"Crack garden" is probably giving you some interesting mental images. In reality, it refers to plant life that is squeezing up through cracks in our streets, sidewalks and parking lots against all odds. Some people are harnessing these tiny access points to soil in areas where they would otherwise not be able to garden. I suppose it's a form of guerilla gardening, but not quite the same.
I first learned the term from de LaB when I was reading about a workshop they were giving at Homegirl Cafe, a local non-profit restaurant. They were giving a brief tour through Los Angeles' Chinatown to show where produce is literally growing out of cracks in the pavement.
It's an interesting idea and I started looking for more information about it. I discovered that the rogue tomato plant growing along an improbable industrial fence line wasn't the extent of it. Parsley growing in the gutter of a busy metropolitan street, corn sprouting in back regions of a parking lot. Even one of the newer parks in Los Angeles is nicknamed The Cornfield because of the trains that use to traverse the space, dropping seeds that would later sprout.
Tokyo Green Space is finding inspiration in the creative use of small urban spaces, integral to the Japanese psyche, as pictured above.
(Images: Tokyo Green Space)