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4 February 2021

Best compost

Are you looking for the best compost for your garden? We reveal the the top composts for sowing seeds, raising young plants and growing plants in containers.
All compost test results 2017
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Adele Dyer

The best compost will provide all the nutrients and support needed for seeds and veg to grow and thrive, while the worst will leave you with discoloured crops and pest-ridden plants.

But the only way to know if a compost is good or bad is to grow plants in it and compare them - something we've been doing for more than 30 years.

Last year alone, we completed over 70 different compost tests, growing various seeds, young plants, herbs and vegetables in temperature and humidity controlled greenhouses to bring you this comprehensive list of the best - and the worst - composts to buy in 2021.

Only logged-in Which? members can view our recommendations in the table below. If you're not yet a member, you can get instant access by joining Which?.

Compost for containers results will be updated in March 2021

Best compost for sowing seeds

Brand Price Basil Petunia Score
Champions Blend All Purpose Compost

£6.50 for 50 litres

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Clover Multi-Purpose Compost

£5.50 for 60 litres
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Homebase Multi-Purpose Compost

£4.95 for 50 litres
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Homebase Peat Free Multi-Purpose Compost

£4.95 for 50 litres
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Levington John Innes Seed Compost

£4.99 for 30 litres
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Levington Seed & Cutting Compost

£3.99 for 20 litres
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Melcourt Sylvagrow Multi-purpose

£7.99 for 50 litres
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Melcourt SylvaGrow with added John Innes

£8.99 for 50 litres
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The Greener Gardening Company Happy Compost all Purpose

£6.99 for 50 litres
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Thompson & Morgan Incredicompost

£14.99 for 70 litres
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Thompson & Morgan Incredipeatfree

£14.99 for 70 litres
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Westland John Innes Seed Sowing Compost

£6.99 for 35 litres
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Westland Multi Purpose Compost with John Innes

£5.99 for 50 litres
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Westland New Horizon All-Plant Compost

£6.99 for 50 litres
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Wilko Indoor/Outdoor Compost

£1.50 for 8 litres
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Wilko Multipurpose Compost

£3 for 50 litres
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Wilko Sowing & Cutting

£2 for 20 litres
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Table notes

USING THE TABLE The more stars the better. Best Buys highlighted in red, Don’t Buys highlighted in blue. Best Buys need to score more than 80%, Don’t Buys are 45% or less. PRICE. Based on the cost of a large bag. Smaller bags of many composts are available, but are usually more expensive per litre. n/s = not stated. GREEN COMPOST is composted green waste collected by local councils. SCORE ignores price and is based on an equal weighting for basil and petunia. Germination 50%, health 25%, size 20%, leaf colour 5%. 

For more information, head straight to our guide on the best composts for sowing seeds

Best compost for raising young plants

Brand Price Antirrhinum Tomato Score
Champions Blend All Purpose Compost

£6.50 for 50 litres

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Homebase Multi-Purpose Compost

£4.95 for 50 litres

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Homebase Peat Free Multi-Purpose Compost

£4.95 for 50 litres

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Levington John Innes No.1

£4.99 for 30 litres

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Levington Seed & Cutting

£3.99 for 20 litres

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Melcourt SylvaGrow Multi-purpose Compost

£7.99 for 50 litres

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Melcourt SylvaGrow with added John Innes

£8.99 for 50 litres
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The Greener Gardening Company Happy Compost All Purpose

£6.99 for 50 litres

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Thompson & Morgan Incredicompost

£14.99 for 70 litres

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Thompson & Morgan Incredipeatfree

£14.99 for 70 litres
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Westland John Innes No 1 Young Plant Compost

£6.99 for 35 litres

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Westland Multi-Purpose Compost with John Innes

£5.99 for 50 litres

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Westland New Horizon All Plant Compost

£6.99 for 50 litres

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Wilko Indoor/Outdoor Potting Compost

£1.50 for 8 litres

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Wilko Multipurpose Compost

£3 for 50 litres

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Table notes

USING THE TABLE The more stars the better. Best Buys highlighted in red, Don’t Buys highlighted in blue. Best Buys need to score more than 80%, Don’t Buys are 45% or less. PRICE. Based on the cost of a large bag. Smaller bags of many composts are available, but are usually more expensive per litre. n/s = not stated. GREEN COMPOST is composted green waste collected by local councils. SCORE ignores price and is based on an equal weighting for tomatoes and antirrhinums. Tomatoes: plant weight 50%, height 20%, health 20%, roots 10%. Antirrhinum: Flower number 30%, plant weight 30%, health 20%, height 10%, root growth 10%. 

For more information, head straight to our guide on compost for raising young plants

Best compost for containers

Brand Price Pelargonium Potatoes Score
Bathgate Champions Blend All Purpose Compost £6.50 for 50L
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Bord Na Mona Growise Pro 5 All Purpose £6.99 for 50L
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Clover Multi-Purpose £4.99 for 60L
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Dalefoot Wool Compost for Potting £12.99 for 30L
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Levington Multipurpose with John Innes £5.99 for 40L
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Marshalls Grower's Blend £13.98 for 2x 50L
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Melcourt SylvaGrow Sustainable Growing Medium £7.49 for 50L
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Miracle-Gro Peat Free All Purpose Enriched Compost £5.99 for 50L
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Sainsbury's Peat Free Multi-Purpose Compost £2 for 20L
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Thompson & Morgan Incredicompost £14.99 for 75L
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Verve Multipurpse Compost £4.60 for 50L
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Wilko Indoor & Outdoor Potting Compost £1.50 for 8L
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Table notes

Best Buys need to score 80% or more for peat-based composts and 71% or more for peat-free composts. Price: based on the cost of a 50L bag or the nearest equivalent. Smaller bags of compost are usually more expensive per litre. Score: ignores price and is based on an equal weighting for pelargoniums and potatoes. Pelargoniums: number of flowers 33.3%, size 33.3%, foliage colour 33.3%. Potatoes: yield 75%, quality 25%.

For more information, head straight to our guide on compost for containers

Getting the best from compost

It’s best to buy only the amount of compost you need, and use it up as soon as possible. This is particularly true of peat, which ideally should be used sparingly as it's bad for the environment. If you need to store any compost for more than a month, put it in the shed where it will be cool and dry, or undercover, especially through wet weather. If you can’t use up peat-free compost within three months of buying it, use it as a mulch on your borders.

Why Which? compost reviews are better

Which? is independent and doesn't accept advertising or freebies, so you can trust our reviews to give you the full, honest and impartial truth about a product.

We test compost for three different tasks; sowing seeds, raising young plants and for use in containers. 

  • Sowing seeds - we use 17 different composts to grow basil 'Cinnamon' and Petunia 'Express Rose' seeds. 
  • Raising young plants - we use 15 different composts to grow cabbage and antirrhinum bought as plug plants from a specialist nursery. 
  • Containers - we use 25 different composts to grow pelargoniums and potatoes. 

All three tests are carried out by an expert at a horticultural institute in a temperature and humidity-controlled greenhouse and the results are compiled by an independent assessor who's an expert in compost and plant health. 

We also send secret shoppers to buy our composts, so we can be sure we're getting the same compost as you. 

Find out more in our guide on how we test compost. Alternatively, jump straight to our round-up of the best controlled release fertilisers

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