How the grid works
According to Phipps Conservatory's guide, the method was developed in the late 1970s by Mel Bartholomew to grow "more food in less space", planting in square blocks rather than rows. UF/IFAS Gardening Solutions describes the standard bed as a 4 × 4 ft planting area divided into sixteen 1 × 1 ft squares, with aisles about three feet wide; a 3 × 3 ft bed gives nine squares, and rectangles work too. To mark the grid, Phipps suggests noting every foot along the four sides of the bed and connecting the marks with string, sticks, old blinds or lines drawn in the soil.
- 1 per square: tomato, pepper, broccoli, cabbage
- 4 per square: lettuce, chard (UF), parsley
- 9 per square: beets (UF), bush beans, spinach (NCSU)
- 16 per square: carrots, radishes, onions (UF)
- Plants per square = (12 ÷ spacing in inches)²
The spacing math
plants per square foot = (12 ÷ spacing in inches)²
12-inch spacing → 1 · 6-inch → 4 · 4-inch → 9 · 3-inch → 16
NC State's chart pairs each count with exactly these spacings (16 at 3 inches, 9 at 4 inches, 4 at 6 inches, 1 at 12 inches). Its 2-per-square tier uses 8-inch spacing, and its trellised tier puts 8 peas or pole beans along one side of a square at 3-inch spacing.
Plants per square foot, three charts compared
| Crop | UF/IFAS | NC State | Phipps |
|---|---|---|---|
| Tomato | 1 | 1 | 1 per 2 × 2 ft block |
| Pepper | 1 | 1 | 1 |
| Eggplant | 1 | 1 | 1 |
| Broccoli | 1 | 1 | 1 |
| Cabbage | 1 | 1 | 1 |
| Cauliflower | — | 1 | — |
| Kale | 1 | 2 | 1 |
| Collards | 1 | — | 1 |
| Okra | 1 | 1 | 1 |
| Potato | 1 | 1 | — |
| Sweet potato | 1 | 2 | 1 |
| Cucumber (trellised) | 2 | 2 | 2 |
| Summer squash, zucchini | — | 1 per 2 sq ft | 1 per 3 × 3 ft block |
| Winter squash, melons | — | 1 per 2 sq ft | 1 per 2 sq ft |
| Lettuce (heads) | 4 | 4 | 4 |
| Swiss chard | 4 | 4 | 2 |
| Spinach | 4 | 9 | 9 |
| Bok choy | 4 | — | — |
| Mustard greens | — | — | 9 |
| Parsley | 4 ("many herbs") | 4 | 2 |
| Basil | 4 ("many herbs") | — | 2 |
| Cilantro | — | — | 9 |
| Dill | — | — | 4 |
| Oregano | — | — | 2 |
| Corn | — | 4 | — |
| Beets | 9 | 9 | 16 |
| Turnips | 9 | 9 | — |
| Bush / snap beans | 9 (string beans) | 9 | 9 |
| Peas (trellised) | 9 | 8 | 8 |
| Pole beans (trellised) | — | 8 | 8 |
| Onions (bulbing) | 16 | 9 | 9 |
| Garlic | — | 9 | 16 |
| Green onions / scallions | — | 16 | 4 bunches |
| Carrots | 16 | 16 | 16 |
| Radishes | 16 | 16 | 16 |
Where charts disagree (beets 9 or 16, onions 9 or 16, spinach 4 or 9), the lower number gives each plant more room; the higher one assumes smaller harvests such as baby beets. Note that NC State's PDF contains two charts and the first is garbled; the figures above come from its second, cleaner chart.
Soil, size and trellises
UF/IFAS suggests filling the box completely with blended compost, or using equal parts coarse vermiculite, peat moss and blended compost. Bed dimensions follow general raised-bed advice: the University of Delaware recommends 4-foot widths so the center is reachable and at least 12 inches of depth. Put trellised crops on the north side so they do not shade the rest; Virginia Cooperative Extension recommends placing small sun-loving crops on the south side of taller ones, and driving trellis posts at least 18 to 24 inches into the ground.
A 4 × 4 ft bed at 12 inches deep needs 16 cubic feet of mix; check other sizes with the soil calculator.
Sources
- UF/IFAS Gardening Solutions — Square Foot Gardening
- NC State Plants for Human Health Institute — Square Foot Seeds (PDF)
- Phipps Conservatory and Botanical Gardens — Square Foot Gardening Guide (PDF, 2020)
- University of Delaware Cooperative Extension — Raised Bed Gardening (PDF)
- Virginia Cooperative Extension — Vertical Gardening Using Trellises, Stakes, and Cages (HORT-189NP)
All sources were opened and checked in October 2026. Rules and figures change; confirm with the original before acting.