The trees that line most city streets are pretty to look at, but they're not good for much else. Flowering trees that would normally bear fruit like pears or cherries are usually modified before being planted in urban areas. This saves city workers the hassle of potential clean-up by ensuring there’s no fruit to fall and rot. On the off-chance that you do come across a fruit-bearing tree on a city sidewalk, you might have an underground group to thank.

Since 2011, the Guerrilla Grafters have made it their mission to transform San Francisco’s sterile saplings into sustainable food sources. They achieve this by taking branches from fruit-bearing trees and grafting them to cuts made on host trees by using tape. They then assign locals to care for the trees and combat potential issues like pests or fallen fruit. 

The organization claims to have grafted about 50 trees in the Bay Area, with each effort being executed in secret. Though what they’re doing is technically illegal, the Guerrilla Grafters believe the benefits of their mission greatly outweigh the risks. “Guerrilla Grafters see a missed opportunity for cities to provide a peach or a pear to anyone strolling by,” the group says on their Facebook page. “The project may not resolve food scarcity, but it helps foster a habitat that sustains humans as well as non-humans.” For anyone looking to join the cause, an instruction manual [PDF] and a crowd-sourced map of trees that can be grafted are available on their website. 

[h/t My Modern Met]