Gardeners across the country are complaining of plants dying in composts based on substitutes for fresh peat.
Reasons include poor delivery of nutrients and even poisoning by pesticide traces in recycled “green waste”.
The problems raise questions about Government deadlines for eliminating the use of fresh peat in England, prompting calls to allow digging to continue at a sustainable level and tax it to build a rescue fund for areas with the best chances of being returned to bog.
Mike Prest, a retired nurseryman in Knaresborough, helps organise the horticultural section of the Great Yorkshire Show and visits many more shows as a representative of gardening suppliers.
He said: “A lot of gardeners are having problems they don’t recognise as being due to compost. A percentage of those available at the moment are not fit for purpose. You put your precious plant in it and it dies.
“Most gardeners think they have done something wrong, or the weather has been bad, or some bug has eaten the roots, but it has become clear to me and others that the quality of compost has deteriorated so much it has become a gamble to buy a bag.
“I know a lot of exhibitors of chrysanthemums and vegetables and they have to be very precise and they have always used a particular brand because they thought it was reliable. Now they are finding there is no amount of food in it or the nutrients are tied up by the other materials in it or, worst of all, it is all being taken by the weeds that are in it.
“I know a professional grower who lost a quarter of a million pounds’ worth of plants and when he had his compost analysed, he found 25 different fungicides and herbicides and insecticides in it.
“Even if it is only one in 10 which is a problem – and I think it is more like one in five – it is detrimental.”
In 2008, Susan Garrett, of the Green Lane Allotments Association in Horbury, Wakefield, sounded the alarm about weedkillers persisting in farm manures. Her campaign for tighter controls put her in touch with amateur growers’ watchdogs around the country and her impression is that three bags of compost out of 10 are unsatisfactory.
Gary Scroby, policy manager for the Horticultural Trades Association, representing the growers, said they were discussing all the issues with a taskforce which is consulting on the Defra targets for phasing out peat.
He said: “For the amateur sector, it will be important to reassure the consumer that alternative products can perform as well as peat-based products.
“The supply, sustainability, cost and quality of alternative ingredients all need to be carefully assessed to ensure a way forward that maintains the competitiveness of UK horticulture in an open market.”