Fruit tree nurseries usually sell fruit trees that are between one and three years old. This is for the simple reason that the younger the tree, the easier it is to transplant. Trees which are older than three years are obviously more impressive if you want an instant effect in your garden, but they require considerable care during transplanting, and they need a lot of after-care.
Transplanting of bare-root semi-mature fruit trees should only be attempted in the winter when the tree is dormant. As a general rule, do not expect the tree to grow or fruit in the year after planting, as it will take at least a year or more for it to recover and settle into its new location.
Why are older bare-root trees more difficult to transplant than younger ones? The main reason is that the bigger the tree when it is dug from the ground, the higher the proportion of the root system that is lost. It is the resulting imbalance between the roots and the aerial part of the tree after transplanting which is the main cause of problems. It means that the water demand of the aerial part, which is related to its leaf area, can easily exceed what the root system can supply. The tree then suffers drought stress that may stop it growing, or cause it to die.
To help prevent this happening:
- The aerial part should be pruned to try to restore a healthy root-shoot balance. Prune all the main branches back by about 20% of their length, or possibly much more in a difficult case.
- The soil of the planting spot should be improved if necessary, and the roots spread carefully in the hole.
- The tree should be kept well-watered (but not overwatered) and free of weed competition or grass - a thick mulch is very useful. Direct sunlight and windy conditions both increase water demand in the tree.
- Potting for a year might be helpful if the tree is easier to look after carefully this way.
In addition, particularly with trees which have been trained as standards, the newly-transplanted tree will be very unstable and should be held immobile at a height of about 1m by at least one substantial stake. This will give the roots a chance to grow into the surrounding ground and establish themselves firmly - which is likely to take more than a year.
If you follow this advice you should have a reasonable chance of success, but be aware that the bigger / older the tree the greater the risk that it may not survive.
As should be apparent from the above advice, the irony of attempting to transplant a semi-mature fruit tree is that to ensure success you have to prune it back so heavily that you lose the visual impact you may have been seeking. A much better alternative is to buy a container-grown semi-mature fruit tree, as several of the problems above are avoided - the container protects the roots from damage until planting. Even so there is still the risk involved in moving any semi-mature tree, and the other advice given above still holds. It is also worth noting that large container-grown fruit trees are very rarely available.