Related על נדרים 116:1

One who pulls weeds among [terumah] leeks with a Gentile (alt., "with a Samaritan"), even though its produce is untithed, he may not* eat casually among the produce [of leeks]. [*Note: Ter. 9:7 has "he may eat casually."] Rabbi Shimon ben Elazar says, right after shevi'it (the seventh year of the agricultural cycle, when fields lie fallow), he is permitted [to eat casually if he is weeding alongside] a Jew.

He who weeds allium plants (whose seeds do not disintegrate) for a Gentile, even though the produce is untithed he eat from them in a casual fashion. Saplings of terumah which had become unclean and were re-planted, become clean from their uncleanness. But they must not be eaten until the edible part [of the stalk] has been lopped off. Rabbi Judah says: he must [before eating] lop off a second time that which grew on the edible part.