Trago Mills has been ordered to pay almost £200,000 in fines and costs for illegally dumping and burning waste at two of its out-of-town sites near Newton Abbot and Liskeard in Devon.
The Environment Agency took action after several thousand tonnes of waste, including asbestos, were found at the sites.
Agency officers who visited the Newton Abbot store found landfilled soil, stone, plastic, electrical goods, broken paving, tiles, concrete, wood, packaging, broken dustbins, old office kit and hazardous waste such as wood preservative.
A larger area of landfill, containing around 6,200 tonnes of waste including 200 sheets of asbestos, was found on an adjoining part of the site. Materials had also been burnt in a large pit.
In June 2009, helicopter video footage showed a stockpile of waste in a wooded valley near the River Fowey. The area was 1km from the main Trago Mills store at Liskeard and out of public sight.
The court heard that Trago Mills had an annual turnover of £85m in 2008 and made a pre-tax profit of £4m. The company has since worked with the Environment Agency to remove the waste and said the clean-up cost the business almost £500,000.
At the magistrates' court in Torquay, Trago Mills (South Devon) and Charles Robertson (Developments) pleaded guilty to five offences of illegally depositing and disposing of waste and were fined £185,000 and ordered to pay £14,558 in legal costs.
Trago Mills director Andrew Nunn said the board of directors, based at Liskeard, was unaware established waste-disposal protocols had been "deviated" from under a senior manager at Newton Abbot who was no longer with the company.
"Once the issue had been identified, we cooperated assiduously with the agency and at enormous cost to restore the site. We implemented a detailed programme of works, which was highly commended by a senior environment officer."
The business came 69th in Garden Retail's top 100 garden centre's survey.
HTA waste policy
"You need to take a responsible approach to waste management and disposal and we have made arrangements with third-party contractors for HTA members to comply with legislation on the disposal of batteries, waste packaging and waste electrical and electronic equipment."
Gary Scroby, policy manager, HTA