This past summer, cannabis just grew all by itself in my suburban backyard here in Eastern Ontario. I have a a tradition of taking the portable washing machine outdoors and making bubble hash on my deck every late fall when the temperature gets cool outside. So I routinely dump the washing machine leftovers over my outdoor no-till gardens - over the snow on top of it normally. Lol
I never noticed a seed, but I found a weed plant sprouting in early April (where I deposited the bubble hash waste the autumn before) during a freaky warm spell that lasted days. Of course the regular variable weather finally returned near middle week, and lasted a few weeks after. It survived a night of -6
° C (21
°F). It never reached above freezing for the next week or so:
So the weather got warmer and it survived and grew even though the wife and I had no plans to grow weed outside in the backyard or patio. I didn't have the heart to pull it out while planting vegetables, so we let it grow under the conditions I would not do anything to it.
Anyway, it took over my wife's herb garden area, and the trellis we had cucamelons growing. I never fed it, watered it (except for plants around it), pruned it, or anything. It literally grew by itself until harvest without intervention. But we never anticipated a 10 foot high, 12 foot wide tree. This is the girl in late summer (there are peppers in there too. Lol) She yielded over 3 pounds of really crystally bud:
Peppers can be a lot more finnicy than cannabis I'm starting to learn. They call it weed for a reason.