Square vs Staggered Ground Cover Planting

Square vs staggered ground cover planting is a choice about layout, not about plant type. The same area and the same spacing give a different plant count in each layout, and the difference can change the number of flats you order.

What a square grid looks like

In a square grid the plants sit in straight rows and straight columns. The gaps between plants form squares, and the centre of each square stays open until the plants spread. That open centre can leave bare soil visible for longer, and it is also the reason the square count is the lower count.

What staggered rows look like

In staggered rows every other row is offset, so each plant sits in the gap of the row before it. The plants form triangles rather than squares, and the pattern is often called triangular planting. The offset closes the open centre that a square grid leaves, so the plants cover the soil more evenly. The trade off is that the same area needs more plants at the same spacing. The Ground Cover Calculator offers both layouts, with square as the default.

The geometry gives an exact uplift. The page uses a factor of 0.8660254, and 1 divided by 0.8660254 equals 1.1547. That means a staggered layout needs 15.47 percent more plants than a square grid at the same spacing, which the page states as about 15 percent more.

The page formula step by step

The calculator works from area, spacing, layout, plants per flat, and extra percentage. Plants per square metre in a square grid equals 1 divided by spacing squared, with spacing in metres. In a staggered layout it equals 1 divided by spacing squared times 0.8660254. Plants equals area times plants per square metre times 1 plus the extra percentage, rounded up to a whole plant. Flats equals plants divided by plants per flat, rounded up to a whole flat. The default plants per flat is 18, and the default extra percentage is 5 percent. Extra percentage can be set from 0 percent to 50 percent, and plants per flat from 1 to 200, with 1 for individual pots.

Worked example 1: metric, 10 m² at 30 cm

The page metric example is 10 m² at 30 cm spacing in a square grid, with 5 percent extra. Spacing of 0.3 m gives 11.11 plants per m², because 1 divided by 0.09 equals 11.11. Plants equals 10 times 11.11 times 1.05, which is 116.67, rounded up to 117 plants. Flats equals 117 divided by 18, which is 6.5, rounded up to 7 flats of 18.

The same area and spacing in a staggered layout gives 135 plants and 8 flats of 18. That is 18 more plants, which is 15.4 percent more, close to the exact uplift of 15.47 percent.

Worked example 2: imperial, 100 sq ft at 12 in

The page imperial example is 100 sq ft at 12 in spacing in a square grid, with 5 percent extra. Plants per sq ft equals 144 divided by 144, which is 1. Plants equals 100 times 1 times 1.05, which is 105 plants. Flats equals 105 divided by 18, which is 5.83, rounded up to 6 flats of 18.

The same area and spacing in a staggered layout gives 122 plants and 7 flats of 18. That is 17 more plants. The rounded up counts give 16.2 percent more, because the extra plants round up in both counts. Keep the two examples separate. They use rounded equivalents, not exact conversions, because 10 m² is 107.64 sq ft, not 100 sq ft, and 30 cm is 11.81 in, not 12 in.

Table 1: square vs staggered at 10 m²

The table below compares the two layouts at 10 m² with 5 percent extra and flats of 18, at five spacings from 15 cm to 45 cm.

Spacing	Square plants	Square flats of 18	Triangular plants	Triangular flats of 18
15 cm	467	26	539	30
20 cm	263	15	304	17
30 cm	117	7	135	8
40 cm	66	4	76	5
45 cm	52	3	60	4

The plant difference is 72 at 15 cm, 41 at 20 cm, 18 at 30 cm, 10 at 40 cm, and 8 at 45 cm. The staggered layout needs at least one more flat at every spacing shown. Spacing is the larger choice. Moving from 15 cm to 45 cm in a square grid cuts the count from 467 plants to 52 plants, while changing the layout changes the count by about 15 percent.

The extra percentage and the flat count

The extra percentage is an allowance for losses, and the calculator default is 5 percent. It changes the plant count, but it does not always change the flat count. Table 2 shows the effect on 10 m² at 30 cm in a square grid.

Extra	Plants	Flats of 18	Flats of 32	Flats of 36
0%	112	7	4	4
5%	117	7	4	4
10%	123	7	4	4
20%	134	8	5	4

Changing the extra percentage from 0 percent to 10 percent changes the plant count from 112 plants to 123 plants, but it does not change the flats of 18 count, because 112, 117, and 123 plants all need 7 flats of 18. A higher extra percentage does not always mean more flats. The flat count only changes when the plant count crosses a flat boundary, as at 20 percent extra, where 134 plants need 8 flats of 18 and 5 flats of 32.

Two warnings before you order

First, a table with no extra percentage understates the order. For example, 100 plants per 100 sq ft at 12 in square with no extra is the count before losses, against 105 plants with the calculator 5 percent default. State the extra percentage beside any count you quote.

Second, do not mix the layouts when you compare counts. A staggered count at one spacing is not a square count at a closer spacing, and a square count does not order a staggered bed. The Plants per Square Foot Calculator gives density per square foot, and the Plants per Acre Calculator gives density per acre, but neither gives flats or an extra percentage. The Plant Spacing Calculator covers a single spacing in a bed, and the Garden Area Calculator covers measuring the garden area.

Mulch while the plants fill in

The calculator shopping list gives mulch at 5 cm deep, shown as 2 in in imperial. Mulch volume equals area times 5 cm depth. For 10 m² the volume is 0.5 m³, and for 100 sq ft the volume is 16.4 cu ft. Mulch goes between plants until they spread. The mulch quantity does not change with the layout, because it depends on area and depth only.

The page assumptions

Spread rate varies with soil, light and variety. Closer spacing gives faster cover at higher cost. Remove perennial weeds before planting. Ground cover typically takes one to three growing seasons to fill in. Spacing is usually 15 to 45 cm, which is 6 to 18 in, depending on the plant and how fast you want cover. Plants per flat are commonly 18, 32 or 36 depending on cell size, so check with your nursery.

What the calculator does not give

The calculator gives plant counts, flats, densities, and a mulch volume at 5 cm depth only, from area, spacing, layout, plants per flat, and extra percentage. It gives no plant cost, seed count, yield figure, fertiliser rate, watering figure, soil volume, coverage time in days or weeks, recommended spacing beyond the preset spacing values, or mature spread figure. It also gives no ground cover versus lawn comparison. The comparison here is square versus staggered only.

How to use the calculator

Measure the area, choose a ground cover or enter its spacing, choose a square or staggered layout, enter plants per flat or 1 for individual pots, then mulch between plants until they spread. A preset sets the spacing only, so a preset gives the same plant count as the same spacing entered by hand. Choose the square grid for the lower plant count, and choose staggered rows for more even cover, accepting about 15 percent more plants.

Frequently asked questions

Q: How many more plants does a staggered layout need?
A: About 15 percent more than a square grid at the same spacing. The exact uplift is 15.47 percent.

Q: How many plants do I need for 10 m² at 30 cm?
A: 117 plants square and 135 plants staggered, both with 5 percent extra. That is 7 flats of 18 square and 8 flats of 18 staggered.

Q: How many plants do I need for 100 sq ft at 12 in?
A: 105 plants square and 122 plants staggered, both with 5 percent extra. That is 6 flats of 18 square and 7 flats of 18 staggered.

Q: Does a higher extra percentage always mean more flats?
A: No. On 10 m² at 30 cm square, 0 percent, 5 percent and 10 percent extra all need 7 flats of 18, while plants rise from 112 to 123.

Q: How much mulch do I need for 10 m²?
A: 0.5 m³ at 5 cm deep, and 16.4 cu ft for 100 sq ft at the same depth.

Q: How long does ground cover take to fill in?
A: Typically one to three growing seasons. Spread rate varies with soil, light and variety.