They are a hardy plant,--you can winter them over in the bucket OR if the ground is not froze, plant them directly in now! Sis replants them all year long and they always grow for her! lol!
Ya, it takes several bushes to get many berries.
Some people south of us here have 10 acres of commercial elderberries growing and they harvest them by hand and make juice that is sent out somewhere.

"A machine you build yourself is a vote for a different way of life. There are things you have to earn with your hands."