Cut back the dead stuff for neatness sake but it has no effect on the plant. It's bone hardy and should start sprouting if it's survived the harsh winter you had over there. I don't know when it should start in your zone. Here it's already 8 inches high.

Depends upon on the brutality of your winter and where the container was. In my zone, it comes back. It sprouts all new growth so last year's dead plant growth can be removed safely.

FataMorgana