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Peat-free compost for patio pots: which one works best?
With over a decade of experience at Which?, Tom covers everything from tech advice to money-saving tips, and highlights the best deals during major sales events.
We all look forward to colourful pots of summer bedding plants and bountiful veg, and getting the right compost is as important as the varieties you grow.
Thanks to the latest expert tests carried out by the Which? Gardening team, you can avoid disappointment by choosing a high-scoring compost. Every year, we're astounded by the difference between the best and worst, which is why we continue to test them.
Below, we take a closer look at the results of our latest peat-free compost tests. If you're a Which? member, you'll see which peat-free composts we rate highly, plus the bags to avoid.
- Three shoppers bought compost from garden centres, DIY stores and online to capture batch variation. We purchased three sets of each compost to reveal inconsistencies between batches.
- We planted three pots of ‘Charlotte’ potatoes and four pots of geranium ‘Horizon Violet’ from each of our three compost batches. The potatoes were planted in late April and the geraniums in early June.
- Our experts mixed a Best Buy controlled-release feed (CRF) into the pots of potatoes, as these hungry plants don’t grow well without plenty of nutrients. We grew a single seed potato in each 10L pot. For the geraniums, we mixed the same CRF into one pot from each batch and left the other three unfed to see their true quality.
- We assessed the potato foliage every two weeks and harvested the crop after 19 weeks. The potatoes from each pot were graded by size before being weighed and counted. We noted any issues with skin quality or rotting tubers. We assessed the geraniums every two weeks, scoring them for size, flowering, leaf colour and health.
The best peat-free composts
Which? test results revealed several Best Buy composts, and plants grown in them all excelled. The top-scoring pick is also a Best Buy for sowing seeds and raising young plants.
Log in now or join Which? to unlock our full table below.
| Peat-free compost | Which? test score | Our verdict |
|---|---|---|
Sign up to reveal Get instant access to this and all our scores and recommendations Unlock tableDigital first month £5, then £8.99 per month, cancel at any time. Already a member? | 94% (Best Buy) | An unbeatable choice to take your plants from a packet of seeds to mature plants. |
| 91% (Best Buy) | The geraniums all grew to an impressive size and flowered well. The potato harvest was very good, with plenty of larger spuds. | |
| 85% (Best Buy) | This was a Best Buy for patio pots last year and is made from composted woodfibre, bark and coir. | |
| 83% (Best Buy) | The geraniums were impressive, with huge plants that bloomed all summer. The potato harvest was among the best. |
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Our expert test of controlled-release fertilisers shows you which will keep your patio pots and hanging baskets looking good all summer long.
These peat-free composts are Which? Don't Buys
Unfortunately, not all peat-free composts are created equal. Thanks to our rigorous tests, we uncovered some bags that simply aren't worth your money. They failed to grow good plants and should be avoided.
Log in now or join Which? to unlock our full table below.
| Peat-free compost | Which? test score | Our verdict |
|---|---|---|
Sign up to reveal Get instant access to this and all our scores and recommendations Unlock tableDigital first month £5, then £8.99 per month, cancel at any time. Already a member? | 40% (Don't Buy) | The pack states it has enough feed to last three months, but our plants ran out of feed early on and didn’t bounce back when we started to liquid feed. |
| 38% (Don't Buy) | The geraniums were the smallest in the trial, but improved with a CRF. The potato yield was acceptable. | |
| 34% (Don't Buy) | Without CRF, the geraniums were tiny but very good when given fertiliser. The potato yield was the lowest by far. |
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Get instant access to this and all our scores and recommendations
Unlock tableDigital first month £5, then £8.99 per month, cancel at any time.
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The bottom line
'There are some great peat-free composts available to gardeners, but too many are poor. They're often made by the largest manufacturers, whose products fill garden centres and DIY stores. Gardeners deserve better.
'Last year was a particular low point. Which? Gardening found weedkiller residues in several composts. This is usually associated with green compost made from green-bin collections containing lawn clippings treated with auxin-based herbicides.
'Which? Gardening also looked at whether compost bags were being completely filled. Almost one in three of the products we tested had less than 85% of the stated quantity. We would expect a much higher proportion of composts to contain the correct amount.
'Which? Gardening will continue to test composts and press manufacturers to do better by gardeners.'
Adele Dyer, principal researcher & writer
To see our full list of recommended watering cans, check our guide to the best watering cans.
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