David Maxwell heads to the world famous RHS Garden Wisley in Surrey where he finds out about the important research and plant trials taking place. With curator Matthew Pottage he explores the exotic garden which was established in September 2017 and he heads to the national collection of Heathers where Peter Jones tells him why every garden should have one. Also in the programme, Helen Mark heads to Salthill Gardens near Mountcharles in County Donegal where Elizabeth Temple has created a beautiful walled garden over three decades.