I have read about some success as a perennial in NJ on here with B&B, but zone 5 would be too cold for it to come back in my opinion. A lot has to be considered, such as placement (i.e., next to the house), drainage (as wet winters can increase the likelihood of root rot), and mulching. From what I have read, 20 degrees F and below is where B&B tends to die. If the bed is mulched thoroughly and in close proximity to a heat source, such as your house, the soil will be warmer than out in the open. The four Black and Blues I have were supposedly hardy to zone 8, so I have taken the steps outlined above. B&B is one of the more cold hardy guaraniticas, but anything north of zone 7 is pushing the envelope and you will likely have to plant every year.

There are a couple ways you could try overwintering black and blue. I know there are forum threads you can search for that will provide more details, but one method consists of digging up the plants, putting them in a black garbage bag, and storing them in your basement for the winter. The outside method consists of covering the garden bed with bags of leaves and then covering the bags with a tarp to keep moisture out. I will be trying one or both of those methods next winter. This week I will be buying my first black and blue plants. You can find them at nearly every garden center around here.

I am in zone 5 and I grew my B&B in pots and just brought them in and let them dry out. I rather treated them like dahlias. In late Feb. they started growing. I placed them in light and watered them. They are doing great and I even took a few cuttings already.