By: Jonathan Sturm
Growing apple or pears to cosmetic perfection by the organic method is difficult. Like all members of the rose family (Rosaceae), they are subject to the disease, black spot. To minimise the complaint, as in all organic growing, the key is to provide as near perfect growing conditions as possible. Minimal damage by the fungus is a cosmetic problem on the fruit only. Allowed to get out of control, it can severely damage the leaves, leading to stunted, weakened growth.
Apples require fairly good drainage. Ground that lies too wet over winter may stunt, or even kill trees. Where this problem is likely, as in heavy clay soils, trees must be grown on mounds or a ridge. Pears tolerate poor drainage better than apples. Heavy soils provided with adequate levels of good compost humus drain much more freely, as well as strengthening the trees' disease resistance. Excessive nitrogenous fertiliser must be avoided at all costs, as this leads to excessive foliage at the expense of fruit and fruit quality. Apples and pears both grow well in sandy soil through to medium clays.
As frost can damage the flowers, the site needs to be frost free by flowering time. This is early spring for pears and mid spring for apples.
Too much wind damages the trees severely. Limb rubbed fruit is obviously unattractive. Root damage can be caused by the trees swaying in severe winds. Dwarfing root-stocks have brittle roots and consequently need trellising or other support, even in sheltered positions.
Warm, sunny sites are ideal, but apple and pear trees tolerate partial shade. The main consideration here is the necessity for sunlight to colour the red varieties. Green apples, such as Granny Smith, have less need for sunlight than Red Delicious. Red apples require cool, dewy mornings to colour up well. Dew appears to amplify the effect of the sun.
Spread ample supplies of partially decomposed compost around the drip-line. That is, keep the compost away from the trunk. There are no feeder roots there. Cover the compost with a mulch of hay, straw, leaves or hardwood sawdust and keep this away from the trunk, too. Trapping excessive moisture adjacent to the trunk can cause rotting of the bark. Top-dress sawdust with lime or dolomite. This will reduce the effects of substances in the sawdust that inhibit growth. You will often be told that sawdust should not be used as it robs nitrogen from the soil. This is true only if you dig it in and/or fail to provide ample compost. Ample compost is the amount required to cover the ground under the drip line to a depth of 25 mm. Adjust the amount of compost if growth is too vigorous or too weak. Compost is a variable fertiliser and requires you to observe the effects your particular recipe has.
Foliar feeds of fish emulsion and liquid seaweed are greatly appreciated by the trees. Commercial preparations of seaweed such as Maxicrop can be less useful than the home made variety, as these often contain too much urea. (See Liquid Fertilisers)
Growing a grass sward between the trees that contains a variety of herbs is beneficial. Clover should be a main constituent, as it fixes atmospheric nitrogen that is released to the trees when it is mowed.
Pruning Apple and Pear Trees
Allowed to grow untrained, fruit trees would rapidly become thickets, the fruit hard to reach and small. With little light penetrating the tree, red varieties of apple would not colour. The reduction of sunlight also increases the incidence of fungal disease. Pest and disease controlling sprays would not reach all parts of the tree. Pruning then has a multiple purpose. There are two trends in modern pruning that differ from the old ways. Trees are kept more compact and old wood is removed to allow the tree to renew itself.
Pruning implements should be the best you can afford. You will need no more than a stout, very sharp knife for very young trees. Knives make cuts that heal much quicker than cuts made with the secateurs. Secateurs have a crushing effect as well as making a cut. Their benefit is that they need only one hand to use. For removing large branches, a pruning saw is best. It has coarse teeth for rapid sawing.
Pruning in summer reduces vigour, promoting the formation of fruit buds for the following season. The pruning cuts also heal much faster. The main reason for pruning in winter is that the winter is a less busy time than summer. The old idea of painting pruning cuts has fallen out of favour. The paint merely seals in the disease causing organisms where they are protected.
Pruning heavily encourages growth of wood in the following season. Light pruning is used on trees making vigorous growth. Pruning too heavily will prevent fruiting, even on a tree well furnished with fruit buds. The use of heavy pruning to promote shoot growth is less satisfactory than the use of manure or water or whatever else is in short supply and that is reducing vigour.
There are three main methods of training apple and pear trees for the back yard or small orchard, the spindle bush, the pillar and palmette. The first two are freestanding and the latter needs a trellis. There are also two sorts of apple trees, spur bearing and tip bearing. Tip bearers are more vigorous and you should be careful not to remove the laterals with the fruit bud at the tip. Pruning tip bearers leans toward removal of larger branches, allowing the branch to regrow. Spur bearers are less vigorous and require less pruning. Pears are all spur bearers and grow into larger trees than modern dwarf apple trees.
The shaping of apple and pear trees is normally done in winter and so is called winter pruning. There are many methods of pruning apple and pear trees and several methods are covered below. This pruning can be done in late summer or autumn with advantage. This timing curbs excess vigour and the pruning cuts heal much quicker. Cuts made in winter generally give rise to vigorous growth, often at the expense of fruit.
The Spindle Bush
The spindle bush has a vertical central stem and the branches are longest at the base and pruned shorter toward the top, giving the tree a characteristic pyramid shape. The branches are kept at an angle of from 45 to 90 degrees from the stem. This is achieved by using wire twiggers, wooden spreaders or tying down until the angles are set. The young tree should be well feathered, that is be furnished with several lateral shoots off the main stem. After planting out, the central stem should be shortened to leave it 30-40 cm long. Other leaders are shortened by about one third. Individual buds can be treated as below, to encourage the formation of branches in appropriate places. In general, branches should not overlap at a distance of less than 60 cm apart. If your variety is prone to bare wood (buds are a long way apart) the pruning should be more severe.
This is continued each year until the tree approaches the height you wish it to attain. Pruning thereafter consists of removing crossing laterals and removing very old branches to allow new branches to form and take their place.
The pillar tree takes renewal to an extreme. Again there is a central erect stem, but there are no branches. Laterals are allowed to form and grow through to the fruiting stage in their third year. They are then removed to within 8-15 cm of the stem and the process repeated. Pruning must be organised to allow the stem to be furnished with an equal quantity of maiden, two and three-year wood. To achieve this, half the maiden laterals need to be shortened on the new extension growth. As with the dwarf pyramid, the extension is shortened according to vigour and buds treated to encourage the growth of shoots.
On the two-year-old portion of the stem, one third of the laterals will need shortening. On three year or older stems, pruning consists of removing only three-year-old laterals that have fruited once (or twice with some varieties). In the second and third years, laterals will have extension growth. This should be removed in summer. During the winter, the lateral can be shortened as a method of thinning off fruit in advance for heavy bearing trees.
While pillar pruned trees take some effort to establish, they are the easiest to maintain.
The palmette is grown against a trellis, using wires to obtain the 45-degree branch angles required to promote heavy fruit bud formation. Treatment is very similar to the spindle bush, except the laterals are more severely shortened to encourage permanent spur formation. It is a method most commonly used where space is at a premium, the trellis often being attached to a wall.
Bud Notching and Nicking
Removing a small portion of wood above a bud encourages the growth of a shoot from that bud. Removing a portion of wood below a bud prevents the formation of a shoot.
Bark Removal and Root Pruning
Where trees are reluctant to fruit due to excess vigour, there are two methods to induce fruiting. Remove a portion of bark or cut through a main root, as in the illustrations. The latter has the undesirable side effect of reducing the tree's anchorage in the soil with the possibility of it blowing over in a gale.
Summer pruning is carried out for two reasons; to curb excess vigour and to allow sunlight to reach red varieties, so that they will colour. The new season's growth is cut away, hard if vigour is a problem, lightly where stronger growth is needed. Cutting away the leaves shading the fruit so that it colours properly is called leafing.
Apples and pears will set many fruits to the bud. Left to mature, they will remain small and some will drop and be wasted. When the fruit is still relatively small, about the size of a walnut, remove all but one fruit from each bud. The average spacing between fruits on the limb should be about 150 mm. Where codling moth is a problem, remove the affected fruit first and compost the fruit, rather than letting it just fall to the ground.
Pest and Disease Control
Codling moth is the most destructive pest of apples and pears. The grub enters the fruit shortly after it hatches from the egg. Consequently, no amount of spraying with other than systemic pesticides is going to help. Minimise your problems by practising orchard hygiene. Do not allow fallen fruit to lie on the ground. Running chooks will help as they will readily devour windfalls and the grubs they contain are an unlooked for windfall for the chooks.
Bandaging the trunk of the tree with hessian or corrugated cardboard in December will reduce moth populations drastically. Examine the bandage fairly regularly until early autumn and destroy the cocoons by immersing the bandage in boiling water or by burning. Replace the bandage each time, leaving the last in place until midwinter.
In southern Tasmania at least, codling moth infestations rarely exceed 5% in a healthy orchard. Simply removing infested fruit at during thinning is enough to ensure that the majority of fruit are clean. Commercial orchardists back this up with a few discretely placed pheromone traps. These traps contain a sexual attractant for the male of the species, who consequently do not get around to fertilising the females.
Light Brown Apple Moth</1>
Unlike the grub of the codling moth, the looper grub, larva of L.B.A.M., lives outside the fruit. It still likes to hide though. Thinning fruit to singles helps reduce the number of hiding places for the grub and allows the birds to find them. They are susceptible to spraying with the bacterial spray, Dipel or Thuricide. Both these sprays contain a bacterium called Bacillus Thuringiensis which is specific to caterpillars. Unlike other sprays, organic or otherwise, it spares the predators. Remember that it is a living organism and will work better in cooler, moist conditions than hot, dry weather.
Woolly aphis, like all other sap sucking insects, will rush to the scene where there is an excess of nitrate in the soil feeding the plant. Prevention is better than cure, so curb the blood'n'bone if you are using this to feed your trees. The stronger animal manures, horse, chicken and pig, should be used sparingly also.
Liquid soap, also known as potassium soap wreaks havoc among this pest. Their waxy, water resistant bodies become wetted and they suffocate. Two commercial brands are 'Safers' and 'Clensil'.
Black spot, also known as apple scab is the scourge of apple growers. Though unsightly, light infestations do no harm. Heavy infestations can denude a tree, reducing vigour and increasing the likelihood of other pest and disease problems. Keeping the trees open and where there is a free flow of air will help reduce the incidence of this problem. Growing susceptible varieties such as Granny Smith and Red Delicious is no help. Try resistant varieties, such as Priam and Priscilla, if you know your neighbours have problems with spot.
The mainstay for control, used by both conventional and organic growers, is a spray of Bordeaux. This is a solution of copper sulphate and lime. There are many commercial preparations of copper that have a similar effect. It must be applied at 'greentip' to be effective; that is, just as the leaves burst from the bud. The fungus enters the leaves at this time, and spraying later will have little effect on the disease, other than to slow its progress.
The spores over-winter on the fallen leaves, so shredding the leaves with a mulching mower will reduce the number of spores. The earthworms more easily devour the smaller fragments of leaf. Raking the leaves under the trees and mulching over them will also help.
Biodynamic growers in New Zealand are claiming great result from the use of a 2% waterglass solution during the growing season. Waterglass is sodium silicate and it breaks down to silica (sand) and sodium carbonate (washing soda), so it is relatively safe. The concentrate (a 50% solution) is caustic and should be treated with caution.