If garden tourism used to be exclusively for budding botanists, well, no more. Checking out a city’s off-grid green spaces is now definitely a thing, says Ruth Holmes, chair of London Parks and Gardens Trust, the organisers of Open Garden Squares (9–10 June), a weekend that lets visitors snoop around London’s usually off-limits gardens – including, it turns out, Downing Street’s. “We’re predicting 60,000 visits – up a third on last year.” But is it a real trend? Hip publisher Phaidon seems to think so. This month sees the release of Green Escapes, a comprehensive guide to the world’s “secret urban gardens”. So, what’s the city with the most urban greenery? Paris, surely? Close, but no. World Cities Culture Forum claims it’s Moscow. And that’s before the opening of the new, 13-hectare Zaryadye Park this year. It, too, has been a huge hit: 50,000 people a day, and counting.