Containers are a great choice for growing your dwarf fruit trees. Planting these specialised, smaller trees in containers gives you greater flexibility when it comes to positioning the trees. You can turn the pots to prune or harvest the trees, and you can move trees onto a patio or into a greenhouse to protect them from cold winter weather. The main issues you will run into with containers is drainage and space. You want to have a growing medium that drains well, and containers big enough to allow your trees to reach their potential.
Select a container. As a general rule of thumb the container you transplant your dwarf fruit tree into should be at least 6 inches wider in diameter than the container it came out of. That being said, the larger container you choose, the less frequently you will have to uproot and repot your trees. Wine or whiskey barrels cut in half are a great, economical container for growing dwarf fruit trees in.
Make sure your container has adequate drainage holes. In a whiskey or wine barrel go ahead and drill out a centre hole about 1 inch in diameter, as well as 4 surrounding drainage holes of the same diameter spaced between the centre hole and the edges of the container. If you want, you can cut and fit a piece of metal mesh over the drainage holes to prevent the soil from leaking out, but it is not necessary.
Put a 1 to 2 inch layer of gravel in the bottom of the container. This will help to facilitate drainage. Drainage is essential to your tree's performance. The roots of fruit trees do not like sitting in water. They need adequate drainage or they will rot and the tree will die.
Now put some potting soil or other growing medium into the container. Potting soil works fine, but a lot of folks prefer a solution of one part sand to one part peat moss to one part perlite. Whatever growing medium you choose, you want the soil to be loose enough that it drains well, but not so loose that the water runs through before the tree has had a chance to absorb it into the roots. Fill the container to a point where when you rest the root ball of the fruit tree atop the soil, the top of the root ball lies about 4 inches or so beneath the rim of your container. Then fill in around the root ball with more potting soil or other growing medium.
Water your fruit tree frequently. A fruit tree growing in a container requires a lot more watering than one grown in the ground. This is because the soil dries out much quicker. During the spring you will want to water the tree several times a week, and during the hot summer months give it a good drink on a daily basis.
Fertilise your fruit trees in containers about every four to six weeks. Growers recommend a balanced fertiliser for fruit trees in containers; a fertiliser containing relatively equal parts of nitrogen, phosphorous and potassium. Talk to your local nursery person about the best fertiliser for the specific type of fruit trees you are growing.
Move your trees into the sun. Fruit trees perform best in full sun, though they can handle partial shade. If you are moving a tree from a shady area to a sunny area, ease the tree into the new light zone. A dramatic change in light conditions can shock the plants and cause damage.
Move your trees to a protected area during the cold winter months. Many dwarf fruit trees, particularly certain types of citrus, cannot tolerate a freeze. These trees must be protected by being moved onto a patio, under an overhang, or into a greenhouse.
Certain types of fruit trees will perform better in containers than others. Most fruit trees can spend some years in a container, but will then need to be transplanted into the ground to reach their full potential. Talk to your local nursery person about the types of trees that will perform well in your area and in containers.