If you have spots picked out you can plant them and graft onto them next year. Or 5 gallons should work. You can then graft onto them and plant them if grafts take.

Thanks -- I don't have spots picked out and will probably give away most of the trees next year, assuming the grafts work out, so five gallon buckets are the way to go... if I can scrounge up enough.

Just be sure to bore holes for sufficient drainage, and use potting soil. When I have tried to skimp and use garden soil it hasn't worked well. Potting soil will be fine for rootstocks for a year, but after that it is wise to consult the container forum. Also, the pots will need to be buried during the winter,