New York Times: Urban gardening used to seem subversive. People planted tomatoes in public parks, strung their hops to rooftops to make homebrew and reclaimed empty lots as community farms, never mind the property owner. Yet here in one of the more thoroughly tilled cities in America, subversive has come full circle: the federal government plans to plant its own bold garden directly above a downtown plaza. As part of a $133 million renovation, the General Services Administration is planning to …