Their mature spread is about 5' or even more, so you need to leave enough space for them. I think that as they are such 'architectural' plants, they look better planted singly, but you did ask!

My 2 are together Spritz about 4-5 apart I love the back drop they give to the plants in front, the bed is about 15ft wide by 12ft. I agree they need space to show off Lol.

That's fair enough, Denise! Everyone has their own ideas. That sounds lovely. :-)))