Since only marginally hardy for your zone (as with most other evergreen species), I doubt it would pose much of an invasive threat. Where have you found this plant in the US?

Gardengal...I saw it on e-bay from Brushwood Nursery. I asked Dan and he wasn't positive because I think he just started growing it . He is in Athens GA which is close to me but I don't think he has over wintered it yet. Just was afraid it would react like Sweet Autumn does here. thanks bobby