Last year I had a couple of females that were only 1 ft apart. I got about an ounce of dry bud from each plant. I had one in its own hole, and got 5 ounces from it. So you can put them close, you just want get as much. At least that's how it's always worked for me. 2 plants 1ft apart = 2 ozs. 1 plant by itself in 2 ft hole = 5 ozs. Your choice.