I have a clump of Cosmos atrosanguineus in my I think USDA 8 zone in inland Australia and despite drought,frosts and whatever else happens weather wise this continues to grow and expand producing masses of chocolate scented flowers.Its a real joy and I can't imagine my garden without it.It does get a bit mildewy towards winter but that is its only fault and that isn't a problem as its time to cut it back anyway, Lyn Edwards Canberra