If you're working with a small garden — under 200 square feet — every plant is a decision. A single corn plant takes up significant space and produces one or two ears. A single well-maintained tomato plant produces 10 to 15 pounds of fruit. The math is not complicated but it requires actually doing it before you plant.
The High-Return Crops
Tomatoes produce more food per square foot than almost anything else you can grow. An indeterminate variety in full sun with adequate water will produce continuously from August through frost. One or two plants is enough for fresh eating for a family of four; three or four produces enough for sauce and canning.
Zucchini produces more food than most gardeners want, which makes it excellent for small gardens where high yield is the goal. One plant is genuinely sufficient. Two plants is plenty. Three is a mistake you'll regret by August.
Pole beans grow vertically and produce far more than bush beans in the same footprint. A 4-foot-wide trellis 6 feet tall produces beans continuously for 6 to 8 weeks. Bush beans produce all at once over 2 weeks and require more horizontal space for the same yield.
Lettuce and salad greens grow fast, can be harvested as cut-and-come-again crops, and are worth more per pound than almost anything you can buy at the grocery store. Plant in succession every 2 to 3 weeks for continuous harvest. They tolerate partial shade better than most vegetables — useful for spots that don't get full sun.
Herbs are the highest-value crop per square foot in any garden. A 4-foot square planted with basil, parsley, chives, thyme, and oregano produces hundreds of dollars of herbs at market rates over a season and requires minimal space and attention.
The Low-Return Crops to Skip
Corn requires a block planting for pollination (minimum 4 rows), produces one or two ears per plant, and takes up space all season. Unless you have room to spare, buy it from a farmstand.
Melons need a long hot season, lots of space for sprawling vines, and produce a handful of fruit per plant. Marginal even in zone 6. Skip in zone 5.
Pumpkins and large winter squash take up enormous space and can be purchased cheaply in fall. Delicata and acorn squash are more compact alternatives if you want winter squash without sacrificing the whole garden.
Vertical Space Is Free Space
Trellises, fences, and cages turn horizontal space into vertical space. Cucumbers, pole beans, peas, and indeterminate tomatoes all grow upward given support. A 4-foot-wide bed with a trellis at the back effectively doubles or triples the productive capacity of that footprint. If you're not using vertical space in a small garden, you're not using the garden efficiently.
Whatever you're growing this season — grow it well.