Here's an old thread for reference:
http://www.flyertalk.com/forum/showthread.php?t=308251

cordelli, not everything in Union Square is organic, but the people who work at the stands are usually happy to tell you if it is or not.

While Union Square is the biggie of the NYC markets, there are many others throughout the city--you can see the schedule and map here:
http://www.cenyc.org/site/