@aaCharley
Welcome to the Agastache and Salvias forum!
I don't know, as I've never had Black and Blue overwinter here, but then I usually have it in containers in my zone 6a yard and they die with the frost/freeze each year. Are yours in the ground and mulched that overwinter?
@FBTS would you chime in regarding his question please? Maybe some other members who had it overwinter will chime in also.