Penelope writes: "Are they sold at the Greenmarket?"
Yes, certain farmers, particularly organic farmers,
have them, usually packaged in little plastic bags or
take-out containers. You might try D'Attolico's Farm
(Friday and Saturday, I think), Blooming Hill Organic
(Friday only), or Keith's Farm (Wednesday, Friday, and
Saturday, but Keith is only there on Saturday). Be sure
and ask if you can order a larger quantity; other
markets than Union Square might be good to ask farmers
as well. On Mondays there's an organic farmer at Union
Square who has flowers too, I believe.