Today, rifling through the multitude of guerrilla-gardening Flickr pages and blogs  discovering all the action in Amsterdam, Calgary, Turin, Tokyo or Long Beach  you can almost start to see this kind of vigilante greening as the instinctual human response to city living. In “On Guerrilla Gardening,” Reynolds describes gardeners he has met around the world through his own blog, guerrillagardening.org. (Its forum, where guerrillas plan “troop digs” and exchange advice, now has more than 4,000 registered users.) These include a sunflower specialist in Brussels; a founder of an unsanctioned community garden currently fighting eviction from vacant lots in Berlin; and the San Franciscans who converted disused properties into vegetable gardens, even pirating absentee owners’ water. Reynolds’s book is also full of references to horticultural “sleeper cells” and “shock and awe” plantings, and culls tactical advice from the writings of Che Guevara and Mao Zedong  though “I think Mao comes across far more kindly than I intended him to,” he told me regretfully.

Reynolds has helped build 28 gardens around London over the last four years. Unlike many guerrillas I spoke to, he is not building big community gardens, growing food or hijacking neglected, privately owned land to critique the capitalist system. Instead, he is planting strictly ornamental arrangements of flowers and shrubs on roundabouts, roadsides, tree pits and other slivers of public land that have fallen into disrepair. He is fundamentally an aesthete. And at first glance, there’s a confounding innocence to it all. Yet Reynolds has managed to stir controversy and, very recently, found himself surrounded by the police. He is quickly becoming both a subculture celebrity (Adidas sent him a treatment for a guerrilla-gardening-themed ad campaign) and a public intellectual, challenging ideas about what it means to live in a city  simply by decorating one.

Reynolds says that he has gardened with several hundred guerrillas in London and now hears of actions he had nothing to do with planning. A few weeks before the dig in Hoxton, a new acquaintance asked for his help reforming a muddy median near Camden’s Hawley Arms pub  a famed Amy Winehouse haunt that burned in a huge fire in February. “It’s been described here, very inappropriately, as the 9/11 of the indie world,” Reynolds told me. In the spirit of healing, guerrillas replanted the area with hedging donated by a woman in Notting Hill. (Reynolds gets frequent donations of plants and cash and says he spent about $1,400 of his own money on gardening last year.) They planned to prune the hedges into topiary the shape of Winehouse’s hairdo.

Reynolds calls such neglected plots “orphaned land.” Sometimes, as is the case with the plot in Hoxton, each relevant city agency assumes another one is responsible for the upkeep of a particular patch. Orphaned land is an abundant, underutilized resource in the postindustrial city, as is the creative energy of people like Reynolds who would love to garden but can’t afford land of their own. That is, even in cities where land is scarce and expensive, substantial amounts of it are left derelict. Thus, guerrilla gardening mobilizes gardeners without land to take over land without gardeners. A space that previously meant nothing to anyone is turned into “a catalyst for community conversation,” Reynolds says, generating a feeling of shared ownership of the city.

By now, most of his energy is devoted to looking after about a half-dozen established plots, keeping his work there from reverting into hives of overgrowth and litter. He and his girlfriend, Lyla Patel, often tidy up or weed at night, on their way home from pubs and parties. Patel, who is 27 and grew up in London, told me that the only times strangers have ever struck up conversations with her on the street are when she’s gardening.

Patel and I took the tube to Hoxton together since Reynolds’s car was packed with plants. She lovingly described him as easily impassioned and distracted  a classic dilettante, if he weren’t also an incorrigible overachiever about everything. Reynolds and his brother were briefly signed to a record label as an electronic-music duo, and along with a friend, he silkscreens and sells a line of T-shirts. One afternoon, he told me he was thinking about starting a one-man painting-and-decorating business to earn extra cash. The next day, he had a Web site up and his first job, redoing a bathroom.+