Toni
In the database, Black Adder is hardy to zone 4a
Anise Hyssop (Agastache 'Black Adder')
I thought it was hardy to zone 5, but since you're zone 5, it should be hardy for you.
The bees and butterflies love Black Adder! I love it also!
I have 2 or 3 plants in the ground and 2 in a large container tub (with Agastache 'Summer Breeze').
Make sure you cut the blooms off when you plant, so the plant can put all its energy into making roots.