Ligrower,

You are correct in the vigor of the apple variety having an
impact on height also. I cannot vouch for granny smith as
our season is not long enough for it, but cortland and red delicious are both very vigorous varieties. Years ago I worked at an orchard with red delicious on M26 and was surprised to find them 12' tall! Cortland on 111 and 106
was very tall too. Yet the jonathan on M7 was so wimpy we
cut them down as they runted out and never filled out the block properly. We ended up re-planting jonathan on 111
since such a wimpy grower.

M106 is very prone to collar rot in my area. I prefer M111. Perhaps not an issue in your area of the country.

Most orchardists will use many types of rootstocks depending on the vigor of the variety. Usually varieties with low vigor or selections that are spur-type are put on
a more agressive rootstock.

Thanks for the feedback Spartan. I have two other apple trees from laurel bay on 111 and another from Henry Leuthardt on unknown. From my limited experience and others who have posted I do not believe root rot will be an issue. I think that i will chose a vigorous variety because when I cut the scaffolds and graft them I do not want competition for central leader. I Have 6 scion varieties:

gold rush
ginger gold
arkansas black
grimes golden
williams pride
gravenstein