goldfinch4 (Chris) lives in zone 4.
This is the first crop of chicks from Korspel Sport, I put them in end of last Oct. Put them on your wish list for later this summer. I will have some then. None are mature enough to ship yet. The only one right now that is mature enough to send is Semp. tectorum, and they are very hardy and tough.
All you need is good drainage, if you don't have that you can do pots or amend your soil. Sport is a tiny one, but very cute. : ) It seemed to make it through our weird winter weather (10 degrees with no snow cover) in Dec. Then we had cold and torrential rain. The rain is what will really do them in if you don't have good drainage. Other than that, they are very tough plants.