We produce our fruit trees on a selection of different rootstocks. The rootstock determines the overall size of the tree once it has reached maturity. You should choose the most appropriate rootstock for your given situation. Pruning techniques and timings can restrict the overall size of a fruit tree to a certain extent, but choosing the correct rootstock has more influence on keeping your tree at the desired size. Medium Sized Fruit Trees
The following rootstocks will produce a free-standing tree of around 4-5m in height and spread . They are commonly referred to as 'Semi-Vigorous', 'Bush' or 'Half Standard' trees. Once mature, most of the fruit can be picked from the ground. They should be planted 4-5m apart. These rootstocks are the best choice for growing trained fruit tree forms such as espaliers, cordons and fans.
MM106 or MM111 for Apple trees
Quince A or Pyrodwarf for Pear/Quince/Medlar trees
St Julien A for Plum/Damson/Gage/Peach/Nectarine
Gisela or Colt for Cherry
Torinel for Apricot
Large Sized Fruit Trees
The following rootstocks will produce a free-standing tree of around 8-10m in height and spread. They are commonly referred to as 'Vigorous' or 'Standard' trees. Once mature, the fruit will need to be picked either from a ladder or from the floor. They should be planted 8-10m apart. Choose from the following rootstocks if you plan to graze sheep or cattle under your fruit trees. They will eventually make the large trees you would expect to see in traditional westcountry orchards, and are the required rootstocks for Natural England's Stewardship Schemes.
M25 for Apple trees
Pyrus Kirchensaller for Pear/Quince trees
Brompton for Plum/Damson/Gage/Peach/Nectarine
F12/1 for Cherry
Other Considerations When Selecting Rootstock
Aside from rootstock selection, vigour also varies between fruit tree varieties, so a more vigorous variety will produce a larger tree than a weaker variety on the same rootstock. Also remember that your soil type and location will have an influence on overall tree size. If for example you grew the same variety on the same rootstock in two locations: Location A : a deep, fertile soil on a sheltered site and Location B: a shallow, poor soil on an exposed site, the trees growing in Location A will be bigger overall.
For less-than-ideal sites, be it windy, damp, or with low-fertility/shallow topsoil, you are best choosing a more vigorous rootstock, which has a better chance of doing well than the same variety on a less vigorous rootstock.