"Guerilla gardening has been given its name because it's not about going through tonnes of red tape to ask the Government permission to do something with the land they've ignored or forgotten about. Guerilla gardening is about taking matters into your own hands to make your surroundings a better place to live.
As a guerilla gardener you can be part of a fully–fledged green army taking on mighty battles with the city landscape, or a lone warrior of peace making small changes here and there. You can bring green to the urban desert in a full–scale or small–scale way. You can grow a seed in a pot at home then replant it somewhere in your city, or you can join a guerilla gardening association (there are loads around) and take over a bit of wasteground, turning it into a living green community space."
(Magda Knight)
http://www.guerrillagardening.org/index.html