First of all, “weed” is in Norwegian “ugress”, not pot or that kinda stuff. Was watching a tv program about Mongstad and the flora at the industrial area. There they had cut down 10.000 picea sitchensis (sitka-gran) in one weekend. If the tree strike root it will cover the cultivated landscape in just a few years.
http://www.miljolare.no/data/ut/art/?lang=eng&or_id=4459