Is 'wildness' an inviolable concept, or with 7 billion of us on planet earth, is the whole world in fact a garden? And can we as gardeners make a difference to the fate of the planet and its biodiversity?

Hosted by the RHS at the Lindley Hall in London, the John MacLeod Annual Lecture has fast become a prestigious event, highlighting important and inspiring topics on horticultural science. This year, Professor Stephen Blackmore CBE, spoke on 'Gardening Planet Earth - Sustainable Horticulture'. Download this podcast to hear the lecture in full.