Whenever I’m back in London, I find myself daydreaming about what life would be like if I still lived there. My mind turns quickly to what I could grow more easily in that imaginary urban garden than here in Devon. Perhaps surprisingly, urban gardens tend to be much more hospitable places to grow than rural areas. The buildings, roads and other infrastructure store, reflect and radiate the sun’s warmth, creating a microclimate that is usually warmer than the countryside. Houses, fences and walls provide valuable shelter. The seemingly small advantages within this microclimate can make a real difference to what you can grow. As well as tomatoes, chillies, sweet peppers and aubergines, there are many delicious, marginal perennials that can thrive in an urban garden too. A couple of extra degrees may encourage figs to fully ripen, the shelter can help apricot blossom escape late frosts and cold spring winds, and the residual heat released by a south-facing wall can take a nectarin...