Grow outside? Completely natural without buying pesticides, oils, etc. Also would placing several seeds in one hole make one hard-core extra beefy plant. Only unnatural thing I'm considering is growth hormones. If so, where to get them?
I would consider just growing one plant per hole. otherwise your going to see a drastically reduced harvest. Make sure the soil is good. Growth hormones? I would just use nutrients, most of them are basically just decayed plant matter.. arrive never even heard of growth hormones for pot.
Growth hormones are becoming a fad because they can make plants surpass their genetic limits. As for where to get them, try google, because Im not really sure. A bit of advice on hormones from the pros though. "If you cant grow a good plant without growth hormones, you cant grow a good plant with growth hormomes"