I have been told that the height of the graft on the rootstock affects the size of the mature tree, i.e., the higher the graft the smaller the resulting tree will be. For space reasons I need to keep my trees in containers, and therefore most of the apples are on M9, or P22, but I would like the improved resistance to disease that I would have with M26. If the information regarding the effect of graft height on size is true, how high up a M26 rootstock should I graft to achieve a mature tree intermediate in size between M26 and M9? Also, all the trees are currently in the largest size of duraco pot. Do I need to anticipate the M26 ones outgrowing their pots?
i could be wrong but thats the first i have ever heard of the size of the tree depends on how far up you graft them. to my knowledge the size is dependant on the type of rootstock if its not a dwarfing rootstock it does not mater where on the rootstock you graft it it will will not be dwarf. i donot know wich apple rootstocks are dwarfing and wich ones are not. i am no expert just a hobby gardener but have never ran across any information regarding graft heigth affecting the size.
My thanks to Mikey and Ron for their replies. I suspected that it was folklore, and dubious, but I could hardly appear to doubt the word of the person who told me, so I couldn't ask any of my usual circle.
If you want improved disease resistance you need the GENEVA series in apple rootstock. All are Dwarf varieities available in Geneva 11, 16 and so forth. Contact cummins nursery the founder of the Geneva series. M9 M26 are very suseptible to rootstock blight.
