I don't know the history of the garden, but in Ben Affleck's The Town some key scenes take place in the Charlestown community garden (can't find a link to the garden on line, but Google gives some possibilities and the picture link shows it's rather lush. Cynic that I am I'll be interested in the director's commentary on the garden.
The food movement loves to embrace urban farming. That's fine, if there's a vacant lot, if you don't have park money the best use you can make of it is to open a community garden. It's good for the community and good for the environment.
However, and you knew there was a however coming, the environmental benefits of the urban setting come from density. New York City is one of the best places to live to have the smallest impact on the environment, simply because it's efficient to live and work in dense places. (Recently there's been challenges to the benefits of telework because it might be more efficient to heat and light offices for 1,000 people than 1,000 homes each with its own officeworker working from home, even considering the costs of commuting.)
The market tells us it's not efficient to have permanent farms in the heart of the city. I'm enough of a conservative to believe it.