How to calculate how many plants you need
Plant labels give a spacing, the distance from the center of one plant to the center of the next when both are fully grown. To turn that into a number of plants, you divide the area of the bed by the space each plant needs.
- Find the bed area. Length times width for a rectangle, or 3.14 times the radius squared for a round bed. A 10 by 4 foot bed is 40 square feet, or 5,760 square inches.
- Find the space per plant. In a square grid, each plant takes spacing times spacing. At 18 inches, that is 324 square inches.
- Divide. 5,760 divided by 324 is about 18 plants in a square grid.
- Staggered layout. Offsetting every other row packs plants more efficiently, so multiply the space per plant by 0.866. The same bed then holds about 21 plants.
Square grid or staggered rows?
A square grid is easy to lay out and works well for vegetables in rows and raised beds. A staggered, or triangular, layout places each plant in a zigzag so every plant is the same distance from its neighbors. It fits about 15 percent more plants, fills in faster and looks more natural, which is why designers use it for groundcovers and flower borders.
Common plant spacing guide
| Plant type | Typical spacing |
|---|---|
| Lettuce, radishes, herbs | 4 to 8 in (10 to 20 cm) |
| Groundcovers, strawberries | 10 to 12 in (25 to 30 cm) |
| Annual flowers | 12 to 15 in (30 to 38 cm) |
| Perennials | 18 to 24 in (45 to 60 cm) |
| Tomatoes, peppers, hostas, lavender | 18 to 24 in (45 to 60 cm) |
| Small shrubs | 3 to 4 ft (90 to 120 cm) |
Crowded plants compete for water and light and are more prone to disease, while plants spaced too far apart leave bare soil for weeds. Following the label and filling gaps with mulch in the first season gives the best of both. For planting ideas, see our small garden and backyard ideas and summer patio ideas, and work out the mulch with the mulch calculator.