The £30m scheme at the site of the former Worsley New Hall is to go ahead after the government confirmed that it will not call in the plans, which were approved by Salford City Council last month.
The 154-acre project is a key part of a strategic 10-year, £160m investment programme announced by the Royal Horticultural Society in 2014, which set in motion a search for a fifth RHS garden in a part of the country where the society is unrepresented.
Salford city mayor Paul Dennett said: “RHS Garden Bridgewater will not only bring the historic grounds of Worsley New Hall back to life, but will also create jobs and business opportunities for the local area.
“The fifth national garden will be a national and a community asset, and a key example of green infrastructure in Greater Manchester, creating a real public amenity within our green-belt.”
Sue Biggs, director general of the RHS, said: “We are delighted with this hugely positive news, which will allow us to progress plans for the biggest gardening project in Europe and create our first new garden in 17 years.
“This news means we can fully embrace our ambition to create one of the most beautiful and inspiring gardens in Britain.”
The RHS has already installed a small team at the site, which is owned by Peel Land & Property, to move the project forward.
The plans include designs for a new Welcome building by architect Hodder + Partners, and an 11-acre walled garden designed by landscape architect Tom Stuart-Smith. Barton Willmore has worked on the project as planning consultant.