What you saw may have been hemp, not pot. I don't know about OR, but I've been told that in WA the law says pot being grown outdoors can't be visible from the road. There are 3 or 4 farms in my area and they all have fencing that blocks the view from outside, so it could be true. One of the farms has plants that are currently taller than the 8' fence, so you can see the tops as you drive by, but the rest is blocked.