I recall reading that size of tree can vary by geographic location ( such as northeast US vs Western US )
Is there a generally accepted rule regarding the size a tree is capable of growing based on its geographic location, rather than simply root stock choice, and what fruit tree varieties does this apply to if not all?
Rootstock determines size and geographic location determines rootstock used YES
Experiments with the Geneva rootstocks prove they don’t grow to the same size tree in all parts of the US.
I don’t think there is a rule really. Partially because it varies with the species of tree. The rootstock is used to control tree size. Dwarfing rootstocks reduce tree size and produce smaller trees with a given scion (cultivar). But scion vigor also has a big effect on tree size. Honeycrisp is a weak grower and produces a small apple tree while Bramley is very vigorous and produces a big tree. Soil type will also effect tree size.
In general if you keep the dwarfing rootstock constant-
More annual rainfall means a bigger tree.
Longer growing season means a bigger tree.
Trees at the edges of the natural climate range (or beyond) of the tree or rootstock will be smaller.
For apples-
Out West the trees on dwarfing rootstocks are smaller than you would expect from the literature.
For sweet cherries-
Out East the trees on dwarfing rootstocks are smaller than you expect from the literature.
Other species of fruit trees will be different.
It would help if you let us know what species/cultivar/rootstock combination you are interested in and what state you are located in. With that information we could give you more useful advice as far as tree size.
Areas with more rain and good soil will grow bigger and better than a lack of. So in a way, yes.
I have a variety planted / on order
NE OH
Soil is mostly clay below 4-6 inches of dirt
Peach on Guardian
Plum on Marianna2624
Apple on m-111 and g41
Cherry on mazzard
Cherry on G3
Persimmon that say they grow 10-12-15 ft
The apple trees will be normal as far as size in your climate and will follow what you see in the literature, G41 dwarf, M111 semi-standard.
The cherry on mazzard will be a full sized tree since it’s a standard sized rootstock. The cherry on Gisela 3 I assume you want to purchase from Raintree nursery and it’s a sweet cherry. This tree will be smaller than the literature suggests. It may be too small for your needs possibly. Gisela 3 is pretty small in the first place and under Eastern conditions it will be smaller still. You want to be careful to meet its needs and protect it from animal damage. It doesn’t really have the vigor to bounce back from animal damage. I think Gisela 5 is probably a better choice if you haven’t already purchased a tree.
For the other species of tree I have no idea how the local climate will effect them.