Unknown rootstock - fruit trees

[Forage420]

Hello,
I am on a committee for an allotment site and some people have applied to plant fruit trees. They have had the trees for some years in pots and cared for them on their patio at home and now they would like to enjoy them on their plot. There are rules here and some rootstocks are not permitted, but how do you know what rootstock a tree is? I have considered waiting until they come into leaf and using a phone app to see if it will make a suggestion on the rootstock, but I have a feeling it will only identify the type of fruit tree it is. Obviously it's important because on small plots you don't want to be planting trees that will grow to shade everything. I personally don't have an issue with trees being planted full stop, but there are rules here, and I would like to help these people as best I can.

[nickdub]

The only sensible compromise suggestion I can think to make is to allow the planting of the fruit trees, but on the proviso that if they exceed a specified height in future years, eg 12', then they will either have to be pruned back or dug up.

Virtually impossible to say by looking at a fruit tree grown in a container what rootstock it is on, unless it is specified on a label.

[Forage420]

Fair enough, thanks for the pointer

[Plot70]

I agree about the height and shade.
We just have a minimum distance from a boundary for new plantings.
There are one or two existing trees on boundaries that have been allowed to stay as they were planted before the current commitee .took over.