Answer: You will stress your plants much less if you move them in the winter while they are dormant. At that time you can cut them down to a more manageable size and dig them up without worrying too much about cutting back the root system. If you move them while they are actively growing they will suffer some transplant shock but they should survive the move. Start by cutting everything back so you can easily handle the shrub, then dig down, expecting to find the majority of the roots in the top 18-24 inches of soil and radiating out at least as far as the longest canes. Try not to sever any of the large roots when you dig. How large a container you will need really depends upon the size of the root mass. A half whiskey barrel is fine for a large shrub.
Good luck with the move!
Q&A Library Searching Tips