Which? compost trials have found eight of the best composts around, but we’ve also uncovered a staggering 11 Don’t Buy composts for sowing seeds or growing young plants.
We tested 25 widely available brands and discovered huge differences between a Best Buy and a Don’t Buy compost. Our trials have also found a peat-free compost that excelled in both our sowing seeds and young plant tests.
Our tests can save you money, as paying more for compost won’t necessarily guarantee you good results. Some of the most expensive products, costing 45p per litre, were Don’t Buys – one of our Best Buys only costs 11p per litre.
To find out which composts will give your young plants the best start, and which you should avoid, click to see our full compost test results.
Peat-free Best Buy compost
Peat bogs are wildlife rich environments that are damaged, often beyond repair, when the peat is taken out. So we were thrilled when our tests uncovered a peat-free Best Buy.
Which? Gardening compost expert, Adele Dyer said: ‘This is a great step forward as by 2020 there will be no peat in composts for the home market, following a voluntary target set by government. It’s a welcome result to all gardeners who prefer not to use peat.’
To see which peat-free brand to buy, look at our Best Buy composts.
Almost half the composts are Don’t Buys
Great compost can make all the difference between a bumper crop of vegetables, fruits and flowers, and lacklustre plants that never look their best. Worryingly, almost half of the composts for raising seedlings or plug plants scored very badly in our tests.
Last summer was very hot and temperatures soared in our greenhouses, despite shading and ventilation. Yet while some composts were able to grow excellent plants, too many others produced weak seedlings and spindly, pale plants.
Finding the right compost is not just a question of looking at the packaging or even the compost inside, as you cannot tell how it will perform from looks alone. Neither can you rely solely on big names – our tests found Don’t Buys from premium brands.
Rigorous compost testing
We tested 25 composts for sowing seeds, raising young plants or both and tested them at a highly respected horticultural research institute. We sowed 14,400 seeds and raised 960 seedlings and small plug plants to discover which Best Buy composts gave consistently good plants. And to reveal the Don’t Buy composts that produced variable crops and plants that hardly grew at all.