I read it's perennial... but not in which zones- so that means squat...
nothing is perennial in every zone.
I'm 6b, but that's not really reliable where I live. I could throw a rock out by bedroom window and nearly hit the Hudson River where it meets the Long Island sound at the head of manhattan. I also get a lot of deep hard cold blowing down from the Great Lakes and a lot of Caribbean warm water coming up from the Gulf Stream so every winter is different.
