Which? said to give the Homebase product "a very wide berth", adding: "In 6 weeks our test plants had hardly grown from the time they were potted up."
A Homebase representative said it had sold 200,000 bags of the compost in 2009 and that its product had outperformed many industry rivals: "Homebase multi-purpose peat-free compost was launched in January 2009 following extensive trials. The trials included comparisons to other peat-free composts on the market. It compared favourably performing well above average and ranked higher than other retailers own brand peat-free multi-purpose composts and Scott's Miracle Gro peat-free multi-purpose compost equivalents. It is ideal for pots, hanging baskets, beds and borders as stated clearly on front of packs.
"Homebase multi-purpose compost is only one of a wide range of growing mediums offered to customers. We stock both peat-free and peat-based own brand in addition to supplier branded composts to cover the various requirements and preferences of gardeners.
"Additionally, on the back of pack we explain this compost is specially formulated for use in all outdoor containers and hanging baskets. For sowing seeds we offer a variety of options, we recommend Homebase John Innes No.1 Compost for potting on cuttings, seedlings and other young plants.
"We are planning for our normal externally controlled and audited growing trials again this spring where we test all of our range versus a significant number of products available in the market place. We will re-test our peat-free compost against other peat-free composts on the market and make any necessary formulation changes to ensure the product meets the quality we would require of a Homebase-branded compost.
Homebase said the tests compared 21 samples of various industry growing-media packs. After two weeks the Homebase product scored: petunias — 2nd best of 21 and Impatiens 6th best of 21, higher then the B&Q and Focus peat-free multi-purpose composts and Scott's Miracle Gro peat-free multi-purpose compost equivalents in these tests.
B&Q Multipurpose (88%), B&Q Sowing and Cutting composts and New Horizon Organic and Peat Free Growbag (both 71%) all received "best buy" awards for seed sowing composts, while B&Q Multipurpose (88%), B&Q John Innes No.2 (83%) and Westland West + Multi Purpose Compost (83%) were given "best buys" for growing on small plants.
But Which? Gardening awarded "don't buys" to Homebase Multipurpose Peat-Free and Vital Earth Seed and Cutting Compost (38% for seed sowing/54% for growing on young plants).
Which? Gardening head of research Richard Gianfrancesco said: "As our rigorous research has shown, choose well and young plants should thrive, but pick the wrong compost and you could end up with plants that either look sickly and unhealthy, or simply don't germinate at all."
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