I transplant 2 or 3 times before they go into the final pot which is usually a 4gal pot. Each time I saw the bottom inch or so off the rootball with a bread-knife to get rid of any stringy roots. If there are roots wound around the sides I slice them off too.
It’s kinda like the idea behind those airpots that trim the root ends and cause branching of the roots to get a lot more fine feeding tips growing. I always notice a spurt in plant growth shortly after and new roots will be poking out the bottom of the pots in a few days.
