1 summer squash plant per 4 square feet, a 2 x 2 foot block with plants 24 inches apart. Summer squash is bush-type so the block holds the whole plant, unlike vining winter squash.

1 artichoke plant needs about 4 square feet, a 2 by 2 foot block, not the reverse. Extension spacing, growing it as an annual versus a perennial, and how long you wait before the first harvest.

Plant 4 shallot sets per square foot, 6 inches apart. Each set divides into a cluster of bulbs, so the count going in is sets, not the final harvest.

9 leeks per square foot, 4 inches apart, on a 3 by 3 grid. The real tradeoff is spacing versus a thick, blanched shaft: hilling or deep planting to blanch the stem, why tighter spacing means a thinner shaft, a long season from seed, and harvesting through cold weather.

1 sage plant per square foot, 12 inches apart, but sage is a woody perennial that grows 2 to 3 feet wide, so that one plant spreads well past its square within a few years. Pruning to keep it from going woody, replacing it every few years, and harvesting without stripping it bare before winter all matter more than the count itself.

1 rosemary plant per square foot, 12 inches apart, on both my chart and the Plan My Garden planner. That number is a starting layout, not a permanent fit: rosemary is a woody shrub that outgrows its square within a few years, is not reliably winter hardy in cold regions, and grows better from a cutting than from seed.