I just get out and drive to as many local nurseries as possible. :) What I think is a good selection may not be what another person or an employee on the phone thinks is a good selection.

I check the big box stores too. I bought an Alpina 'Bluebird' at Home Depot earlier this year for ten bucks in a gallon that had at least eight vines. A great deal.

Donahues in in Faribault, which is only a couple hours from your area if I remember correctly. I have a family thing near the cities next year, and I am making a point of going to Donahue's.

They are a huge wholesaler of clematis, and have a retail area as well. I just noticed that they are closed for the season, but it's something to remember for next year.

http://www.donahuesclematis.com/

izzy,

The big boxes can be pretty hit or miss with regards to quality. Donahue's is probably a good bet but if they're closed you might also have luck with these:

Clematis in Minnesota (It looks like they don't have any local nurseries that specifically carry Clematis (Ill bet a bunch of them do though), but if nothing else its a list of local nurseries you can try to contact.)

Linders in St Paul (Local for you? They have some clematis listed on their site)
Hope that helps,

Eras