Apple tree - M26 or M106?

[Maggiethecat]

At the garden centre going to buy an apple tree. Ideally would want an M 26 rootstock although my garden could take a M106 but would prefer the smaller tree.

They only have the one I want in M106 and I wonder if it’s okay to get that and just keep pruning to keep it on the smaller side?

Pruning to keep a standard tree smaller doesn't really work, as the harder you prune the more it will grow and you have lots of water shoots to contend with and little fruit ( especially so if it is a tip bearer). However if your soil is poor, a MM106 might not grow as big as one on more fertile soil. Have you looked at any of the specialist nurseries, e.g, Orange Pippin Trees or Frank Matthews? You could control the growth if you were going to treat it as an espalier.

Good that I went for the smaller one!