Westland Horticulture is to establish a Consistency Assurance for its compost range.
The West+ additive, first introduced in 2007, is now in its fifth generation and has been changed to deliver a finer grade.
Technical development head David Coop said: "We can offer this consistency message due to our raw material inputs. Our exacting standards mean we do not and will not use green waste in any of our growing media due to several performance factors. These include possible contamination risks from household waste, and much publicised weed killer damage from contaminated green waste and also inconsistent performance from bag to bag and region to region.
"Westland prides itself as being the gardeners’ champion and will continue to deliver the best performing compost both peat based and peat free. The further development of West+ highlights this."
"In 2013 more garden centre consumers bought Westland composts, than any other brand. In 2014 this looks set to continue, reaffirming the increasing demand from the consumer for consistent performance."
The Growing Media Task Force is working on a similar plan.