My understanding is that most Ashkenazic communities today don't eat green beans on Passover, treating them as kitniyot (a bunch of legumes for which the custom arose to avoid on Passover). What's the earliest source/discussion on this?
Sefer She'arim HaMetzuyanim BeHalacha (published appx 1950), commenting on the Kitzur Shulchan Aruch (Siman 117, Si'if Katan 7), mentions that green beans and, apparently, peas, may be considered Kitniyos as well.
I have since found online in the name of Rabbi Elazar M'Vermiza רבי אלעזר מוורמייזא that he said in a Pesach Drasha that we do not eat "Polin V'Adashim" since there is wheat mixed in with them.
בדרשה לפסח של רבי אלעזר מוורמייזא הוא מספר בקצרה "ומה שאין אוכלין פולין ועדשים, מפני שיש בהן חיטין"