This looks like Eupatorium. And more specifically, Eupatorium cannibinum E-Flora BC Atlas Page (which suggests that this European species is spreading)
Or Joe Pye weed?An escapee from a nearby garden? It's growing wild along the banks of the Alouette. Eutrochium purpureum
Ah yes, that's the new name. I was trying to recall it, but E-Flora BC hadn't updated. Anyway, I don't think it is that one specifically, as the leaves should be whorled around the stem. In your photo, the leaves are hanging down on one side of the stem in groups of about 3.
Definitely not Eutrochium purpureum. Likely, as Daniel Mosquin said, Eupatorium cannabinum, or some kind of hybrid.