Monty Don and the team celebrate the start of summer as they indulge in the stunning array of colour and scent beginning to take over our gardens. Carol Klein continues her celebration of great plants and the people who champion them. In this episode she's with Billy Carruthers in West Lothian, enjoying his wonderful and varied collection of flamboyant peonies. Joe Swift visits world-renowned opera venue Glyndebourne, in Sussex and is given an exclusive, behind-the-scenes tour of their gardens only days before the opera season begins and the gates open to the public.