Along North-east Sandy Boulevard in Portland, Oregon, there’s a stretch known as the “Green Mile”. Here, medical marijuana dispensaries are budding. Almost two years ago, when Matt Walstaller opened Pure Green in the area, there was only one competitor. Today there’s close to 10. In the beginning business was booming, recalled Walstaller. But last autumn, Pure Green’s traffic started to slow. Since 1 October, when the sale of recreational marijuana was legalized, struggling businesses have found firm footing again.