Actually, John Jeavons recommends having the leaves of your plants - all plants - touch at maturity. This helps to keep the soil moist, and holds down weeds - creating, as he calls it, your own micro-climate. The only problem I've ever had with this approach is that it creates TONS of diseases on my tomatoes. So now, I plant them three- four feet apart. Much better! It just goes to show - all gardening/farming is experimentation. Robert.