Our tests have uncovered two great peat-free composts for containers, but you’ll have to pay more for them for some other composts. Only Which? carries out independent tests to find the best composts for containers, sowing seeds and raising young plants.
Buying the right compost will make the difference between pots overflowing with flowers and ones where the plants struggle to survive. So we think it’s worth paying more for a Best Buy compost for containers that will give you great value for money over the summer.
Most gardeners would rather use a peat-free compost if it grows great plants, but in our tests many fail to do this. Harvesting peat can damage delicate eco-systems and releases greenhouse gases.
Find out which composts we think are worth buying in our full compost test results.
Composts worth paying for
We found there were huge differences in performance between our best and worst composts, so it’s definitely worth paying a few pence more for a good one.
Our best composts for containers all grew fantastic bedding plants and had the heaviest crops of potatoes. Which? compost expert Adele Dyer said: ‘The pots on my patio give me months of enjoyment through the summer and so I will happily pay more for a compost that will sustain my plants, but is also a sustainable, responsible, peat-free option.’
Rising compost prices
Many of us are used to going to the garden centre to buy three bags of compost for £10. However, prices have remained the same for many years and there is speculation that they may rise soon.
Chairman of the Growing Media Association, Steve Harper, said: ‘Manufacturers can produce high-quality performing peat-free products but they do cost a bit more and the bigger question is are retailers and consumers prepared to pay the premium?’
Poor peat-free composts
If we’re asked to pay more, we need to know we’re getting great value for money, but in our trials we found some truly shocking peat-free composts that contained chunks of wood and had almost none of the essential nutrients needed to sustain plants.
All composts for home gardeners should be peat-free by 2020, according to a target agreed between the government and compost manufacturers. However many manufacturers are now shifting focus to ‘responsible’ composts which blend peat and peat-free ingredients, which are cheaper and easier to make. Read our guide on peat-free composts.
From 2017 composts will be assessed and audited through the Responsible Sourcing & Manufacturing Scheme for Growing Media. This will calculate a score based on the environmental impact of all stages of harvesting and transporting compost ingredients, but it may be a while before this information is available to home gardeners.
What makes a great compost?
Only Which? carries out independent tests of composts every year. We grow bedding plants and potatoes from four months every summer to find the best composts for containers, and test poorly performing composts to find out exactly why they have failed to grow great plants.
The bedding plants should grow into large plants and flower prolifically. We also look at the overall healthy of the plant. We weigh the potatoes and count how many small, medium and large potatoes we have harvested. Ideally we will have plenty of medium and large potatoes, rather than lots of small ones. We also look for smooth skins and take marks away for scabby potatoes.
We buy compost from four areas around the country to make sure the quality is consistent. Find out how we test compost.