This article from Worldchanging provides a good insight and relevant links into the growing (sorry) Guerilla Gardening Movement, particularly in the USA:
The popularity of guerrilla gardening is growing. National Public Radio recently covered two stories on the subject, one on American seed bombing and another on night-time planting in London. We’ve covered guerrilla gardening at Worldchanging before (as well as the related topic of public food foraging and mapping), so we thought you might be interested to know about a new guerrilla gardening tool: tech savvy seed bombs that use biodegradable casings and are available at Etsy shops, ice cream trucks, grocery stores, and even vending machines! You can find seed bombs with local varietals categorized by geographic regions in the U.S. at Visualingual’s Etsy shop and at Anthropologie.
Common Studio founders Daniel Phillips and Kim Karlsrud have given new life to Karlsrud’s father’s old gumball machines and turned them into seed bomb dispensaries in a project they call Greenaid. For a quarter and a turn, the Greenaid vending machines dispense seed bombs made up of clay, compost and seeds to guerrilla gardeners in California, Minnesota, Illinois, and North Carolina.
Read the full article by My Tam Nguyen and Amanda Reed.