The Guerrilla Grafters are a group of botanical dissidents who are covertly grafting branches of fruit trees onto ornamental trees in SF.
"There’s a group of gardeners in San Francisco that are spreading organic graffiti across the city. How? By grafting branches from fruit trees onto ornamental trees that have been planted along sidewalks and in parks.
They are using a very simple tongue in groove splice that’s held together with annotated electrical tape. Good luck to them."Info from BoingBoing: http://boingboing.net/2012/09/25/guerrilla-grafters-covertly-ad.html