In front of an audience at the Hay Literary Festival Adam Rutherford talks to the botanist and Native American Robin Wall Kimmerer. In her book, Braiding Sweetgrass she shows the importance of bringing together indigenous wisdom and scientific knowledge, to increase understanding of the languages and worlds of plants and animals. Hugh Warwick is an expert on hedgehogs but in his latest book, Cull of the Wild, he focuses on animals less native, and beloved. From grey squirrels in Anglesey to cane toads in Australia he explores the complex history of species control, and the ethics of killing in the name of conservation. The writer Olivia Laing turns her attention to the efforts to create paradise on earth. In The Garden Against Time she retells her own attempts to restore a walled garden in Suffolk while investigating the long history of gardens – real and imagined, follies and pleasure grounds. Producer: Katy Hickman