Organised by the London Parks and Gardens Trust, the weekend will take place immediately after the extended Diamond Jubilee Bank Holiday on Saturday and Sunday, June 9 & 10, 2012.
For the first time, the event will be in association with the National Trust.
Around 200 communal gardens, many that are not usually open to the public, will be taking part ranging from the historic to the traditional through to roof gardens and allotments.
Among the new gardens for 2012 and highly appropriate for the Diamond Jubilee year is the Queen Elizabeth Hall Roof Garden on the Southbank.
More information can be found at www.opensquares.org.