Terumot, Chapter Ten, Mishnah Six
The mishnah continues to deal with laws concerning fenugreek.
1) If one had bunches of fenugreek of mixed seeds of the vineyard, they must be burned.
2) If he had bunches of fenugreek of untithed produce, he must beat them and calculate the amount of seed within them and set aside [terumah] from the seed, but he need not separate terumah from the stalks.
3) But if he did set aside [the terumah from the stalks before he beat the bunches] he must not say: I will beat out [the seed] and take the stalks and give only the seed but he must give the stalks together with the seed.
Section one: Seeds that grew in a vineyard must be burned. Since this rule applies to the stalks as well as the seeds, all of the fenugreek must be burned.
Section two: The stalks of the fenugreek are not obligated in tithes or in terumah. So if he has bunches of fenugreek what he should do is beat them and thereby separate the seeds and then estimate how much he has to give to terumah from the seeds. He need not take the stalks into account.
Section three: If he declared the terumah before he beat out the seed, he cant go back and say that only the seeds will count for terumah. Once he has declared that there is terumah in the stalks as well as the seeds, he will need to separate terumah from the stalks together with the seed.