Winter Veg and Nut Trees in North USA/ Canada

Ok maybe this is the wrong forum but when I went to Great White North it seemed to imply events, resources etc. But also, maybe you north of USA folks might be able to help....

We have just had a wonderful WWOOFer stay with us and she's going back to Canada mega inspired (!!!) but there were two areas that I couldn't help her in. I didn't know if there were any veg that would grow through the winter (she's in Calgary) nor did I know of any nut trees that grow there.  Can anyone help me/her?

if you have a greenhouse or hoophouse you can grow some greens like spinach, chard, lettuce etc in the winter..i do here in my greenhouse zone 4..also depending on zone you can grow walnuts of all kinds, sweet chestnuts hazelnuts, hickory, beech, and possibly Halls Hardy almond

http://www.sln.potsdam.ny.us/ might be able to help with the nuts/trees portion of that.