Another example, Mel suggests planting 9 spinach plants in each 1 foot sub block. Therefore, if you planted an entire 4 foot main block in spinach you would have 144 spinach plants. It does require that your soil be in tip top condition - lots of organic material in it and a strong desire to keep adding organic material. A real plus is the virtual elimination of heavy ground breaking activities once the garden is established. Square foot gardening requires that you keep an eye on the water needs of each block.
Close planting tends to deplete water very quickly.
On the plus side, watering the garden is a snap because of the small amount of space involved.