Offset rows fit about 15% more in
Most people plant on a square grid because it is the obvious thing to do and it makes hoeing easy. But a square grid is not the densest way to pack circles into a rectangle, and plants are effectively circles.
In an offset or triangular layout, each row is shifted half a spacing sideways and the rows sit closer together — by a factor of √3/2, about 0.866 — while every plant stays exactly the same distance from all of its neighbours. The plants are no more crowded than in a square grid; there is simply less wasted space between the rows. On a bed deep enough for the tighter gap to buy an extra row, the gain is around 15%. On a narrow bed it can be nothing at all, or slightly negative — which is why the calculator shows both totals rather than assuming the gain.
The trade-off is access. A square grid leaves straight clear lines in both directions, which means you can run a hoe through it. An offset bed has no straight line anywhere and has to be weeded by hand. For a small intensively worked bed that is fine. For a long row you intend to hoe, it is not worth it.
Spacing is about light and air, not roots
The usual explanation for plant spacing is competition for nutrients and water. That is real but secondary, and it is fixable — you can feed and water more. What you cannot fix is light and airflow.
A plant that is shaded by its neighbours for the second half of the season produces less regardless of how well fed it is, and it produces later. This is why the recommended spacing for a crop grown for its fruit is usually wider than for the same plant grown for leaves: a lettuce only has to make leaves, a tomato has to ripen fruit, and ripening needs light.
Airflow is the other half, and it is a disease question. Blight, mildew and botrytis all need leaf surfaces to stay wet. Plants packed close enough that the foliage never dries out after rain are dramatically more likely to be hit. In a wet climate, spacing tomatoes and courgettes generously is a disease-control measure, not a luxury.
The honest caveat: published spacings assume good conditions. In a hot dry climate closer spacing shades the soil and reduces evaporation, which helps. In a cool damp one, the same spacing invites mildew. Adjust toward the wider figure if your summers are wet.
| Crop | In row | Between rows | Per m² |
|---|---|---|---|
| Radish | 4 cm | 15 cm | 166 |
| Carrot | 5 cm | 30 cm | 66 |
| Lettuce | 25 cm | 30 cm | 13 |
| Tomato | 45 cm | 75 cm | 3 |
| Kale | 45 cm | 60 cm | 3.7 |
| Courgette | 90 cm | 90 cm | 1.2 |
| Winter squash | 120 cm | 150 cm | 0.55 |
Raise more than you need
The plant count this calculator gives you is how many will fit the bed. It is not how many seeds to sow, and treating it as such is why people end up with gaps.
Germination is never total, some seedlings are weak and get culled, slugs take a share in the first fortnight, and one or two will simply fail after planting out for no visible reason. Raising 20% more than the bed needs costs almost nothing when you are sowing your own and removes all of that risk.
The seed starting calculator does this arithmetic properly, allowing for germination rate and culling. If you are buying plug plants rather than raising your own, the same logic applies with a smaller margin — plugs arrive established, so 10% spare is usually enough.
Common questions
How many tomato plants fit in a 4 × 8 ft bed?
At 45 cm in the row and 75 cm between rows it takes 12 on a square grid — two rows of six. An offset layout gives 11 here, because the closer row gap does not buy a third row while the alternate row still loses a plant.
Is offset planting worth it?
On a large bed it fits about 15% more plants in at the same neighbour distance. On a narrow bed it can fit fewer, because the tighter row gap may not buy an extra row while alternate rows still lose a plant each. The calculator shows both totals so you can see which applies.
Can I plant closer than the recommended spacing?
For leaf crops, often yes. For anything grown for fruit, closer spacing reduces light and airflow, which means later ripening and much more disease in a damp climate.