Plant spacing and seed depth
Use this selected Colorado State University Extension reference to check plant positions and seed depth before calculating a layout. Dimensions are in inches. Follow the variety’s directions and local guidance when they differ; seed depth is not transplant depth.
| Crop | Final spacing | Seed depth |
|---|---|---|
| Beets | 4–6 in | 3/4–1 in |
| Broccoli | 18 in | 1/2 in |
| Cabbage | 18 in | 1/2 in |
| Carrots | 2–3 in | 1/4 in |
| Kohlrabi | 7–9 in | 1/2 in |
| Leeks | 4–6 in | 1/4 in |
| Leaf lettuce | 7–9 in | 1/4 in |
| Green onions | 2–3 in | 1/4 in |
| Parsnips | 5–6 in | 1/2 in |
| Radishes | 2–3 in | 1/2 in |
| Spinach | 4–6 in | 1/2 in |
| Swiss chard | 7–9 in | 1 in |
| Turnips | 4–6 in | 1/2 in |
| Snap beans | 6 in; alternate: 4 × 12 in | 1–1 1/2 in |
| Corn | 12 × 30 in or 9 × 36 in | 1–1 1/2 in |
| Cucumbers | 6 in trellised; 24–36 in untrellised | 1 in |
| Eggplant | 18–24 in | 1/4 in |
| Pepper | 15–18 in | 1/4 in |
| Tomato | 24 in, trellised | 1/4 in |
| Summer squash | 36–48 in | 1–1 1/2 in |
Distinguish final spacing from a planting schedule
CSU’s guide describes equal-distance spacing for block or close-row beds unless a paired arrangement is listed. The closer end of a range assumes improved soil with 4–5% organic matter. These are Colorado reference values, not a nationwide prescription for every variety or row system.
Treat the spacing column as final plant positions. For crops started indoors, the seed-depth column concerns sowing, not the depth at which to set a transplant. Support systems also matter: a trellised crop may use different spacing from an unsupported crop.
Check growing conditions separately
A spacing chart answers where plants fit. It does not decide when the soil is ready, whether frost risk has passed or whether a particular crop suits the site. Consult local Extension guidance and the seed packet for those decisions.
Keep sowing depth in inches when reading the chart. Convert the selected final spacing to feet before entering a calculator that asks for feet: 12 in equals 1 ft. Record plant-to-plant spacing and row-to-row spacing separately when the chosen layout uses different distances.
Count positions between the margins
Mark the bed boundaries and the required distance from each end to the first and last plant. Subtract both end margins from the row length. Divide the usable span by spacing, round down to a whole number of intervals and add one for the first plant.
The finite-row formula is floor((length − 2 × end margin) ÷ spacing) + 1. Length, margin and spacing must use the same unit; spacing must be positive, and the two margins cannot exceed the length. For a rectangular grid, calculate positions in each direction and multiply.
This counts planting positions, not guaranteed living plants. The seed-count calculator additionally uses a stated germination fraction and seeds per station. A germination adjustment estimates the number of seeds to obtain; it cannot guarantee establishment.
Worked example: count a row including both end positions
- Inputs
- A row is 12 ft long, each end margin is 0.5 ft, and the chosen plant spacing is 1 ft.
- Calculation
Usable span: 12 − 2 × 0.5 = 11 ft. Intervals: floor(11 ÷ 1) = 11. Positions: 11 + 1 = 12.- Result
- 12 planting positions
The centers run from 0.5 ft to 11.5 ft. The 1 ft spacing illustrates the counting method; use a suitable crop-specific spacing. Round down the intervals before adding the first position.
Conclusion
Select crop-appropriate spacing and depth, check local timing separately, and count positions within explicit margins. Keep final plant positions separate from the number of seeds needed for sowing.