When Simon Olpin and his family moved to their house in Sheffield, England, 30 years ago, the garden was “a blank canvas”, he told the BBC. Over the years, Olpin has turned the canvas into an exotic jungle, with giant bamboos and Chinese palms. “It’s not a pretty garden full of pretty flowers,” he admits, adding that most of the plants have survived even the harshest of winters. Olpin, a scientist, developed his love of exotic plants on a visit to the Lost Gardens of Heligan in Cornwall, England. He is afraid of flying, so has never seen his plants in their native lands – only in Cornwall and his tropical garden in Sheffield.…