They will even proliferate in zone 6 . Just let the seed heads ripen and then treat it like a salt shaker. Shake them out wherever you want more. The seedlings will however revert to the basic orange in a few generations.
During hot summer months they go dormant then in the fall they start to grow again. They will almost disappear during the summer (think daffodils.)
I can't stop the things from multiplying! I planted6 of them 2 falls ago and now I have too many! They were supposed to cover my fading daffs and now they are crowding them out. I'd say they do quite well in zone 6.