Writer and historian Andrea Wulf talks about her recent book, The Brother Gardeners: Botany, Empire and the Birth of an Obsession, that traces the origin of the English country garden through the collaborative effort between two men and two countries: American farmer, John Bartram, and London cloth merchant, Peter Collinson. (Added to Monticello Podcasts on Aug 6, 2009. Approx. 44 min. )