I have all but one of my plants in half wine barrels. This is year three for three of them and year two for three others. I have one in the ground that is five years old.
I find that the one in the ground is harder to control then the potted plants. I have to keep a close eye on the runners. They will pop up a long way away from where it is planted.
The three year old are doing well. The runners get to the barrel edge and then up. Easy to cut off or pull up and have replanted a couple. (Don't know why. Don't need any more
However, I did notice that the drain holes that I drilled in the bottom of the barrel now has roots into the ground. I decided that if I ever move I may want to take these plants with me (that is if the buyers don't wish to have them) so I will have to some how get under and cut these anchors.