Thapranksta:

Your question is a bit difficult as most orchards do not plant all their apples on one rootstock. Often they use several different ones based on what was available when they bought the trees, what pruning/spacing system they wanted for that orchard block,ect.

Sometimes hardiness is an issue. For example hardy standard rootstocks (antonovka, prunifola, ranetka ect) are
necessary in super cold regions such as ND,SD, WY,MT ect.

Most other areas abandoned standard rootstocks years ago as
they grow too tall to easily prune/spray/pick. Easier with
dwf or semi-dwarf rootstocks. Often spur-type or low vigor
varieties (Jonathan) need to be on a less dwarfing rootstock or they runt out and never amount to anything.

I hate the terms dwarf or semi-dwarf as too generic. Orchards years ago in WI where I live switched to using M7
as semi-dwarf and free-standing, however they pruduce tons of root suckers. Now the hot rootstocks are Bud 9 & Nick 29 but these trees must be staked for the life of the tree.

M26 is still used (8'-12' tall trees) but more prone to
fireblight and can tip in heavy clay soils.

Every rootstock has advantages and disadvantages depending
on climate, soil type, low density planting or high density
planting (Tall spindle) ect.

My 17 tree hobby orchard has apples on M7, MM111, and yes even 4 on a standard rootstock. I vase prune heavily on some for height control. Others seem jsut fine. My site is weird as very low nitrogen levels. I have to fertilize
heavily on new trees and even lightly on old ones or the
leaf color is poor. I find my apple trees do not grow as
tall at my site as other sites I have grown at. Hence my
need for more vigorous rootstocks.

Nobody can make you a good suggestion unless we know what soil type you have, are you willing to stake each tree
permanently or want free standing orchard ect. Can you provide more information?

When you do purchase your trees, watch out! Many mail order and almost all retail outlets will either list them as dwf, semi-dwf or no listing at all. Always ask what rootstock they are on. Don't buy if they can't tell you.
A Mcintosh on M26 will be quite shorter than one on MM111.
You cannot properly space your trees if you have no idea what rootstock they are on.

In fact, one mail order place I called had Cortland on two different rootstocks. After the trees were harvested, they are all mixed together since both rootstocks are "semi-dwarf". Big difference though when some were on M7 and others on Bud 118.

Yeah, just as I figured the subject of rootstock can turn into an even more complicated matter. I have actually called places and asked what specific rootstock they have - I find it very odd that you do have to call them. Some places are specific in what they carry right on the websites.

I would rather not have to stake my tree. If I prune properly do I still have to worry a lot about planting distance with different rootstocks? I haven't really inspected my soil yet but if I had to guess from how long water stays around after a rain, I would think it is very clay-like.

Thanks.

Thapranksta:

I am not familiar with Tenessee so perhaps someone more local could advise best on what rootstocks work in your area.

I can personally say that M7 does well in heavy clay soil and is a free-standing tree. Years ago when I worked at a
commercial orchard we spaced our trees this way:

M7 rootstock.....15'-18' apart. Trees will just touch
at 15' apart when full grown.

M26 rootstock.... 10'-12' apart and STAKE.

standard rootstock: 30' apart
MM11..............18' apart

I can add that bud 9 and nick 29 can be grown 8' apart. All of this is just a guideline and YEs pruning will definitely determine ultimate size of tree. However, I find that rootstock and vigor of scion variety play a more
important role in ultimate size.

For heavy clay soil, I would use apples on M7 or M111 based on my experience (for a free standing tree).