Mishnayos Maaser Sheni Perek 2 Mishnah 3

תאכל צמחונים – when they are moist vegetables and he should not leave them alone until they grow and they will not be appropriate for eating, but Terumah can be eaten whether as buds (directly from the capsules before they are dry) or as dry.

ב"ש אומרים: כל מעשיה בטהרה – even though fenugreek is not a complete food, and Terumah does not apply to it other than for the fact that it is eaten by some people, therefore, it is eaten in defilement; nevertheless, according to the School of Shammai, it is necessary that all of its preparations must be done in cleanness/purity, and with washing of the hands according to the law of all the rest of Terumah foods, for whomever comes in contact with them must first wash their hands. And the reason is in order that they would know that they are Terumah and that they should not be fed to foreigners (i.e., non-Kohanim).

חוץ מחפיפתה – hat without washing of the hands, one can comb the head with it, for it was their practice to comb their heads with fenugree.

כל מעשיה בטומאה חוץ משרייתה – [steeping it] in water, that it is necessary to steep/soak them in ritual purity, for if he steeps them without the washing of the hands, their steeping makes them fit to receive impurity. And he defiles them immediately in his hands, and they forbade this alone because of the recognition in order that they would know that it is Terumah/Priest’s Due.