Nearly all fruit trees are grown on a rootstock. When you come to buy and plant a fruit tree yourself it is important to understand exactly what a rootstock is as well as how it will influence the growth and vigour of the tree itself.
Knowing this information will ensure you have the right tree for the space you are intending to put it and that it will grow in a controlled way.
What Is A Rootstock
A rootstock is basically a root system that a fruit tree is grafted onto. What this root does primarily is control the vigour and eventual size of the tree.
In practice, this means you can choose a tree that is perfectly suited to the space you have.
If you have a large area or an orchard then an M25 rootstock will allow an apple tree to grow up to 10 metres / 32 foot tall, whereas the same apple trees grafted to an M27 rootstock will only reach a height of 1.5 metres or 5 foot.
By selecting the right rootstock a fruit tree won’t be able to outgrow your garden and will still be healthy and produce plenty of fruit.
Why Are Rootstocks Used?
Let’s use the example of an apple tree rootstocks.
Apple trees are always supplied on a rootstock, the reason being the way they are pollinated.
If you take the pip from an apple and plant it, it will end up growing into a different variety of apple because they are cross-pollinated.
Apple blossom can only be pollinated by the blossom from another variety of apple tree to produce fruit. The resulting pip will grow an apple tree that contains characteristics from both the apple varieties that produced it.
Rootstocks Are Made By Grafting
We know if we want to grow a new fruit tree of a particular variety we can’t just plant a seed or stone from the fruit itself. What happens is a cutting from the variety of fruit we want to grow is taken and grafted to a rootstock
Grafting Fruit Trees
The process of grafting means we can effectively clone a fruit tree by taking graftwood or a scion from a healthy tree and attach it to a rootstock.
The rootstock chosen will dictate the eventual size of the fruit tree.
When you come to buy a fruit tree you will see the evidence of the grafting which will look like a bulge in the trunk just above the roots. This bulge is where the scion wood has been joined to the rootstock and healed. When you plant a fruit tree this bulge should be above ground level.
Types Of Rootstock
Most rootstocks are coded so it is not immediately obvious as to how big the fruit tree is going to grow. Codes like M9 OR MM106 are used which at first is quite confusing so let’s categorise the types of rootstocks you will be able to buy.
Dwarfing & Semi-Dwarf Rootstocks
If you look at an ancient orchard you will probably notice the trees are quite large in size and fairly substantial. It wouldn’t be practical for many people to have such large trees in their gardens as they take up too much space.
Fortunately, rootstocks of dwarf and semi-dwarf varieties limit the eventual height of a tree meaning a smaller tree well suited to small gardens or even containers. The beauty of these smaller rootstocks is that all the maintenance, pruning and picking of the fruit can be done from the ground without any ladder or steps.
Benefits Of Dwarf Rootstocks
The clear advantage of using dwarfing rootstocks is the tree isn’t going to take up too much space. You will often be able to have multiple types and varieties of fruit tree in a fairly modest garden.
Another big plus point with dwarf rootstocks is that they tend to bear fruit sooner than larger trees. The benefit of being smaller is they reach their established size sooner and can then put more resources into fruiting
Disadvantages of Dwarfing Rootstocks
There are obvious benefits to dwarf varieties of rootstock but that is not to say there are no downsides.
In general, smaller rootstocks need more care and nurturing. They require clear ground around the base of the tree where larger rootstocks are not so finicky. You will also have to pay more attention to feeding and fertilising the tree as the roots are not as expansive.
The one other thing that is clear is that the smaller the rootstock, the smaller the tree and therefore this limits the amount of fruit that it can produce. This is not likely a problem for most people as vigorous rootstocks tend to produce too much fruit for a single household.
Vigorous rootstocks will produce trees that can grow up to 10 (33’) or more.
If you happen to have a large amount of space or a field then a tree of this size will produce an abundance of fruit, possibly more than you can eat.
The clear benefit of a vigorous tree like this is they are mightily impressive. Many ancient orchards are these large trees and if you have visited one you’ll know they really are something to behold.
The disadvantage of a large fruit tree, of course, is they need to be managed and harvesting is a lot harder. In fact, most of the apples or fruit is going to be out of reach so most of the fruit will be windfalls which will not keep for more than 3 or 4 weeks.
Semi-Dwarfing Rootstocks – The Best Of Both Worlds
A good trade-off between vigorous and dwarfing rootstocks is semi-dwarfing. Apple rootstocks, such as MM106, pear rootstocks such as Quince A & C balance size and yield well and will do well in average or large gardens.
The clear benefits are that you can manage to harvest from the ground or with long-handled tools and the tree itself will establish fairly quickly.
Rootstocks For Different Fruit Trees
Depending on what sort of fruit you want to grow will determine the rootstocks you need to consider. Each variety of fruit tree may have different codes or names for their rootstocks so the most common or popular have been listed below.
Rootstocks for apples, in the UK, have codes usually starting with M or MM. These denote the research stations where the particular rootstocks were initially developed, either Malling or Merton Malling.
A very small dwarfing rootstock that has a mature height of 1.2 – 1.7 (4 – 5 feet) and a spread of 1.5 meters (5 foot). Will need clear ground around so there is no competition from weeds and good staking.
A small dwarfing rootstock with a mature height of 1.7 – 2.5 (5’6” – 8 feet) and a spread of 2.5 meters (8 foot). Needs staking and no competition. Can be grown as a bush, cordon or stepovers or in a container.
A semi-dwarfing rootstock that has a mature height of 2.5 – 3 meter ( 8 – 10 feet) and spread of 3.5 meters (11’ 6”). Suitable for training as fans or espaliers and can be grown in a large container.
A semi-dwarfing rootstock with a mature height of 4 – 5 meters (13 – 16 feet) and a spread of 4 meters (13 foot). Needs to be staked and is suitable for training in most forms.
A semi vigorous rootstock with a mature height of 5 – 8 meters (16 – 26 feet) and spread of 7 metres (23 foot). Suitable for orchards or larger gardens.
A vigorous rootstock that has a mature height of 6 – 10 metres ( 20 – 33 feet) and spread of 7 – 10 metres (23 – 33 feet). Suitable for orchards or very large gardens.
Pears are often grafted onto Quince rootstock so the naming that applies to pear rootstock is confusingly called Quince A or C. They are also grafted to wild pear rootstocks.
A semi vigorous rootstock and the smallest available in most nurseries. The mature height will be 3 metres (10 foot) with a spread of 3 metres. Will take around 4 or 5 years to produce fruit and can be trained into most forms.
Similar in size to Quince C this new rootstock is less prone to pests and problems with soil and will start producing fruit quicker than Quince C
A medium vigorous rootstock that produces trees that mature at around 4 metres (13 foot). Will take 4 – 6 years to start producing fruit and can be trained into most forms.
The smallest rootstock available for plum trees. The mature height will be around 3 metres (10 foot) and the spread 3 metres. It is suitable for training in all forms and will bear fruit after 2 – 3 years.
This is the most popular or common rootstock for plums. It is semi vigorous and the mature tree will grow to 3 – 4 metres (11 – 15 feet). Will take around 3 – 4 years to bear fruit
This is a full size, vigorous rootstock which is used for standard trees. Will tolerate most soil and growing conditions and has a mature height of 5 – 6 metres (16 – 20 feet). Only suitable for very large gardens or orchards
In the past cherries were grown on huge trees that could grow up to 15 metres tall. This of course caused all sorts of problems protecting the cherries from birds and harvesting. The introduction of rootstocks produced much more manageable trees.
This is probably the most popular rootstock for cherries and a relative newcomer. Mature sizes are 2.5 – 3 metres (8 – 10 feet) with a spread of 3 metres (10 feet). This size of a cherry tree means you can net the fruit to stop birds from stripping the tree and can be trained relatively easy.
A semi-dwarfing rootstock that has been overtaken in popularity by Gisela 5. The mature tree will grow to 3.5 – 4 metres (11 – 15 feet) and will grow well in most soil conditions.