In your zone I'd plant them in the ground and let them be. They can be kept inground all they way to zone 7b. They'll die back in the winter and return from the roots in the spring. Just feed them often during the growing season.

You can add mulch in the fall, this will help keep the roots viable even in a freeze. This works with all tender perennials just to help keep the soil insulated.

Thank you both for your advice....The brubs are already in the ground, so I will mulch them. :)