Jelitto sells the seed, and they call it zones 6-9. I haven't grown this one, but I trust them for their accuracy in plant descriptions.

A dandy alternative to an above-ground container is the pot-in-socket technique.

You bury the socket where you want it, in the garden/landscape. Grow the tender plant in a pot which fits the socket. Pull the pot from the socket for wintering over. Easy-Peasy.

Great suggestion Don. That reminds me of the pot in pot method many nurseries use to grow trees. I think I will probably resort to using this method until I can harvest some seed of my own or divide the plants. Once I have multiple clumps I won't feel so bad if I loose one to a hardiness test.

Mike

I use it for annuals, and for growing perennials on.

Use copper-treated spin-out fabric between the two pots, and you'll eliminate a lot of problems with roots growing from the pot through the socket.