A number of years ago I read a fascinating article about an old CPR nursery in Strathmore, Alberta.  It's many years ago that I read the article but if I recall correctly, apparently it had long been abandoned and was due to be developed when someone called in some experts and apparently they were somewhat surprised to find trees and shrubs growing there that had pretty much been written off as not hardy for Alberta.  I'd love to find a link to that article.