I was at the Union Square Greenmarket today.The stand that has epazote is Pfaffenroth's. Today they were at the NE corner, next to Terhune's Peaches, which are fabulous.
They didn't have any epazote today, they said they had picked one patch and were waiting for the next one to be ready, but they will be having it again.
He said it was good for flatulence and de worming.
I have seen fresh epazote at the Union Square Greenmarket, on Saturdays, at the stand with the lettuce, beets, etc nearest the southwest corner of the market (where all the construction is). I think they are there on other days, but maybe at a different location.
There is a small Mexican grocery on 9th Avenue, in the upper 40's or lower 50's, on the west side of the street, next to the video store. I once stopped in and asked, and they said they had it, but I have never bought it there.
re: ruth arcone
If you happen to be at Sripraphai and you want to make it a 2 birds with one stone affair, right around the corner on Roosevelt Ave there is a combo restaurant and store called El Mexico which stocks all kinds of useful things for Mexican cookery, corn husks, masa harina, nopales, tomatillos, a large selection of dried herbs, a variety of Chiles and lots more. The guy behind the counter assured me that they will be getting fresh epazote this Friday, so I guess they occasionally get that in too. Haven't tried the restaurant though. Not sure if we could manage going to that particular block without eating at Sri.