The initial cost of creating the garden is £31.2 million. The RHS has committed £14.2 million to the project and Salford City Council £5 million.
A grant of £5 million came from the Garfield Weston Foundation to support the development of the historic 4.5 hectare walled garden at Worsley New Hall.
A further £500,000 was awarded by Arcadia, a charitable fund, to develop the garden’s lakes. The garden is due to open in 2020.
It was planted in the 1840s to serve the long-gone house. Little of the original planting remains, making its restoration hugely ambitious. Brambles and overgrown shrubs have been cleared.
RHS director general Sue Biggs said: "The walled garden and beautiful lakes are at the very heart of our ambitious plans to make RHS Garden Bridgewater in Salford one of the best in the country."