Are fruit trees suitable for growing in a pot, and producing fruit? Just visualize the enormous change we humans present to potted fruit trees. Under normal conditions, planted in the ground, the trees can explore and find the nutritional elements they need in a great volume of soil. If they cannot find what they need close by, the tree roots grow either deeper or further outwards until they finds the major/trace elements essential for their wellbeing. If however we plant our trees in a container, then we dramatically curtail root growth and make the trees very much dependent on us for their nutrition and moisture requirements.
Some plants are more fruitful in containers. Take for example the fig. If it is planted in good, well-drained soil without any root restriction, it will tend to produce wonderful leaves. But this is often, under our climatic conditions, at the expense of fruiting. A fig planted in a pot grows less and fruits much more.
How to grow fruit trees in containers
The first principle to take in account is what final tree size is desired for the long term. Container size is therefore a very important decision. Also one needs to consider the fact that by means of tree training and summer pruning, a smaller tree canopy can be maintained. Espaliers, cordons, and fan-shaped trees are all realistic possibilities. A fruit tree in a smaller pot will by nature remain a smaller plant and therefore needs less pruning and is easier to maintain. However a small tree will have a reduced cropping capability. It is as well to remember that in general terms about 30 healthy green leaves are needed for each apple, bringing the fruit to maturity and optimum size.
Size of the container
Regarding the size of the pot or container, you can start with a pot with a rim size of 15 to 20 cm. However after year two, the tree needs to be re-potted to a larger pot with a 25 to 30 cm rim. The ideal container needs to be at least 45 cm in width, with a minimum depth of 40 cm. After a couple of years, repot the tree in a larger pot. A soil-based compost should be used for planting the tree in a pot. Also it is just as well to remember that if the tree is placed on a patio or near a wall, it is liable to blow over and therefore needs to be secured. This of course is of less importance when the tree is placed inside a building. In that case it is just as well to remember the tree will need plenty of light in order to do well.
Type of container for potted fruit trees
There are numerous choices available in the form of containers for fruit trees. Containers have a great effect on the wellbeing of fruit trees. To begin with, the size/volume of the tree is in direct relation to the size and capacity of the container. The bigger the container, the larger the tree, of course as long as soil and water are readily available for the tree roots to explore. Secondly, not only the dimension of the container used is of influence. It does make a difference whether it is a clay pot, plastic or made from another material. Roots of fruit trees like to stay cool. Thin plastic pots are not suitable. Double-walled plastic is fine. Plastic pots should not be placed in full sun as the roots like to be growing in moist compost of moderate temperatures, and plastic in the sun gets hot and transfers the heat to the soil. Plastic pots in the shade are fine. Half an oak barrel or the equivalent is fine too. Smaller wooden containers have a tendency to dry out too quickly. Metal containers in the long term are less suitable. Large clay pots are very well suited for fruit trees.
Whichever pot is chosen, the drainage holes must never be blocked. Excess water in the container kills a tree just as quickly as drought. Therefore make sure the holes are loosely covered with broken clay pot pieces to stop the holes from closing in future years.
Soil and fertilizer for potted fruit trees
The type and quality of soil is of the greatest importance. What is a good quality soil? A good soil has a crumb-like structure, and the sand and clay particles are present in such a ratio to make it possible for the tree to take up everything that it needs; oxygen, water and the essential nutritional elements. Soil-based John Innes compost number 3 comes the closest to fulfilling these requirements.
It is an advantage to mix some grit into the compost in order to keep the soil-based compost open enough for water to travel right through the container and not just along the sides. Mix some slow-release fertilizer into the compost. Follow the instructions on the packet. Too much fertilizer will harm the tree and weaken the root system. When filling the container, leave some room at the top without compost to make watering easier. Do make sure that the compost is thoroughly wetted after planting, and maintain the moisture content of the compost throughout the growing season.
As mentioned above, the tree will need to be fed annually. The best time to do this is in the spring. During the summer months, foliar feeding is of great benefit to the tree, provided you follow the instructions on the packet closely.
When to feed and how to water your trees in containers
A watering can is not ideal. Particularly in containers one needs to pay attention to the fact that more often than not the water, when applied using a watering can, escapes via the sides of the pot or container. The water comes through the drainage holes and one thinks one has done a good job of watering. The centre of the pot stays dry and the trees suffer from water stress. It is better to apply the water via a drip system, which applies little water each time it drips. Also, soil is often very difficult to rewet if allowed to dry out too much.
Apply water and nutrients at regular intervals, definitely before wilting occurs. For fruit trees, apply a general purpose fertilizer such as Growmore in the early spring. To strengthen fruit buds, apply a light dressing after picking the fruit. Slow release fertilizers can do a good job. You can also foliar feed your trees with very good results.
Some cooking apples will do reasonably well if partly shaded. Plums do also well in slightly shaded positions. However cherries, pears and peaches do best when grown in full sunlight. No fruit tree does well if put completely in the shade of a wall or another tree.
Which types of fruit tree can be grown in containers?
Single stem trees such as cordons usually do well. More demanding are espalier and fan types of trees. Pears and apricots are ideal for growing as espaliers. Cherries, peaches and plums do better when grown in an open fan shape.
Over-cropping of potted trees
It is very nice to grow a good crop. If you overcrop the tree, the following year the tree does not crop at all or only a little. It therefore pays to thin the fruitlets, whichever type of crop it is.
Pests on potted trees
Regarding pests, it is important to control greenfly/aphids and caterpillar. Fungal diseases such as mildew, scab, canker and brown rot can sometimes be a problem. Garden centres stock various products which will help to control these diseases.
All types of birds love to peck or eat fruit. Have a net handy before the fruit is at the vulnerable stage.
Fruit varieties for growing in containers
Apples, pears, plums and cherries all can be grown in large containers. However the variety and rootstock used need to be chosen with care.
Cherries in containers
From the point of view of controlling bird damage, you are far better off growing a cherry tree in a container. The tree will stay relatively small and is therefore easier to cover with a net, to stop the birds eating your cherries. Mind you, the size of the container is crucial. It needs to be at least 50 cm across and 45 cm deep. This container needs to be filled with the best top soil available. In the bottom of the container you need to have a couple of 2.5 cm sized drainage holes, which need to be covered with broken terra cotta pot fragments to stop the holes from silting up.
As cherries themselves are 90 percent water, you must make sure the trees never dry out! Water the trees at least twice a week with 5 litres of water each during the growing season. When very hot and dry, 10 litres of water each. Feed the trees with “Growmore” and follow instructions on the packet. Pruning is best carried out when harvesting is completed. This to avoid the pruning wounds becoming infected by the spores of different fungi such as “Silver leaf,” and not to forget the disease called Bacterial Canker.