Square-foot gardening basics, six seasons in
The first raised bed I ever built was a 4x8 cedar kit from Home Depot, screwed together in my driveway in April 2019 with a cordless Makita drill and a lot of confidence that turned out to be misplaced.
I filled it with Mel's Mix following the recipe to the letter. Planted lettuce at 6-inch spacing because that's what I read on the back of the Buttercrunch seed packet. Forgot entirely about thinning. Showed up in June to about 120 spindly, pale lettuce plants in a bed sized for 32.
That was the year I learned what square-foot gardening actually is. Six seasons later, it's how I run every raised bed I own, and it's the starting point for almost anyone who's new to gardening and asks me how to begin.
The one-page version
Mel Bartholomew was a retired civil engineer who got fed up with traditional row gardening in the late 1970s. He watched people with a 10x20 plot rototilling rows 30 inches apart, then complaining about weeds, water, and yield. He started asking: why rows at all, if you're not running a tractor?
His answer: divide a raised bed into 12-inch by 12-inch squares. Use string or lath or chalk. Each square holds 1, 4, 9, or 16 plants depending on their spacing needs. One tomato per square. Four lettuces. Nine bush beans. Sixteen carrots or radishes. That's it. That's the method.
The first edition of Square Foot Gardening came out in 1981. PBS made a series. Millions of backyard gardeners adopted it. The third edition, All New Square Foot Gardening (published 2013), is still the reference I reach for more than any other garden book on my shelf.
Why the grid works
Traditional row spacing comes from farm-ag practice. "Plant 3 inches apart, rows 18 inches apart" is advice for someone with a tractor and 2,000 linear feet. In a 4-foot-wide raised bed, there's nowhere to walk, so the "rows 18 inches apart" part is wasted. You can plant the full width of the bed at the in-row spacing, in all directions.
A 12x12 square is exactly the right size to hold a uniform grid. Carrots are 3-inch spacing; a 12-inch square holds 4x4 = 16 plants. Bush beans are 4-inch spacing; that's 3x3 = 9. Lettuce is 6-inch; 2x2 = 4. Tomatoes are 12-inch; 1 per square. The math is deliberately clean.
A 4x8 bed is 32 square feet. At SFG densities, that's 32 tomatoes, 128 lettuces, 288 carrots, or some combination. Scale of production most people don't expect from that footprint.
Mel's Mix, and why you might want to skip it
The orthodox SFG soil is Mel's Mix: one-third compost (blended from five different sources if you can manage it), one-third peat moss or coco coir, one-third coarse vermiculite. Fill the bed, plant, done.
It works. It also costs about $200 to fill a 4x8x12 bed the first year because vermiculite is surprisingly expensive. For your second bed, third bed, and beyond, you can cheat. I filled my 2024 beds with Coast of Maine Bar Harbor Blend and topped with a 2-inch layer of my own compost. Worked perfectly.
The thing I will not skip: vermiculite in the first year. It's what makes the mix drain like potting soil but hold moisture like good garden loam. Substitutes (perlite, sand) don't perform the same.
The thinning problem
Here's what nobody told me in 2019: when the seed packet says "plant 2-3 seeds per hole, thin to one," that's not optional. The 2-3 seeds are insurance. You absolutely must thin, or all 2-3 will grow at the same stunted pace and produce nothing.
Thin when the seedlings have their first set of true leaves (the second set of leaves, after the cotyledons). Use scissors or a thin blade. Cut at soil level. Don't pull, because pulling disturbs the roots of the seedling you're keeping.
Eat the thinnings. Baby lettuce, radish greens, beet tops are all edible and delicious. In 2024 my spring salads were nearly all thinnings until the end of April.
What actually fits in a 4x8 bed
Here's a layout that has worked every year for me in Zone 6a:
- Four squares of tomatoes (4 plants, trellised, one variety each: Black Krim, Cherokee Purple, Brandywine, Sungold)
- Four squares of bush beans (Blue Lake, 36 plants)
- Four squares of leaf lettuce (Buttercrunch + Red Sails, 16 plants)
- Four squares of carrots (Scarlet Nantes, 64 plants)
- Four squares of radishes (French Breakfast, 64 plants)
- Four squares of basil (Genovese, 16 plants, mostly next to tomatoes)
- Four squares of spinach (Bloomsdale, 36 plants)
- Four squares of mixed herbs (parsley, dill, cilantro, chives)
Total: 32 squares, filled from ground to trellis, four or five harvests per season because the lettuce, radishes, and cilantro come out and get re-sown three or four times.
Where SFG starts to break down
Not every crop plays nice in a 12x12 grid. Here's what I've learned the hard way.
Corn. Corn needs block planting for pollination. A single 12x12 square holds 4 plants, but 4 corn plants won't cross-pollinate reliably. You need a minimum 4x4 block (16 plants). If you don't have room for that, skip corn in SFG and plant in a dedicated row bed, or a big container cluster.
Winter squash and pumpkin. These sprawl. A single butternut wants 4-6 square feet just for vines. Trellising helps, but plan on dedicating an entire corner of a larger bed, or a separate hill.
Indeterminate tomatoes. Mel's book says 1 tomato per square. That works for determinates (Roma, Celebrity). For indeterminates like Brandywine and Cherokee Purple, I've moved to 1 plant per 4 squares with aggressive single-stem pruning. Less disease, better fruit.
Potatoes. I've never gotten potatoes to work in a 12-inch-deep bed. They want 18+ inches and room to hill. Use a grow bag or a separate tall bed.
A 2022 bed that changed my mind
July 2022, middle of the Indiana drought. I had a 2x8 bed that I'd planted in May with a Three Sisters-inspired layout: corn block (4x4), pole beans climbing the corn, winter squash at the base. It worked. Barely. The corn ears were 70% filled (acceptable), the beans went crazy and yielded two full buckets, and the squash sprawled out the end of the bed but produced six butternuts.
What I learned: you can push SFG's limits in directions the book doesn't cover if you're paying attention. Mel wrote the method around home gardeners, not Indigenous polycultures. You don't have to follow the layout if you understand the spacing logic underneath.
Three things to do if you're starting this weekend
Build one bed. 4x8 cedar is the standard starter. A kit runs $80-120. Screw it together in an afternoon.
Fill with something reasonable. Mel's Mix if you can afford it. Fox Farm Happy Frog raised bed mix or Coast of Maine if you can't. Don't skimp.
Pick four crops max. Lettuce, radishes, bush beans, and cherry tomatoes is a perfect starter mix. Everything germinates fast, everything harvests within 60-75 days, and you'll learn the whole cycle in one season.
Plan with the seed spacing calculator, buy seeds from Johnny's or Baker Creek, and start. The hardest part is the first bed. The second is easy.
Related reading: the complete seed spacing guide and the FAQ.