The Breaker's Yard at Sutton House was an industrial site where cars and machinery were broken down for scrap until 2004. The trust bought it in 2005. The garden has been designed to offer play space for children, green areas for local residents and space to host events.
Project manager Christopher Cleeve said the trust is being more "diplomatic and playful", adding: "There are plenty of traditional formal flower and knot gardens. Why compete with them? We wanted to do something innovative that really meets the needs of local people."
The site's industrial history is reflected in the metal planters, recycled rubber furniture - some made from Harrier jump jet tyres by local craftsman Karl Smith - and tractor tyre sandpit.
Planters with box and lavender balls are a nod to the formal garden the house would have had. Children can pump rainwater into a rill that curves round the site or play in "The Grange", a two-storey caravan sculpture by designer Daniel Lobb fitted with a wooden balcony, fireplace and chandelier.
Hillier donated many trees and shrubs, Sparsholt College gave plants from its RHS Chelsea Flower Show garden and Copella provided apple trees. A bus, once used to transport royalty, is also being converted into a greenhouse and should be in place by autumn.
No horticultural staff will be employed at the site - maintenance will be carried out by volunteers and community groups. Professional horticulture help will come from the trust's properties in Hampstead and Richmond.