Peter Gibbs and the panel are at Morden Hall Park, London. Christine Walkden, Matt Biggs and Juliet Sargeant answer the horticultural questions. This week, the panellists suggest some cascading plant ideas for a flat roof, as well as offering up tips for starting an orchard and musing over the fascinating history of growing holly next to oak trees. Horticulturalist at Morden Hall Park, Jade Wall, takes the team on a tour round the park's Edwardian rose garden, willow wood, and the wetland fed by the river Wandle. Producer: Jemima Rathbone Assistant Producer: Bethany Hocken A Somethin' Else production for BBC Radio 4