You can maximize the productivity of the garden using intensive gardening techniques. Three ways to garden intensively are spacing plants closely together, intercropping, and succession cropping.
An intensive garden is possible in part because, with a few exceptions (among them strawberries, asparagus, artichokes, and most herbs), the food plants are annuals. You sow the seeds, harvest the plants, and finally rip out the roots, often leaving space and time for one or two more crops in the same season.
Intercropping pairs fast-growing with slow-growing crops in the same row. As the first crop matures and is harvested, space becomes available for the second crop which is beginning to fill out. The combinations of vegetables are almost infinite; any small, fast-growing vegetable can be intercropped with almost any slow-growing larger one.
One pair that go well together are radishes and carrots: The radishes are ready in three to four weeks, just as the carrots begin to fill out. The carrots remain in the row 90 days before they’re ready to pull. Sow lettuce among rows of almost any larger plant, beans for instance. As the final lettuces are harvested, the beans begin to take over the space. Pair onion sets with any long-standing plant, and pull for use as green onions to make way for the later crop.
In this approach the soil is never without a crop. As soon as one crop, or a portion of a crop, is harvested, another is sown. For instance, as you harvest radishes planted in early spring, sow the empty spaces with squash or beans. Follow the peas you plant in early spring with spinach, a quick cool-season crop. A typical succession begins with radishes and lettuce, then snap beans, and finally winter carrots.
In another form of succession planting, sow seeds in small successive waves planned to produce a season-long harvest of a single type of vegetable. You plant the second batch before you harvest the first, and the third before you harvest the second.
Follow a small March sowing of cold-hardy lettuce with a second set of lettuce seeds a couple of weeks later, then more two weeks after that. The lettuce will ripen sequentially, giving you a steady harvest of lettuce for months. For a small family, this is a wise approach. One long row of lettuces maturing all at the same time is more than most families can consume.