They haven't been reliably persistent for me in the past...I bought one this year again...and it's still here...though I think the fall rains aren't kind on it.

I tried Colorado Gold several years ago. It did well that summer. I had high hopes, had ammended my normally clayish soil and planted it on a slope to encourage better drainage, but it didn't make it back the next spring. I think it needs drier conditions than I can give it, so I haven't tried it again.

I've gotten them to survive winters in zn 7 if they were planted on scree. The problem is, even planted on scree, a heavy enough rain storm at any time of year, but particularly summer, will cause them to rot. Even the summer rainfall parts of South Africa tend to have very consistent rainfall - not too much, not too little - as you'd expect for a quasi-maritime climate. And they are dry in winter. (and at the high elevations where plants like that are from, always cool at night)

Thanks for all the replies!

I'm guessing I won't need to worry about the invasive factor. We have such wet winters here that I doubt I'll even see it again next year, lol.
CMK