Stinging nettles, buttercups, broken crockery, fly-tipped flowers and a discarded gnome are not the usual hallmarks of an RHS Chelsea flower show garden. But this year’s On the Edge garden by Sarah Eberle – the most decorated designer at Chelsea – is designed not to look like a garden at all, rather to transport its visitors to the liminal spaces on the outskirts of towns where the countryside begins and nature is in critical need of protection. “The garden is about the fringe lands of towns and cities – and how vulnerable they are to development,” said Eberle, who has created the garden for the Campaign to Protect Rural England (CPRE) to mark the charity’s centenary year.…