Apple Tree Rootstocks

If you grow an apple from a seed, 3 things will occur:

(1) The tree will get very big - around 30 feet.

(2) The flavour of the apples will be unpredictable. They will not be the same as the apple from which the seed came, as they will be the children of it and another unknown variety.

(3) The root system could be susceptible to disease. 

In order to avoid all 3 things, most apple trees you buy will consist of 2 parts:

(a) A branch cut from an existing tree, grafted onto 

(b) the root system from a different tree, which is known to stop growing at a certain size and generally be disease resistant.

So you basically grow one small tree which you want the roots from, then at some point cut the stem off it, and graft the branch of a tree you like the apples from onto it. Hey presto, the tree will grow to produce the apples you want but get only to the size you want. So when choosing an apple tree, the trick is to decide which size of tree you want based on the rootstock. I have set out a table of these below, from smallest to biggest.

Rootstock name - Eventual height of tree - uses/requirements 

Very dwarfing

M27 - 2 metres - Needs staking

Dwarfing

M9 - 2.5 metres - Needs staking

Semi-dwarfing

M26 - 3.5 metres - Needs staking

Semi-vigorous

MM106 - 4 metres - No need for stake once established

Vigorous

M25 - 6.5 metres - No need for stake once established