I transplanted the apple tree last week. It has obviously outgrown it's tiny pot. I probably should have moved it earlier, but I don't think it will have any problems going forward.
The apple tree had been kept indoors at a southerly facing window and was well acclimated to it. I'm attempting to harden it off by keeping it out doors in a place with mostly shade all day. I'll gradually move it to more and more sunlight.
The pot is filled with a mix of compost, seed starter mix and top soil. Once in the pot I watered it thoroughly.