When I was a lad, my old man told me that purple loosestrife was weed and that the RCMP had burnt as much as they could find just after WW11 as returning soldiers would have been introduced to weed in various theatres (they actually did burn weed - the weed had been bought by the French Settlers for making rope, clothes, etc). Of course, being curious I smoked some. I became rather ill and my old man had a good laugh when I arrived home.