Chapter 7
Caring for your trees
Once you have planted your trees, there is a sense of sitting back and waiting for fruit production to begin, but this is not a time for doing nothing. The first years of a tree’s life are the most important: formative pruning, feeding and watering will all ensure that the young tree gets off to a good start. There is a host of pests and diseases that can potentially threaten your tree, and regular inspection of your trees will allow you to nip these problems in the bud.
The principles of pruning are examined in Chapter 8, while pests, diseases and other problems, and the means of combating them, are dealt with in Chapter 9.
This chapter covers the other aspects of caring for fruit trees, which are often overlooked, such as ensuring a good water supply for the roots, paying attention to feeding requirements and preventing heavy crops from causing problems further down the line.
Heavy crops can bend branches down to the ground, as seen here on a Bramley’s Seedling apple tree.
Watering fruit trees
It is only during the first year or two after planting that most trees will need to be watered. This time can be stressful for trees: their roots have been chopped when they are lifted from the ground in the nursery and they suffer from the shock of being transplanted. The roots can struggle to take up all the moisture that the tree needs.
Symptoms of drought stress are: leaves failing to open well all the way along branches in the late spring, followed by foliage yellowing and dropping off during the summer. Fruit can be small and drop off early.
Watering may also be necessary on free-draining soils, in areas where rainfall is particularly low and where a tree is planted close to a wall. In these situations, it is useful to insert a vertical section of pipe when planting to ensure that water can get down to the roots. It is important to add water in sufficient quantity, so that it reaches down into the soil rather than wetting the surface. If this is the case, roots will be attracted to the surface to find moisture.
Where a number of trees need watering, it can be useful to fit a trickle irrigation system – a hose with small holes in it so that water gradually permeates the soil, rather than running off when it is applied suddenly. Benefits will also be seen from mulching with organic matter in the spring when the soil is damp; this helps to conserve soil moisture over the growing season.
Feeding fruit trees
Most fruit trees do not require high levels of feeding. If the soil has been prepared well before planting time, and attention paid to any deficiencies found, this will go a long way to providing the trees with the nutrients that they require. However, if trees are to perform well, some supplementary feeding is likely to be necessary. Before feeding your trees, ensure that they are not being starved of nutrients by grass or weeds growing close to the trunk. A circle of approximately 50cm (1'8") radius around the tree should be kept clear of vegetation.
Keeping an area around the tree free from grass allows it to establish without competition for water and nutrients.
Like all plants, trees are able to convert sunlight, water and carbon dioxide into the sugars that are needed to enable plant growth. However, additional nutrients are needed to keep the tree healthy and fruiting well. These nutrients are discussed in Chapter 1 (page 20).
Nitrogen (for growth) and potassium, or potash (for fruit formation and development), are the two most important nutrients for fruit trees. A deficiency of either of these will lead to a tree becoming starved and unproductive, but it is also important not to feed a tree too heavily. Excess nitrogen leads to soft, sappy growth that is prone to disease, while excess potassium can lead to problems with bitter pit and with trace-element absorption.
Phosphorus, magnesium and trace elements such as sulphur and copper are also needed. So, unless you are trying to correct an imbalance of a particular nutrient, you will be looking to apply a balanced fertiliser with a high level of potash.
Non-organic and commercial growers have the luxury of choosing fertilisers with specific N (nitrogen), P (phosphorus) and K (potassium) levels. Organic growers, looking to use more natural sources of plant food, often find it harder to obtain the exact constituents of particular plant foods. Organically based fertilisers designed for fruit trees are now appearing on the market, but they are still few and far between.
Seaweed contains low levels of the NPK nutrients normally found in synthetic fertilisers, but does contain high levels of all the trace elements and minerals that are important for plant growth. It also contains plant hormones, including cytokinins, which are thought to regulate plant growth. Seaweed is an excellent plant food for fruit trees, although regular use can be expensive; it is available as a liquid that can be used as a foliar feed, or as seaweed meal for adding to the soil. A study in 2008* found that seaweed, sprayed five times during the growing season, “stimulated the growth of shoots and leaves, [and] caused an improvement in flower quality ...” There was also evidence to show that seaweed “improved the fruit set and size of apples”.
Animal manure and compost are both excellent mulches to place around fruit trees. They contain the major nutrients in small quantities, as well as good levels of trace elements. They also add humus to the soil. Take care to keep manure and compost away from direct contact with the trunk.
Pelleted chicken manure is a useful, organically acceptable fertiliser with a well-balanced supply of nutrients. Wood ash, either from a fire in the house or from a bonfire, is a good source of potassium. It is, however, highly water soluble, so ash from a bonfire must be used before rain washes away the useful nutrients. Liquid feeds made from comfrey or nettles can be used on fruit trees. Nettles are higher in nitrogen; comfrey in potassium.
Management techniques
Aside from pruning (see Chapter 8), there are several methods of manipulating fruit trees to help achieve the required balance between growth and fruiting.
Correcting biennial cropping
Biennial cropping is the tendency of certain trees, usually apples and pears, to crop heavily in one year and lightly in the next. Although certain varieties have a tendency towards biennial cropping, it can also be induced by frost damage or an over-heavy crop. Once biennial cropping sets in, it can become an established pattern unless something is done to correct it. The simplest way is by not allowing the tree to carry a heavy crop in the year that it would normally do so. This can be achieved by thinning the blossom or young fruit in the heavy-cropping year, or by pruning out some of the fruit buds in the winter before the heavy crop is expected. I prefer thinning the young fruit, because by the time that the young fruits have formed it is possible to see how heavy a crop the tree is likely to bear, and consequently how hard the thinning needs to be.
It can be helpful to see a fruit tree as having only a limited amount of energy. This energy can be used for various functions in the tree, such as putting on growth and fruiting, or for fruit bud development. Fruit buds begin to form in the summer before they will become fruit. If, at this point, the tree is carrying a heavy crop, there will be less energy available for the initiation of fruit buds. So limiting the heavy crop means that the tree is more likely to have energy to form fruit buds, which will carry fruit in what would otherwise be the quiet year.
Fruit thinning
Fruit thinning is also used to ensure that a tree carries an optimum amount of fruit, and fruit of good quality, in the current year. A heavy crop can be a strain for the tree, as well as increasing the likelihood of small, malformed fruits that are more prone to disease. Thinning the fruit means removing some of a cluster of a fruit, leaving individual fruits with plenty of room to develop.
Some varieties, such as Victoria plum, are prone to constant heavy cropping. Although this might seem desirable, it can lead to broken branches, which are then open to disease such as silver leaf. Thinning the young fruits, once a heavy crop is apparent, helps to avoid this. Thinning can be supplemented by supporting heavy branches with a prop or stake, usually made from wood with a forked branch at the top. Branches can also be supported from a central stake – a process known as maypoling, as shown in Diagram 14 overleaf.
Part of a pear tree before and after the fruit has been thinned in the spring.
Diagram 14 Maypoling, used to support branches that are heavy with fruit.
Other varieties, such as the apple Falstaff, tend to carry a heavy crop while tree is still young; although this might seem to be desirable, it can lead to the tree becoming stunted at an early stage, because there is little energy left over for growing as opposed to fruiting.
Altering branch angles
The more upright a branch is, the more vigorous it will be and the more likely it is to be largely vegetative in nature. Conversely, a horizontal branch is less vigorous and more likely to bear fruit.
We can use this knowledge to alter a tree’s habits. For example, some varieties tend to grow in an upright shape, especially when they are young. Tying down the branches will bring them into fruiting more quickly as well as reducing the vigour of the tree. Ties, usually of twine, can be attached to heavy stones or metal hoops inserted into the ground. Once a branch remains in position when the tie is taken off, the tie can be removed altogether.
The danger with this technique is of overdoing it. The branches of fruit trees tend to become more horizontal with age, so if they have been tied down when young they can end up dragging on the ground, particularly with the weight of heavy crops. So, this technique is best applied to trees that are unfruitful and upright in their growth, rather than indiscriminately because you are impatient for a tree to bear fruit.
The same technique can be applied to wall-trained trees while they are establishing. Vigorous, more upright shoots can be brought down towards the horizontal to reduce their vigour, while weak horizontal growth can be tied up to increase its vigour. This can be useful to correct uneven growth on a fan-trained tree.
Caring for fruit trees in pots
Planting fruit trees in pots is covered in Chapter 6, but once you have planted the tree, there is still maintenance to carry out, which can be rather different from looking after trees planted in the ground.
Siting
The beauty of growing fruit trees in pots is that you can move them around to take advantage of different situations. For most of the year a warm, sunny position is ideal, preferably sheltered from strong winds. It is a good idea to tie the tree loosely to a wall or post so that it cannot blow over.
For the winter, some of the more tender trees, such as peaches or apricots, will appreciate the shelter of an unheated greenhouse. Don’t place them in a heated greenhouse, because, like most fruit, they have a need for a certain amount of chilling in the winter. A greenhouse will also give protection against spring frosts, which can damage blossom, although the trees will need to be accessed by pollinating insects. Alternatively, you can pollinate the blossom by hand (see Chapter 3, page 39).
In cold areas, it is worth wrapping the pot in bubble wrap – partly, in the case of clay pots, to prevent cracking, but also to protect the tree’s roots from hard frosts.
Watering and feeding
Paying careful attention to watering and feeding is vital for pot-grown trees. The soil should be kept moist, which means watering daily at the height of summer, reducing to very little watering during the winter. It is important to avoid the extremes of waterlogging and drought, both of which can result in the tree shedding fruit.
The nutrients in the compost at planting time will soon be used up, necessitating additional feeding. Every spring, a top dressing can be applied to enrich and refresh the compost. Manure and compost make good top dressings, but the best material is homemade worm compost, a very concentrated source of nutrients.
Liquid feeds will also be needed, particularly those high in potassium, such as tomato food or comfrey liquid. Seaweed is also helpful in alleviating the potentially stressful conditions of growing in a pot. You can tailor the feeding to the requirements of different trees: stone fruit, for example, will need more nitrogen, particularly at the beginning of the growing season. Fruit trees will benefit from feeding every 7-10 days while the fruit is swelling. The feeding can be stopped once the fruit has been harvested.
Re-potting
The tree will need re-potting every year until it reaches maturity. Late autumn to early winter is the best time for this. Carefully remove the tree from the old pot, partly by tipping the pot and partly by pulling on the trunk. Once the tree has been removed, tease out the roots and trim back the protruding ones. Thick roots without much fibrous growth can be cut back harder. Removing some of the old compost allows room for new, nutrient-rich compost when the tree is re-potted.