The plant that you did not plant that is doing better that the one you did is a weed. This means that it is possible that one man's weed is the next girl's desirable plant.
And this opens the field to relativism, not to mention infestation.
My neighbour Len insists on planting Statice where I am trying to grow Kangaroo Paw, his is doing better than mine, but is his a weed?

Many years ago when I went to The Flinders Ranges for the first time the hillsides were covered in purple and scarlet, beautiful, I thought.

Michal Kluvanek