An 80 per cent peat compost produced by Petersfield and priced at £14.99 has been launched by Thompson & Morgan (T&M) as an antidote to what it calls "underperforming" green waste growing media that is causing customers' plants to fail.
But other manufacturers and the Growing Media Association have hit back, pointing out that their products are up to scratch and arguing that T&M is making "easy claims".
The Incredicompost product is made up of 80 per cent Irish peat and 20 per cent wood fibre. T&M said its compost trials were "a real eye-opener " and its testers were "shocked by the difference between the best and worst compost available", with cheap mixes containing "a high percentage of local authority-supplied green waste - a false economy".
T&M horticultural director Paul Hansord said: "We've been unhappy with the majority of consumer composts for several years now. So have many of our customers, who through no fault of their own have had problems with T&M plants because of the compost they have used. Launching Incredicompost, we are now able to offer a premium, professional grower-quality compost alongside our core seed and plant offering."
Bord na Mona UK consumer head Steve Harper said: "I guess that it will be a small player in the market given it appears to be mail-order for their customer base and at that price is never going to be mainstream.
"That said, I think there's always room for players that want to come into the market with good products and would welcome that.
He added: "It also shocks me how many poor composts there are on the market, but it appears to me that T&M are poorly informed about the reasons.
"Our peat-reduced and peat-free products using green waste regularly top the Which? trials. T&M, as with others that don't use it, just appear to want to point the finger at something to make a claim."
Harper said he is concerned about T&M claims on wood fibre, which he said can compress easily and "lock up nitrogen if not perfected - and most aren't - leading to poor growth".
Westland marketing director Keith Nicholson said: "We are not surprised by T&M's findings that green waste is a false economy for gardeners. This is something that we have already alerted consumers and trade to through our Compost Consistency Assurance campaign, which we began in February this year.
"At Westland, we're proud to have never used green waste. The ingredients in our composts include peat from our own controlled peat bogs that is blended with our patented West+ wood fibre ingredient. This ensures an open structure that allows excellent drainage and optimised root growth."
A Sinclair representative said its products did well in Which? tests, "are repurchased year after year by discerning gardeners and have performed remarkably well in our own trials this year". Sinclair uses composted wood to blend with peat.
- The International Peat Technology Symposium in Riga, Latvia, (25-29 August) is expected to host 230 delegates from 26 countries discussing restoration, harvesting and surveys.
Response - Growing Media Association
Growing Media Association (GMA) chair Jamie Robinson responded to the Incredicompost launch by saying: "It is easy to make claims about growing media and to make statements about existing competitor products on the market.
"However, to my knowledge Thompson & Morgan are not members of the GMA and have not been involved in all the talks on quality and peat content that resulted from the sustainable growing media project under the Defra initiative.
He added: "This initiative includes a protocol that has been developed to ensure that products are tested to a standard protocol and match a standard performance criteria.
"The GMA already has an existing audited quality standard, which ensures that members produce quality products, and we would recommend that consumers always purchase products from the association's members, where there is a good quality standard."