If we plant in rows, using traditional spacing, yields of these common vegetables is relatively low in a 4'x4' bed. At this level of production, it's no wonder so many home gardener's say it's not worth it. However, if we discard planting in neat rows a foot apart, we can produce as much as 3 times the yield in the same space! And since we're working in a 4 foot raised bed, we don't need rows to walk (or run equipment) through; we can reach those plants in the center perfectly well.
Lets also not forget, we can plant even more if we intend to harvest some young plants. Onions and spinach in particular can be planted at twice the rate shown above, and harvest every other plant for eating when young, allowing those left to grow to maturity.
Notice on the left the already more than tripled production when we stop planting in rows, but we don't need to stop there. Because young onions and spinach are so much smaller than mature plants, they can be planted with only half the distance between plants. Then, as they mature we can selectively harvest as shown by the outlines in the right picture to allow those remaining plants enough space to grow to maturity.
The effect of this type of planting is two fold. First, it allows us to have twice as many plants in the same amount of space, effectively doubling our harvest. Second, because the plants are spaced much closer when small they will quickly shadow any weeds that might try to grow between plants preventing them from taking root thus decreasing the need for weeding.
So many home gardeners find themselves plagued with low yields and heavy weeding. That's because the traditional methods of planting seeds aren't designed for the home garden. When we rethink how we plant and harvest our garden we can double, or even more than triple the harvest without a need for increased garden beds. And in the case of spinach and onions, we can reap more than 5x the produce by interspersing our baby spinach and green onions with those plants we intend to allow to grow to maturity. And we can do all this while decreasing the time invested weeding our beds. It doesn't get any better than that!
Let's get planting!