(Rav Chisda): If a person declared his standing crops to be Hefker (ownerless) and then acquired them again and (harvested them and) separated Terumah from them, it is valid Terumah. If he declared (detached) ears to be Hekfer and then acquired them again and separated Terumah from them, it is invalid Terumah.

What's the difference between standing crops and ears? Standing crops - if before he declared them Hefker, he separated Terumah from them; it is invalid Terumah (since it was separated whilst still attached to the ground). Ears - if before he declared them Hefker he separated from them Terumah, it is valid Terumah.

(Rav Chinana citing Rav Chisda): There is a similar difference between standing crops and ears in the laws of Hekdesh.

The Rabbanan disagree with this - R. Yochanan cited from R. Yannai - the pasuk states (Devarim 14:29), "And the Levi will come, as he doesn't have a portion or inheritance with you'' - you are obligated to tithe from that which you have and he does not have. This excludes Leket, as his hand and your hand are equal in it (since a poor Yisrael is also permitted to take it). The same is true for Leket, for Shichechah, for Peah and for Hefker.

(R. Yochanan): The Bnei Chaburah asked - Since Hekdesh is prohibited both to the owner and to others; just as you learned from the pasuk that Leket is exempt since his hand and your hand are equal in it, you should also exempt Hekdesh from Ma'asros?

(R. Ila): What's the case? If he smoothed the pile (thereby obligating it in Maaser) whilst it was Hefker or it belonged to Hekdesh, the pasuk says (Devarim 18:4), "the beginning of your grain'' but not Hefker or Hekdesh grain.

Rather, the case is when he declared ears Hefker and then again acquired them - Hefker is exempt; but such a case of Hekdesh is obligated.

Hefker is exempt, as R. Yochanan cited above from R. Yannai, that we learn it from the pasuk, "And the Levi will come etc.''...This excludes Hefker produce, that your hand and his hand is equal.

Hekdesh is obligated, as the Mishnah (in Peah 4:7) teaches, "If a person consecrated standing crops and redeemed them as standing crops, it is obligated in Maaser.

Why is Hefker different from Hekdesh? Hefker left the possession of the owner (so everyone's hands are equal in it); Hekdesh didn't leave the possession of the treasurer.

(R. Avin): Hekdesh didn't fully leave the hands of the owner, since he has the first right to redeem it from Hekdesh.

(R. Zeira/ R. Yasa citing R. Elazar): One who sows a Hefker field is obligated in Ma'asros.

R. Yona would say that it's specifically when he acquired the field and its growths that it's obligated in Maaser; otherwise it's exempt.

Question (R. Chiya bar Ada to R. Yochanan): Are toadstools and mushrooms obligated in Ma'asros?

Answer (R. Yochanan citing R. Sisai): The pasuk states (Devarim 14:22), "You shall tithe all of your seed crop'' - something that is planted and grows - this excludes toadstools and mushrooms that grow without being planted.

R. Yona expressed it by saying that they are exempt because they do not draw nutrients from the ground (but rather from the air).

(The Mishnah taught that) even if it's normally left (in the ground) to grow further, whether he picked it earlier or later, it is obligated.

The Gemara points out from there, that it's specifically if it begins as food and ends as food that it must be tithed from the beginning; but if it begins as food and he doesn't normally leave it to grow further (as it doesn't end as food), he is exempt from tithing if he picked it at any stage, even at the beginning.

(R. Imi citing R. Shimon ben Lakish): The Mishnah was worded that way to exclude the opinion of Rabban Gamliel, who teaches in a later Mishnah (end of Perek 4) that the buds of fenugreek, mustard and white beans are obligated in Ma'asros (even though they are planted for their seeds, since they are eaten).

Question (R. Yosi): Is it because their buds are eaten that Rabban Gamliel obligates them? If so, even their leaves should be obligated?! Rather, Rabban Gamliel says that the buds are considered an independent food and the Rabbanan disagree.

Support (Baraisa - R. Yehoshua): I never dared to say to someone, "Go and pick for yourself buds of fenugreek, mustard or white beans and cook them'' to exempt them from Ma'asros. (He was concerned for Rabban Gamliel's opinion that the buds are considered food and obligated in Ma'asros.)

(Tosefta): Anything that begins as food but does not end as food (is obligated at the beginning but not at the end).

Question: What would be an example of that?

Answer (Baraisa): One who leaves a full row of Echro'a growing in order to use it for sowing, since others don't do that, his opinion is negated and the vegetable must be tithed. But if he leaves single stems for this purpose, since others do so, they are exempt from Maaser. (Echro'a is something that begins edible and then becomes inedible.)

The first teaching of the Baraisa applies when he picked them when they were still an edible vegetable, but not after they stiffened and became inedible. Is wood obligated in Maaser?!

The Mishnah taught that anything that does not begin as food but ends as food is only obligated when it actually becomes food.

Question: What would be an example of that?

Answer: (The next Mishnah teaches) When are fruits of the tree obligated in Ma'asros? Figs (are obligated) when their tops turn white (i.e. when they begin to ripen).