Square Foot Planner

Square foot gardening is a method of growing food in raised beds divided into a grid of one-foot squares. Each square gets a specific number of plants based on the mature size of the crop. A tomato gets one square to itself. Carrots fit sixteen in a single square. The grid eliminates the guesswork of row spacing and makes it possible to grow a surprising amount of food in a small area.

The method was popularized by Mel Bartholomew in the 1980s. The core insight is that traditional row gardening wastes enormous amounts of space on walkways between rows. In a 4×8 raised bed with a grid, every square inch is growing space. The walkways are around the bed, not inside it. A 4×8 bed using square foot spacing can outproduce a 10×20 row garden because more of the area is actually planted.

A physical grid template that sits on top of the bed is the single most useful tool for square foot gardening. You can make one from wood strips, PVC pipe, venetian blinds, or string, but the hard plastic commercial grids are worth the money if you plan to use the method across multiple seasons. They do not rot, they snap together, and they stay square.

The grid does two things. First, it physically marks where each square is so you are not eyeballing spacing. Second, and more importantly, it changes how you think about the bed. Without a grid, a raised bed is one big planting area and the temptation is to crowd things in. With a grid, each square is a decision. One tomato here. Four lettuce there. Nine onions in that corner. It forces you to plan, and planning is the difference between a bed that produces and a bed that turns into a tangle by July.

Companion planting has a reputation problem. Most of what circulates on the internet is folklore passed from one blog to the next without citation. “Plant basil with tomatoes” is everywhere. The reason why, and whether it is actually supported by research, is usually missing.

The truth is that some companion planting relationships are well documented and others are not. French marigolds suppress root-knot nematodes in soil. This is not folklore. It has been demonstrated in controlled studies at multiple universities. The active compounds in marigold roots are lethal to nematodes, and the effect persists in the soil after the marigolds are removed. That is real.

The Three Sisters planting, corn, beans, and squash, is also well supported. Beans fix atmospheric nitrogen and make it available in the soil. Corn provides a physical structure for beans to climb. Squash shades the ground, suppressing weeds and retaining moisture. Each plant contributes something the others need. This is intercropping, and it works for documented reasons.

On the antagonist side, alliums (onions, garlic) inhibiting legume growth is consistent across sources and is attributed to allelopathic compounds. Potatoes and tomatoes sharing disease pressure is basic plant pathology: they are the same family and host the same pathogens. Dill inhibiting tomato growth when mature is documented, though dill at the seedling stage may actually benefit tomatoes by attracting beneficial insects. Context matters.

The companion data in the planner above is limited to pairings that have research or strong extension-service support. If a pairing is not listed, it means the evidence was not strong enough to include, not that the pairing is neutral. The absence of data is not the same as the presence of proof.

The spacing numbers in the planner come from the square foot gardening method and are based on mature plant size. One tomato per square foot is tight. It works, but only if you are aggressive about pruning suckers and using a cage or stake to keep the plant vertical. If you let a tomato sprawl, it will take over three or four squares and shade everything around it.

Vertical growing changes the math. Pole beans at eight per square foot is dense, but on a trellis the canopy is vertical and the ground footprint stays small. Cucumbers trellised vertically fit two per square instead of one. Any vining crop benefits from growing up instead of out, and in a small bed it is often the difference between fitting three crops and fitting six.

Succession planting is the other lever. Radishes are done in three weeks. Lettuce in six. When a fast crop finishes, that square is open for something new. A single 4×4 bed can produce three rotations of fast crops in a season if you replant promptly. The grid makes this obvious: when a square is empty, it is asking for something.

In a row garden with wide spacing, companion planting is a nice-to-have. The plants are far enough apart that antagonistic effects are diluted by distance. In a 4×4 raised bed, every plant is a neighbor. The root zones overlap. The canopies touch. Allelopathic effects that would be negligible across a ten-foot row become significant across a twelve-inch square.

This is why the planner flags both good and bad pairings at the neighbor level. If your tomato and your potato share an edge in a square foot grid, they share disease pressure in a way that two plants twenty feet apart in a row garden would not. The tighter the space, the more your planting decisions matter.

The first mistake is ignoring height and shade. A corn square on the south side of a 4×4 bed will shade everything north of it for most of the day. Put tall crops on the north side or the trellis end so they do not block sun from shorter neighbors. This is basic geometry, but it is easy to forget when you are focused on spacing numbers.

The second mistake is underestimating squash. Summer squash and zucchini at one per square foot is technically correct, but a healthy zucchini plant will sprawl well beyond its square by midsummer. If you are planting squash in a 4×4 bed, put it on a corner so it can spill over the edge instead of smothering the carrots.

The third mistake is treating the bed like a permanent installation. A square foot bed is a living system. Crops finish, squares open up, and new things go in. If you plant the whole bed on the same day and harvest everything at the same time, you are leaving months of growing season unused. Stagger planting dates, replant empty squares, and treat the bed as an ongoing project, not a single event.