Well..if you trim the huge ones they will be shrubbyier.If were planted close I imagine could grow as hedge if that was an a idea.They all grow a lil different and also depends on the soil.the richer& moisture the better it is.
I don't have any grown together,but have thought about it.I have a few stand alones,but most are like a backbone stuck here& here& there.I had one grow 10 ft this year....and next year I'll keep that one shrubby.The 1st yr hubby "accidently" topped it in half when it was just reaching 2 ft.I actually liked the way it grew that way better.It had alot more flowers,but we were dryer this year also.