Growing apple trees in pots or patio containers has a number of benefits:
- You can move the trees into a frost-free garage during bad winter conditions or to avoid spring frosts. (Do not bring them into a heated house though).
- They provide a decorative and fruitful effect on patios, enhanced by an attractive container.
- You can grow trees in very small spaces, ideal for houses with no gardens.
- If you think you might be moving house, you can take the trees with you.
The main disadvantage is that a container or pot is quite a difficult environment for a fruit tree, particularly if you accidentally forget about it for a few days in hot weather. The trees will need regular watering throughout the summer - this could be 2-3 times a week. In warmer zones you will probably need an irrigation system.
Rootstock choices when growing fruit trees in pots
There are several approaches to choosing fruit tree varieties for growing in containers and patio pots. The most common approach is to use dwarfing rootstocks, which will keep the size of the tree down to less than 2m / 6ft or so.
A more recent approach is to use more vigorous rootstocks than are traditionally used for patio fruit trees, relying on the container itself to restrict the root size. This approach has an advantage that the tree may survive a bit longer if you forget to water it (but it will still need much more attention than a tree in open ground). This approach is perhaps more suitable if you want a more substantial tree than the usual patio-container tree, e.g. to grow in a large planter.
Another approach is to choose fruit tree varieties which are slow-growing and/or not vigorous. In these cases you could use a more vigorous rootstock than the very-dwarfing rootstocks usually selected for patio-grown fruit trees.
In all cases the tree will need to be regularly watered and fed.
Pot sizes
Pots and containers come in all kinds of sizes, and can be described by either volume (capacity) or diameter, and may be round or rectangular. This makes it difficult to prescribe exact measurements, but the diameter across the top is often a good starting point.
- Apple trees on dwarf rootstocks can go in a pot of between 18" - 22" / 45cm-60cm diameter. Alternatively look for containers with a volume of 40-60 litres.
- For other new fruit trees the most suitable size pots or patio containers will be those which have a top diameter of at least 60cm / 2ft. In the case of a square container this equates to sides of about 16" / 40cm and a volume of 60 litres.
You can then re-pot every year or so, increasing the size by 10-20 litres per year until the tree stops growing (which will be after a year or so for small trees and after 4-5 years for larger ones). However you do not have to re-pot each year, you can use a large container straight away.
If in doubt, too big is far better than too small.
If you are using a dwarf rootstock, you will need to anchor a thick bamboo cane into the bottom of the container to support the tree.
You will also need to make sure that the container is stable since, particularly when the tree is in leaf, it can act like a sail and get blown over in a strong wind, potentially damaging both the tree and the container. Containers with a narrow base are therefore best avoided. If you put a stake in the pot then you may be able to anchor it from the top to a nearby fence.
Soil requirements for pot-grown fruit trees
It is best to use normal soil, or a mix of compost and ordinary soil - do not use all compost as it dries out too easily. Put some large pebbles or broken clay pot pieces in the bottom to allow drainage. A decorative mulch on top of the soil will help keep moisture in. The key thing when growing fruit trees in containers is not to let the soil dry out.
After the tree has reached its final size it is also worth replenishing a proportion of the soil every 3-5 years. Some authorities suggest root-pruning at this time as well, in other words pruning the roots back by about a quarter, which will encourage the tree to continue growing whilst preventing it getting too big.
During the growing season, a bit of plant food helps as nutrients are easily lost from containers over the year, but be very cautious of over-enriching the compost, particularly in the first year as this can cause the trees to stop growing after they come out of dormancy.
We do not recommend using "organic" or soil-less composts, these can be successful but require expert knowledge to ensure the tree stays healthy.
Problems with pot-grown fruit trees
The main disadvantage of growing a fruit tree in a container is that it is actually a very difficult environment for the tree, so the tree will need a quite a bit more attention than if grown in open ground. The failure rate for trees planted in containers is far higher than for trees planted in open ground - invariably because the tree was not watered.
Watering
Watering is by far the biggest issue when choosing to grow fruit trees in containers. You will not usually need to water the tree over the winter when it is dormant, but during the rest of the year be prepared to water at least twice a week, and probably daily during sunny warm weather. If you go away for a period make sure you get someone to come in and water the tree.
If the tree looks unhappy or unhealthy, the cause is often stress brought on by insufficient watering. As the tree weakens it is less able to fight of insect and fungal infections.
A common misconception is that if there has been rain during the week, or it has not been hot and sunny, the tree will not need watering. This may be true for trees grown in open ground, as their roots can extract moisture from rain falling in a wide area around the tree. However the soil surface area of a typical patio container is usually very small, and it would take a deluge of rain to bring enough water into the container.
The smaller the container, the more important it will be to water regularly.
Winter protection
If you live in an area where winter temperatures fall well below freezing you will need to take steps to protect the tree. This is because in open ground the roots of the tree are insulated by the soil around it, whereas with a pot-grown tree freezing air can get close to the sides and even underneath the roots of the tree. A thick protective fleece around the container may be sufficient in some areas but usually you will need to move the tree into shelter, such as a cold garage for the winter. Never put the tree in a heated house.