You can take a peek at Cranford Park's 'secret garden' and help planting on Sunday (April 21).
A volunteer and viewing session, organised by the Friends of Cranford Park, will be held at the garden, beside the park's historic stable block, from 10am to midday. Tools will be provided.
Sunday also sees the launch of a three-stage trek from the source of the River Crane to the Thames.
The first leg of the walk, organised by London Wildlife Trust and FORCE (Friends of the River Crane Environment), will leave from Headstone Manor, in Pinner View, Harrow, at 10am.
To book a place on the free walk, call Andy Willmore on 0789 1004 098 or email firstname.lastname@example.org.