Nearly all apple trees sold in New Zealand are grafted or budded onto rootstocks. Rootstocks are represented on the plant label or in the plant description by a series of letters and numbers.You could be forgiven for thinking that this is a secret horticultural code and I guess to the uninitiated it is just that.So what do the numbers actually mean and where do they come from?

Nearly all of the apple rootstocks used today were researched and selected by the Pomologists^ (don't you love that word) at East Malling Research Station in England.Their work goes back to the 1900's where they studied heritage apples that had been in use for many centuries in Europe.Each important apple or clone was given a number preceded by an M to represent Malling.Work was also done with the John Innes institute at Merton and the Long Ashton Research station so these rootstocks were represented either by MM for Malling-Merton or EMLA for East Malling-Long Ashton.See its not that complicated at all.The research centre continues to play a significant role in horticultural development today.

Rootstocks determine the eventual size of the tree and how the tree responds to growing conditions.Except for very dwarf fruit trees the rootstock does not affect the actual size of the fruit. The rootstock begins at the bottom of the tree with; you guessed it, the roots and then grows to form the lower part of the tree, forming about 20cm of the main trunk.The scion i.e. variety of apple is then grafted or budded on to the rootstock and forms the rest of the tree determining what type of apple (Royal Gala, Granny Smith, Golden Delicious etc) that you will be munching on.There is usually quite a distinctive line where the 2 are joined together in growing harmony.It is very important when planting your apple tree that this join is visible above ground.Any growth that appears below the join should be rubbed or cut off as soon as it appears.Rootstocks do not impact on pollination - apples are generally self fertile however they will generally crop better with a closely planted companion.