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12 July 2021

Best compost to buy in 2021

Discover the top-scoring composts for sowing seeds, raising young plants and growing plants in containers.
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Adele Dyer
All compost test results 2017

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 meagre crops and feeble 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.

Many people no longer want to buy peat compost as it's believed to damage the environment and add considerably to global warming. However, peat composts are still the most widely-available composts in garden centres and are preferred by many gardeners. 

Find out more about peat vs peat-free compost and make up your own mind about where you stand. 

To make it easier to choose the right compost for you, we have separated our results in two sections. The first lists the peat-free composts we have tested, and you can find our recommendations for peat composts at the bottom of the page.

Keep scrolling for our comprehensive list of the best - and the worst - composts to buy in 2021. 

Not sure what compost you need? See our guide on how to choose the right compost

Best peat-free compost for sowing seeds

Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.

Peat-free compost
Price
Basil
Petunia
Score
Homebase Peat Free Multi-Purpose Compost
£4.95 for 50 litres
Melcourt Sylvagrow Multi-purpose
£7.99 for 50 litres
Melcourt SylvaGrow with added John Innes
£8.99 for 50 litres
The Greener Gardening Company Happy Compost all Purpose
£6.99 for 50 litres
Thompson & Morgan Incredipeatfree
£14.99 for 70 litres
Westland New Horizon All-Plant Compost
£6.99 for 50 litres
Table notes: Peat-free compost Best Buy needs to score more than 65% Don’t Buys are less than 45%.
PRICE Based on the cost of a large bag. Smaller bags of many composts are available, but are usually more expensive per litre.
SCORE ignores price and is based on an equal weighting for basil and petunia. Germination 50%, health 25%, size 20%, leaf colour 5%. 

Best peat-free compost for raising young plants

Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.

Peat-free compost
Price
Antirrhinum
Tomato
Score
Homebase Peat Free Multi-Purpose Compost
£4.95 for 50 litres
Melcourt SylvaGrow Multi-purpose Compost
£7.99 for 50 litres
Melcourt SylvaGrow with added John Innes
£8.99 for 50 litres
The Greener Gardening Company Happy Compost All Purpose
£6.99 for 50 litres
Thompson & Morgan Incredipeatfree
£14.99 for 70 litres
Westland New Horizon All Plant Compost
£6.99 for 50 litres
Table notes: 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.
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%.

Best peat-free compost for containers

Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.

Peat-free compost
Price
Pelargonium
Potatoes
Score
Homebase Peat Free Multi-purpose Compost
£5.25 for 50L
Melcourt SylvaGrow Multi-purpose
£7.99 for 50L
Melcourt SylvaGrow with added John Innes
£8.99 for 50L
Melcourt SylvaGrow Tub & Basket
£8.99 for 50L
Miracle-Gro Premium Peat Free All Purpose
£5.99 for 40L
The Greener Gardening Co Happy Compost All Purpose
£4.60 for 50L
Thompson & Morgan Incredipeatfree
£14.99 for 70L
Westland New Horizon All Plant Compost
£6.99 for 50L
Table notes: Best Buys need to score 70% or more for peat-free composts.
PRICE Based on the cost of a large bag. 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: overall score for pots where we added fertiliser 20%; number of flowers 16%; flowering impact 16%; size 16%; foliage colour 16%; vigour 16%. Potatoes: yield 50%; tuber size 50% (the percentage of potatoes that are large enough to be quickly prepared for cooking).

We also test grow bags - see our round-up of the best grow bags.

Best peat composts for sowing seeds

Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.

Peat compost
Price
Basil
Petunia
Score
Champions Blend All Purpose Compost
£6.50 for 50 litres
Clover Multi-Purpose Compost
£5.50 for 60 litres
Homebase Multi-Purpose Compost
£4.95 for 50 litres
Levington John Innes Seed Compost
£4.99 for 30 litres
Levington Seed & Cutting Compost
£3.99 for 20 litres
Melcourt SylvaGrow with added John Innes
£8.99 for 50 litres
Thompson & Morgan Incredicompost
£14.99 for 70 litres
Westland John Innes Seed Sowing Compost
£6.99 for 35 litres
Westland Multi Purpose Compost with John Innes
£5.99 for 50 litres
Wilko Indoor/Outdoor Compost
£1.50 for 8 litres
Wilko Multipurpose Compost
£3 for 50 litres
Wilko Sowing & Cutting
£2 for 20 litres

Best peat composts for raising young plants

Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.

Peat compost
Price
Antirrhinum
Tomato
Score
Champions Blend All Purpose Compost
£6.50 for 50 litres
Homebase Multi-Purpose Compost
£4.95 for 50 litres
Levington John Innes No.1
£4.99 for 30 litres
Levington Seed & Cutting
£3.99 for 20 litres
Thompson & Morgan Incredicompost
£14.99 for 70 litres
Westland John Innes No 1 Young Plant Compost
£6.99 for 35 litres
Westland Multi-Purpose Compost with John Innes
£5.99 for 50 litres
Wilko Indoor/Outdoor Potting Compost
£1.50 for 8 litres
Wilko Multipurpose Compost
£3 for 50 litres

Best peat composts for containers

Only logged-in Which? members can view our recommendations in the table below. Join Which? to get instant access.

Peat compost
Price
Pelargonium
Potatoes
Score
Bathgate Champions Blend All Purpose Compost
£6.50 for 50L
Homebase Multi-purpose Compost
£5.25 for 50L
Levington Multi Purpose Compost with added John Innes
£4.99 for 40L
Miracle-Gro Premium All Purpose Compost for All Plants
£6.99 for 50L
Thompson & Morgan Incredicompost
£14.99 for 70L
Westland Multi-purpose Compost with added John Innes
£6.99 for 60L

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. 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. Peat ideally should be used sparingly as it's bad for the environment. 

Find out more about why you should buy peat-free compost.

Why Which? compost reviews are better

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 tomato and antirrhinum, sown as seed and transplanted when they have two non-seed leaves. 
  • Containers - we use 25 different composts to grow pelargoniums and potatoes. 

All three tests are carried out by an expert at a horticultural institute, and the compost for seeds and young plants test takes place in a temperature and humidity-controlled greenhouse. The composts for containers are tested outside once the nights are frost-free. 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