A potted tree at Kew. Photo courtesy of Tampa Librarian/flickr.com
To plant a fruit tree in a container is easy enough. To keep the tree growing well and cropping well over a number of years is easier said than done. The reason is straightforward. By its very nature, a fruit tree is capable of looking after itself very well, providing the tree’s root system can fully explore the soil at considerable depth and width all around. The tree cannot do this if we restrict its rooting environment to a pot or a container of any size.
It is therefore very important to realize, once the tree is planted in a container, that the tree is no longer capable of looking after itself during the growing season. Obviously, the larger the container, the greater the volume of soil available to the tree. This in turn will mean that there is more soil available for the tree to explore.
Assuming the tree is provided with a regular water supply, by some means of irrigation, a larger tree can be maintained. Therefore 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 take in account 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 repotted 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. 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
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.
Soil and fertilizer
Make sure that whichever container is chosen, there are good-sized drainage holes in the bottom, loosely covered with pieces of terracotta pots to stop the holes from closing in future years. The best compost for trees in containers is John Innes compost No 3. 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.
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. A garden centre stocks 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.
Apples, pears, plums and cherries all can be grown in large containers. However the variety and rootstock used need to be chosen with care.
Good advice is a help once the particular situation and spot for the tree/trees are known. Pollination requirements need to be taken in consideration if regular fruiting is wished for.
Once the fruit has been picked it will keep best at the bottom of the fridge. 3 to 4 degrees Celsius is the optimum storage temperature for fruit.
Click here to read another article on soil and containers for trees grown in containers.
Photo courtesy of Garden Organic/flickr.com