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Best compost

By Adele Dyer

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.

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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 2020.

In this article: 

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?.

Best compost for sowing seeds 

Brand Price Basil Petunia Score
Aldi Multipurpose Compost NS
Bathgate Champions Blend All Purpose £6.50 for 50 litres
Bord na Mona Growise Pro 5 All Purpose Compost £6.99 for 50 litres
Clover Multipurpose Compost £4.99 for 60 litres
Humax Original Compost £6.50 for 60 litres
Levington Multipurpose with Added John Innes £5.99 for 40 litres
Levington Seed & Cutting Compost £4.29 for 20 litres
Melcourt SylvaGrow Multipurpse Compost £7.49 for 50 litres
Melcourt SylvaGrow with added John Innes £8.49 for 50 litres
Sainsbury's Peat Free Compost £2 for 20 litres
Thompson & Morgan Incredicompost £14.99 for 75 litres
Verve Multipurpose compost £4.60 for 50 litres
Wilko Sowing & Cutting Compost £2 for 20 litres
Table notes
The more stars the better. Best Buys need to score more than 85%, Don’t Buys are 45% or less. Price based on 2019 selling price of a large bag. Smaller bags of many composts available, but are usually more expensive per litre. n/s = not stated. Aldi did not confirm final prices for this year as we went to press. Score ignores price and based on an equal weighting for basil and petunia. Germination 50%; size 20%; leaf colour 20%; health 10%.

Key

Member Content

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

Best compost for raising young plants 

Brand Price Cabbage Antirrhinum Score
Aldi Multipurpose Compost NS
Bathgate Champion's Blend All Purpose Compost £6.50 for 50 litres
Bord na Mona Growise Pro 5 All Purpose £6.99 for 50 litres
Clover Multi-Purpose Compost £4.99 for 60 litres
Levington Multipurpose with Added John Innes £5.99 for 40 litres
Levington Original Multipurpose Compost £7.49 for 70 litres
Melcourt SylvaGrow Multipurpose Compost £7.49 for 50 litres
Melcourt SylvaGrow with added John Innes £8.49 for 50 litres
Miracle-Gro Peat Free All Purpose Enriched Compost £5.99 for 50 litres
Thompson & Morgan Incredicompost £14.99 for 75 litres
Verve Multipurpose Compost £4.60 for 50 litres
Wilko Sowing & Cutting Compost £2 for 20 litres

Table notes
The more stars the better. Best Buys need to score more than 85%. Price is based on the 2019 cost of a large bag. Smaller bags of many composts are available, but are usually more expensive per litre. n/s = not stated. Aldi did not confirm final prices for this year. Score ignores price and is based on an equal weighting for cabbage and antirrhinum plants. Cabbage: size and weight 80%; foliage colour 10%; health 10%. Antirrhinum: size and weight 60%; flowering 20%; foliage colour and health 20%

Key

Member Content

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

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%.

Key

Member Content

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

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 22 different composts to grow basil 'Puck' and Petunia 'Express Rose' seeds. 
  • Raising young plants - we use 25 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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