namnhi, . How do you get your into the flat pot without killing it? Do you go slow over a few year or in one go?
Depending on the size of the the root. With 5 and 7 gallon cans, I think you need to transplant them to less smaller pots at first and 2 years later, you can put them into the smaller one. If I was you, I prepare 2 pots with different sizes: small and big. During the transplant, I would know which pot is suitable for the tree based on its rootages at that time.
When did you do it? After flower faded?
No. With the deciduous flowering or fruiting species, we should transplant them when they have no leave. The best is in end of the fall. Because we can mess around of the root system at that time and the trees doesn't care much due to dormancy. It is alike when the surgeon wants to perform appendectomy for his/her patient, the pt has to put into deep sleep (general anesthesia). Same principle. It is why Home Depot, Lowes always stock their deciduous fruit or flower trees in the fall.
Bonhe