How many hedge plants you need, and how far apart to plant them

How to work out the number of hedge plants

For a single row, the plants are the hedge length divided by the spacing, rounded up, plus one. The extra plant is the first one: ten gaps have eleven plants, like the posts of a fence. Mein schöner Garten puts it in plants per running metre: at 4 plants per metre the first metre takes 5 and every metre after it takes 4.

When the division is not exact, the calculator rounds the gaps up and spreads the plants evenly, a little closer than the spacing you chose. On 25 ft with plants 3 ft apart, 25 ÷ 3 = 8.33, so the hedge gets 9 gaps of 2' 9 1/4" and 10 plants.

In a staggered double row the first row stays the same and the second row has one plant in the middle of each gap, so one plant fewer than the first. The RHS suggests a double row for hedges thicker than 3 ft (90 cm), with the two rows 18 in (45 cm) apart. The distance between rows is in the advanced options.

Worked example: 30 feet of arborvitae

In US units the calculator opens with the most common American privacy hedge: 30 ft of arborvitae, 4 ft tall plants, 3 ft apart. Oregon State University Extension spaces arborvitae 3 to 4 feet apart.

• Gaps: 30 ÷ 3 = 10, an exact division
• Plants: 10 + 1 = 11 arborvitae
• In a staggered double row: 11 in the first row and 10 in the second, 21 plants

With landscape fabric you need one strip as long as the hedge: 30 ft, one 3 × 50 ft roll.

With cherry laurel 18 in apart, the same 30 ft (360 in) take 360 ÷ 18 = 20 gaps and 21 plants, or 41 in a staggered double row.

In the UK, with metres: 10 m of cherry laurel at 40 cm, the spacing OBI gives for 'Caucasica' plants 60 to 100 cm tall, is 10 ÷ 0.40 = 25 gaps and 26 plants, or 51 in a staggered double row.

How many hedge plants per foot: table by length

Single row, the same spacing along the whole hedge. 3 ft is the arborvitae spacing, 18 in privet (University of Minnesota, 'Cheyenne' privet), 12 in Korean boxwood.

Hedge length	3 ft apart	18 in apart	12 in apart
20 ft	8	15	21
30 ft	11	21	31
50 ft	18	35	51
100 ft	35	68	101

In metres, single row at 40 cm (cherry laurel, photinia, thuja): 14 plants for 5 m, 26 for 10 m, 51 for 20 m and 126 for 50 m. At 30 cm (privet, beech) the same lengths take 18, 35, 68 and 168.

Plant size and spacing when you buy

The bigger the plant, the wider you can space it. OBI gives spacing by height at purchase:

• Cherry laurel 'Caucasica': 30 cm up to 60 cm tall, 40 cm from 60 to 100 cm, 50 cm from 100 to 120 cm.
• Thuja 'Smaragd' (Emerald Green arborvitae): 30 cm up to 80 cm, 40 cm from 80 to 140 cm, 50 cm from 140 to 160 cm.
• Privet: 30 cm for plants 60 to 120 cm tall, 50 cm from 120 to 200 cm.
• Photinia: 2 or 3 per metre, usually sold at 60 to 80 cm; hornbeam 3 to 5 per metre; beech 3 to 4 per metre at 80 to 100 cm; box about 10 per metre at 10 to 15 cm.

In the US, American extension services give: arborvitae 3 to 4 ft (Oregon State), privet 18 in and Korean boxwood 1 ft for a clipped hedge (University of Minnesota), common boxwood 24 to 36 in as a landscape spacing (UF/IFAS). For cherry laurel, photinia, hornbeam and beech the calculator starts inside the RHS range of 1 to 2 ft; change it to the spacing on the plant tag.

Each plant keeps its own spacing and height in the calculator. Lay the weed fabric before planting and cut a cross where each plant goes. Enter the width and length of the roll you find (the calculator starts at 3 × 50 ft, or 1 × 10 m in metric); for a double row the fabric has to be wider than the distance between the rows, or the receipt warns you.

Common mistakes

• Length divided by spacing, and nothing else. The first plant is always missing: 30 ft at 3 ft is 11 plants, not 10.
• Doubling the plants for a double row. The staggered second row has one plant fewer than the first: 21, not 22.
• Planting too close for an instant screen. UGA Extension warns that crowded plants soon shade each other and thin out, with more disease.
• Planting on the property line. UGA Extension advises setting the hedge back from the line far enough for its mature width, so it does not grow into the neighbor's yard.
• The same spacing for every plant size. A 4 ft arborvitae goes wider than a 2 ft one: check the size table.