I planted 2 rows in a 4' x 36' raised garden. The plants were 24" apart and they were touching each other by the end of the season. I was happy with it though and plan to keep them at 24" for this season. IF you have the room a bit more would be nice and if you don't have the room 18" would be a tight fit but probably doable. So for every 10 plants in a row, you ideally need at least 2' x 20' or 40sf.