I have a couple of TC blackberries that have been in large containers for a few years and I am finally ready to put them in the ground. I’d like to do some pruning of the root balls before planting but I seem to recall reading somewhere that cutting a root would cause a new shoot to grow and I really don’t want to encourage wholesale reproduction in the new location.
So is that right? If so, I’ll just have to dig really big holes…
Regardless what you do new blackberry plants will pop up here and there once in ground. also any roots that grew through the pot into the ground will create new plants.
Perhaps tip root a few canes for planting out next year and eventually scrap the potted plants.
Triple crowns can be expected to spread 15 feet, with new plants rooting where ever the canes touch the ground. I think that new plants coming up from the roots might be the least of your problems, as they can always be dug up. They are good sturdy plants, but I just thought it would be better going into it knowing what you are getting into. Best wishes.