Nelson Mandela may have started it all when he was in prison—"A garden is one of the few things in prison that one could control," he wrote in his autobiography. "Being a custodian of this patch of earth offered a small taste of freedom."

But the idea probably rose to national fame only earlier this past decade, when the Garden Project of San Francisco started selling fresh produce to Alice Waters's acclaimed Chez Panisse restaurant. Catherine Sneed, the woman who in 1992 founded that project, which is a post-release program for ex-prisoners, did so because she had already seen such success with the Horticulture Program at the San Francisco County Jail, where she would go out on a daily basis with prisoners to work on the farm within the boundaries of the jail. The vegetables they grew were donated to soup kitchens and homeless shelters. Her moment of realization of a need for a post-release program came when one student of hers asked the visiting sheriff for permission to stay and work on the farm; Sneed recalled, "he had nothing on the outside."