We’ve heard of guerrilla gardening, and we’ve heard of grafting plants — but guerrilla grafting? That’s new to us. For the past few years, a group that calls themselves Guerrilla Grafters have been secretly grafting fruit-bearing scions onto ornamental, non-fruiting trees in San Francisco. City officials contend that Guerrilla Grafters are breaking the law, but their actions have been celebrated by proponents of urban agriculture. And they have been included in the US pavilion’s Spontaneous Interventions exhibit at the Venice Biennale.

The streets of San Francisco are lined with pear, plum and apple trees, but out of fear that the fruit would make a mess and attract rodents, the city intentionally planted sterile trees that don’t bear fruit. By grafting fruit-bearing branches on those trees, Guerrilla Grafters make fruit free and accessible to anyone who picks it. The group was started by Tara Hui, who started grafting fruit-bearing branches onto city trees a few years ago.

To graft a branch onto a fruit tree, all you have to do is make a slit with a knife in a brach on the host tree; insert a branch from a fruit-bearing tree, and secure it with tape. “Once it heals, it connects,” Hui told the LA Times. “Basically the branch becomes part of the tree.” Guerrilla Grafters use color-coded electrical tape to mark their handiwork, but they won’t disclose the location of their interventions to the press out of fear that the city will remove them.

With “undoing civilization one branch at a time” as their motto, Guerrilla Grafters consider what they do to be a radical act — and it is. Although it doesn’t solve problems of food scarcity, it’s a symbolic move towards making fresh food free and accessible to all. As the group explains, it’s one step closer to creating “a habitat that sustains us.”