Reynolds is well placed to talk about guerrilla gardening, being comrade #001 (in the language of the book, he's Richard 001) in a movement that now has thousands of regular recruits from California to Cape Town. With actions that range from pranks to serious attempts to Feed the People, guerrilla gardeners are a worldwide phenomenon, and one with a serious agenda for social change, to which Reynolds' book is a thoughtful guide.
What all attempts at guerrilla gardening have in common is a deep challenge to property rights. If the gardening isn't illicit, if it isn't on someone else's land without his permission, then it isn't guerrilla—it's just gardening. Reynolds understands the history behind the idea of changing relationships to land. He quotes Che Guevara's observation that "it is tractor and tank at the same time breaking down the walls of the great estate ... and creating new social relations in the ownership of land."
Reynold's book is salted with aphorisms from Mao and Che, but the real eminence grise is Gerrard Winstanley, the True Leveller or, to use the more appropriate shorthand, Winstanley the Digger, the original guerrilla gardener. A Christian radical during the English Civil War, Winstanley held private property in vocal contempt. The 1649-1650 organisation, occupation, and cultivation of common land in Surrey with which he is most famously associated was ultimately undone by the authorities, but the spirit of the Diggers lives on, and Reynolds's coming-to-terms with Winstanley is one of the reasons to read On Guerrilla Gardening.
When I talked to Reynolds a couple of years ago, his main complaint was that "Winstanley made too much noise" and ended up alienating potential allies. Winstanley chose to speechify, rather than to sow. Reynolds sees the need for less political grandstanding, and more potted guile. Which is why his book is styled as a manual, full of sensible, practiced advice. If you're stopped by the authorities, for instance, try saying that the community wants to make the place nicer, and you're a volunteer. It's hard for people to stop that.
In addition to tactical insights, Reynolds also offers strategic advice, particularly about which common land to shoot for. In language that, at least half jokingly, summons the authority of a general at war, he says, "My recommendation is to focus your attack on neglected land. This is a tangible enemy, and an adversary against which you are more likely to win support." Part of the reason for the support is that, on neglected land, improvements will swiftly be noticed. A more beautiful and productive bit of green space is a victory for the movement and, pragmatically, nothing succeeds like success.
Of course, guerrilla gardeners aren't the only group to be taking on the challenge of reconfiguring our ideas about public space. Perhaps most spectacularly, London-based Reclaim the Streets did its own bit of guerrilla gardening in July 1996, when they took over London's M41 motorway, drilled into the concrete, and planted trees while 7,000 danced in the lanes.