One hundred years on from the inception of the RHS Chelsea Flower Show, our cities have grown in size both upwards as well as outwards. However as Professor Nigel Dunnett explains, this shouldn't stop you from trying your hand at having a garden or cultivated outside space. His rooftop garden this year celebrates 'skyrise greening' and looks at water management in a wonderful living, outside/inside spatial experience. Tom Hart-Dyke also scours the Great Pavilion for top tips on plants for unusual spaces and challenging conditions whether it be soil, shade or damp as he goes on a hunt to bring us the best plants for tricky environments.