How Many Ground Cover Plants Do I Need

How many ground cover plants do I need for a bed of known size? Start with the area, then the spacing, then the layout, then the plants per flat, then the extra percentage for losses. The Ground Cover Calculator turns those five inputs into a plant count and a flat count, so you can order with a number in hand instead of a guess.

What a preset does and what it does not do

A preset sets the spacing only, not the area, layout, plants per flat, or extra percentage.

The calculator preset list has 8 ground covers. Creeping thyme uses 30 cm, which is 12 in. Pachysandra uses 20 cm, which is 8 in. Vinca periwinkle uses 40 cm, which is 15 in. Ajuga uses 30 cm, which is 12 in. Liriope uses 30 cm, which is 12 in. Creeping phlox uses 45 cm, which is 18 in. Sedum uses 30 cm, which is 12 in. Clover lawn plugs use 15 cm, which is 6 in. A preset never gives a different count than the same spacing entered by hand.

The page formula step by step

Plants per square metre equals 1 divided by spacing squared, with spacing in metres, in a square grid. Plants per square foot equals 144 divided by spacing squared, with spacing in inches. In a triangular layout, divide the square grid figure by 0.8660254.

Plants equals area times plants per unit area times 1 plus the extra percentage, rounded up to a whole plant, because you cannot buy part of a plant. Flats equals plants divided by plants per flat, rounded up in the same way.

Doubling the area doubles the plant count before the round up step. On 25 m² at 30 cm, with 5% extra, the count is 292 plants, and on 50 m² it is 584 plants, which is twice 292. The Ground Cover Calculator shows the plant count and the flat count together.

Worked example 1: metric, 10 m² at 30 cm

The page metric example covers 10 m² with plants 30 cm apart in a square grid, with 5% extra. Spacing in metres is 0.3, so plants per square metre equals 1 divided by 0.09, which is 11.11. Plants equals 10 times 11.11 times 1.05, which is 116.667, rounded up to 117. Flats equals 117 divided by 18, which is 6.5, rounded up to 7. So the order is 117 plants and 7 flats of 18.

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

The page imperial example covers 100 sq ft at 12 in spacing in a square grid, with 5% extra. Plants per square foot equals 144 divided by 144, which is 1. Plants equals 100 times 1 times 1.05, which is 105. Flats equals 105 divided by 18, which is 5.833, rounded up to 6. So the order is 105 plants and 6 flats of 18.

Keep the two examples separate. The defaults are rounded equivalents, not exact conversions. An area of 10 m² is 107.64 sq ft, not 100 sq ft, and 100 sq ft is 9.29 m², not 10 m². Spacing of 30 cm is 11.81 in, not 12 in, and 12 in is 30.48 cm, not 30 cm.

The spacing band and how fast cover arrives

Ground cover is usually planted 15 to 45 cm apart, which is 6 to 18 in, depending on the plant and how fast you want cover. Closer spacing gives faster cover at higher cost. Wider spacing gives slower cover at lower cost.

At 12 in spacing, the density is 1 plant per square foot. At 6 in, it is 4 plants per square foot. At 18 in, it is about 0.44 plants per square foot. Halving the spacing from 12 in to 6 in gives four times as many plants, not twice as many, because spacing enters the formula squared. Ground cover typically takes one to three growing seasons to fill in. The spread rate varies with soil, light and variety. Remove perennial weeds before planting.

All 8 presets at 10 m²

The table below uses a square grid, 5% extra, and flats of 18, on an area of 10 m².

Preset	Spacing	Plants	Flats of 18
Creeping thyme	30 cm	117	7
Pachysandra	20 cm	263	15
Vinca periwinkle	40 cm	66	4
Ajuga	30 cm	117	7
Liriope	30 cm	117	7
Creeping phlox	45 cm	52	3
Sedum	30 cm	117	7
Clover lawn plugs	15 cm	467	26

Clover lawn plugs need the most plants, 467, at 15 cm, the closest spacing. Creeping phlox needs the fewest, 52, at 45 cm, the widest spacing. Pachysandra needs 263 plants, more than twice the 117 for creeping thyme. Creeping thyme, ajuga, liriope and sedum share the same count at 30 cm.

All 8 presets at 100 sq ft

The table below uses a square grid, 5% extra, and flats of 18, on an area of 100 sq ft. Keep this table separate from the metric table above, because the areas and the spacings are rounded equivalents, not exact conversions.

Preset	Spacing	Plants	Flats of 18
Creeping thyme	12 in	105	6
Pachysandra	8 in	237	14
Vinca periwinkle	15 in	68	4
Ajuga	12 in	105	6
Liriope	12 in	105	6
Creeping phlox	18 in	47	3
Sedum	12 in	105	6
Clover lawn plugs	6 in	420	24

Clover lawn plugs need the most plants, 420, and creeping phlox needs the fewest, 47. Pachysandra needs 237 plants, more than twice the 105 for creeping thyme. Creeping thyme, ajuga, liriope and sedum again share one count at 12 in.

Flats of 18, 32 and 36 for the same plant count

Flats are commonly 18, 32 or 36 plants, depending on cell size, so check with your nursery. The plants per flat default is 18, with limits of 1 to 200. Enter 1 for individual pots.

For the page metric example, 117 plants is 4 flats of 32 and 4 flats of 36, because 117 divided by 32 is 3.656, rounded up to 4, and 117 divided by 36 is 3.25, rounded up to 4. For the page imperial example, 105 plants is 4 flats of 32 and 3 flats of 36, because 105 divided by 32 is 3.28, rounded up to 4, and 105 divided by 36 is 2.916, rounded up to 3.

Defaults, limits and the extra percentage

The area default is 10 m², which is 100 sq ft, with limits of 0.1 to 1,000,000. The spacing default is 30 cm, which is 12 in, with limits of 2 to 300. The layout default is square, with triangular as the staggered choice. The plants per flat default is 18, with limits of 1 to 200. The extra default is 5%, with a range of 0 to 50% and a step of 0.1%.

The extra percentage covers plants that fail. On 10 m² at 30 cm, 0% extra gives 112 plants, 5% gives 117, 10% gives 123, and 20% gives 134. A higher extra percentage does not always mean more flats: 112, 117 and 123 plants all need 7 flats of 18, while 134 plants need 8 flats of 18.

Square grid and staggered layout

A staggered layout, also called triangular, needs about 15% more plants than a square grid at the same spacing. The exact uplift from the 0.8660254 factor is 15.47%, because 1 divided by 0.8660254 is 1.1547.

On 10 m² at 30 cm, with 5% extra, a square grid needs 117 plants and a triangular layout needs 135 plants, which is 18 more plants and 15.4% more, with flats rising from 7 to 8. On 100 sq ft at 12 in, a square grid needs 105 plants and a triangular layout needs 122 plants, which is 17 more plants, with flats rising from 6 to 7. Choose the layout before you order.

How to use the calculator

Measure the area to plant, choose a preset 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. The calculator gives mulch at 5 cm deep, shown as 2 in in imperial. Use the same unit system through the whole calculation.

The page assumptions in one place

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. Those four points are the page assumptions.

The Plant Spacing Calculator, the Plants per Square Foot Calculator, the Garden Area Calculator, and the Plants per Acre Calculator cover the related steps.

Frequently asked questions

Q: How many ground cover plants do I need for 10 m² at 30 cm spacing?
A: 117 plants, including 5% extra, in a square grid, which is 7 flats of 18.

Q: How many ground cover plants do I need for 100 sq ft at 12 in spacing?
A: 105 plants, including 5% extra, in a square grid, which is 6 flats of 18.

Q: What spacing should ground cover plants have?
A: Usually 15 to 45 cm, which is 6 to 18 in, depending on the plant and how fast you want cover.

Q: Does a preset change the area or the number of plants per flat?
A: No, a preset sets the spacing only, not the area, the layout, the plants per flat or the extra percentage.

Q: How many plants are in a flat of ground cover?
A: Commonly 18, 32 or 36 depending on cell size, so check with your nursery.

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