Delphinium elatum (common names: Delphinium)

I have a question of other gardeners about delphiniums.

The best delphs I've ever grown, I grew at 50 degrees north latitude...(in Ontario, Canada, that's at the tip of James Bay). my friend told me of a derelict farmstead that had existed on the banks of the Moose River which was being eroded away. There were delphiniums growing there that had naturalized themselves. The winters are long and extremely cold with little snow cover and the spring summer and fall are fickle, weather-wise. the farmstead was on the riverbank, 12 miles from the mouth of the river emptying in to James Bay. Beluga whales calve at the mouth of the river and seals sometimes visit the wharfs. It is the land of ice roads and freight canoes.
The delphinium roots I transplanted to my backyard grew to 8 ft tall and with minimum setback from transplanting.
The second year I split the clump into three...and they all flourished. When we moved south I did not bring any of the roots, but thought that a delph is a delph. Right?
Wrong. The delphiniums I have in my garden do well until the heat of summer...then they go into decline and only perk up near the end of October! Then they try to bloom again, just as November rolls around. I think I may have to make a trip back just to get some seeds...lol.
So, I need an expert... is there a delphinium expert to help me? Should I plant them, like foxglove, in semi woodland shade?

Mostly Magic Fountains series which we grew from seed, but also got a tall unknown dark blue at the Fife Show in 2005. And I rescued another mauvish-blue variety from a bargain stall at a diy store.