We found a farm/nursery near Barrie that grows native trees and they do it beautifully!
We are trying out some of their trees that are on the borderline of surviving in this zone. We are between 4a and 5b zones here but some trees for zone 4 have a hard time, probably because of the erratic freezes and thaws. This year we planted 2 Black Walnut trees, a Bur Oak, a Red Oak, (the oaks should be OK here) and really stretching it with a Tulip Tree. Steve says he has never seen one north of Hwy 7. We will see! Also 6 Tamaracks which should be fine here.