Salad leaves

It's boom time in the world of lettuce and salad leaves. More leafy greens were sold in the UK last year than ever before, and that upward trend looks set to continue - driven in particular by bags and bowls of pre-prepared leaves. In this edition of The Food Programme, Dan Saladino goes on a journey into this fast-changing world of leaves - from how they are grown and packaged, to the ongoing hunt for new leaves. Dan discovers how one particular type of lettuce with roots in 19th-century America changed food forever, he encounters a man who travels the globe searching for the next 'hero leaf' - and learns secrets about preparing and growing. Along the way he'll meet pioneering chefs René Redzepi and David Everitt-Matthias, US food writer Irene Sax, greengrocer Charlie Hicks, as well as gardener and writer Mark Diacono.