Tom,

I started C. lanceolata and clematidae from seed last year and they spent the winter in a nursery bed. It's too early here (I'm in zone 4 too) yet to know how they will overwinter, though the person I got the lanceolata seeds from is in zone 5 and has grown it successfully there. I'll try to let you know how they come through.

kms

The American Hort. Society encyclopedia says zone 7-9 for all Codonopsis, including C. ovata. On the other hand, I found a web site that says zone 4.

If you're looking for an inexpensive way to try codonopsis, Codonopsis clematidea is very easy to grow from seed. I got seed from the Rock Garden Society seed exchange, and, two years later, I had plants in bloom.

Good luck,
Janet

Here is a link that might be useful: Codonopsis ovata