The Advisory Committee on Pesticides (ACP) has given the all clear for a chemical to be reintroduced to the market, despite fears it damages vegetable crops.
According to the Royal Horticultural Society (RHS), Aminopyalid has been found to contaminate gardens and allotments.
The Dow AgroSciences product was taken off the market in 2008, but the ACP has said it is satisfied that new measures, which include educating farmers on its correct use, will cut the risk of damaging plants.
Dow AgroSciences principal biologist for grassland herbicides Andy Bailey explained that if the correct procedures are followed, there need be no harm caused.
"However, it remains good practice to know the provenance of any manure as other materials can contaminate manure," Mr Bailey added.
Meanwhile, the Italianate gardens and pleasure grounds owned by the founder of the Westonbirt Arboretum in Gloucestershire are now open to the public to help raise funds for their restoration, the RHS revealed.