nicotiana mutabilis

I was given some of these late in the season and they're obviously not going to get to flowering before the frosts. Are they annuals or tender/half hardy perennials? If I dig one up and bring it into a cold greenhouse might it survive long enough to give me some seed? or will I just have to buy a packet next year.

They are half hardy annuals and I fear it's too late. Buy a packet next year. They are lovely.

Thanks B-L. I saw some in flower in a friend's garden today, I hadn't realised they were so special.