Compost packaging should carry information showing when it was made, because old compost is less effective than it should be.
So says consumer organisation Which?, which also found that retailers are still selling old compost to gardeners, despite reporting on the practice last June. Then, it found old bags of compost for sale in a number of garden centres, which defended themselves by saying the old stock was there because of the previous year's bad summer.
However, Which? has found old stock of B&Q, Miracle-Gro, J Arthur Bower's and Westland compost still being sold this year.
"The nutrients in compost can degrade over time," it says, "so using compost that is more than a year or two old could prevent your plants from thriving."
B&Q confirmed to Which? that bags of own-brand compost in one of its stores were "really old stock" but that customers could identify out-of-date product by its marked-down price. It also said: "Our new stock is identifiable by the new Verve packaging."
However, Which? believes gardeners would struggle to tell old stock from new, and is calling on manufacturers to put a production date on the packaging.
The Growing Media Association told Which? that its members manage stock well but that if consumers are unhappy with their compost they should take it up with the retailer.
Which? thinks many gardeners would fail to realise that their compost was the problem if their plants were not growing well.