Not hardy, although if mulched heavily it may come back from the roots. It will bloom in one season from seed if you have early warm springs and lots of hot summer weather. It has been declared a noxious weed here, and is no longer allowed to be sold. It is also a pest species in Florida and South Africa.

Actually I have found that this IS hardy here it is deciduous but never even dies back survived 2 winters now including last winter with a low to 18-19F

I have grown this is 8a. Sometimes it comes back, sometimes it doesn't.