsequent years what pruning is necessary is carried out in spring. It is only necessary to tip-prune any shoots that have died back and to remove branches that are crossing others or crowding the centre of the tree. When old branches get pulled down to the ground by weight of fruit they are cut back in spring to a strong-growing vertical lateral.
Trees are planted 23 cm (9 in) away from a wall and the branches are tied to horizontal wires spaced about 15 cm (6 in) apart so that they radiate like the spokes of a wheel. After planting in early spring a maiden tree is cut back to 60 cm (24 in) from the ground. As shoots start to extend, one is left at the top plus a pair 20-23 cm (8-9 in) above the ground and close together but on opposite sides of the stem. The other buds are rubbed out with the thumb. The two lower shoots are encouraged to grow along bamboo canes fixed to the wires and radiating out from the stem at an angle of 45°.
When the shoots are about 45 cm (18 in) long the main stem above them is carefully cut out. If one shoot tends to grow more strongly than the other it must be brought down to a more horizontal position, which will restrain it.
In the second winter the two shoots are tied down to an even more horizontal position and cut back to about 4.5 cm (18 in). In the second summer a shoot at the end of each branch is allowed to grow along a cane to continue the growth ol the main branch. Two shoots on the upper side of each branch ‘are also allowed to grow, plus one on the lower side of each branch, and these are also tied to canes fixed to the wires. All other buds are rubbed out as soon as they can be handled.
In the third winter each new shoot is cut back by about one-third to a growth bud, on the upper side of the shoot if possible. Growth buds can be recognised because they are slender, while fruit buds are fat. If in doubt always cut to a triple bud cluster as these invariably consist of two fruit buds and one growth bud.
If there is space for a large tree, the treatment carried out in the second summer can be repeated once more, but otherwise steps are taken to secure a crop. To this end, third-summer treatment involves allowing the bud at the end of each of the eight branches to grow on, tying them to canes or directly to the wires. Rub out shoots that grow directly towards or away from the wall. Shoots from the remaining buds on both sides of the branch are kept where they can be spaced about 15 cm (6 in) apart, and excess buds are rubbed out.
Once the shoots have grown to about 45 cm (18 in) the tips are pinched out. They are tied to the wires so they are spaced 10-15 cm (4—6 in) apart. These shoots should bear fruit the following year.
Fourth and subsequent summers require the removal of superfluous shoots, the pinching back of shoot tips and the tying-in of new shoots that will bear fruit in the following year.