I would not expect Concord to suit zone 5 (quality seems to be sensitive
to season and growing conditions even here in the Niagara Peninsula -
7a?),
Concord has been one of the major grapes grown in the Finger Lakes (NY) since the late 1800's; and is considered one of the hardiest grapes usually grown here. Although some of the newer maps show this as zone 6, the pre-climate-change maps showed this as zone 5.
Grapes in this area (Concord and others) are grown near the lakes themselves; up in the hills far away from the lakes is considered too cold. So there is certainly some microclimate effect. But some areas up in the hills are, or used to be, zone 4. I have known Concords to bear quite well after winter temperatures well into the zone 5 range (negative teens F) in the specific area of the vineyard.
Does Canada use the same zone designations as the US? Maybe that's the complication. I thought zone 7 started somewhere down around Virginia. -- I see that newer maps show some zone 7 in Pennsylvania. But Concord has been grown here since long before the warming.
--Rivka
Finger Lakes NY; zone 5 mostly, late 1900's -- maybe now it's 6