Pe'ah 076

2:
We must assume that once the poor were permitted access to the farmer's fields and orchards they would very quickly remove from there as much as they needed. If any produce was still left unharvested when the poor had taken all they wanted obviously it would not be left in the ground, on the tree or on the vine. Our modern logic would suggest, perhaps, that once the poor had taken all they wanted whatever remained would revert to the owner. But this cannot be because the Torah has specifically taken this produce out of his hands. Furthermore, from the purely practical point of view, it would not be sensible to let the produce revert to the owner: that would leave the situation open to great abuses, as we can easily imagine. Another alternative, of course, would be to let it remain until it rots; but the sages could not accept such a treatment of the foodstuff: the Torah [Deuteronomy 24:19] commands that the produce is to be left "for the foreigner, for the fatherless, and for the widow" – "and not for crows or bats" [Pe'ah 20d]. It is for this reason that any produce left unharvested by the poor becomes hefker, and belongs to anybody on a 'first come first served' basis. (For further details about the concept of 'hefker' see explanations on 6:1 [Pe'ah 059].)

3:
Thus the first clause of our present mishnah seeks to define the moment when any remaining produce becomes available to everybody, rich and poor alike. Firstly this moment is defined as regards leket. When our present mishnah is quoted in the Gemara [Ta'anit 6b] it includes not only leket but also shikheĥah and pe'ah. Thus it is clearly the intention of our mishnah to include all the poor dues that come from the field. This moment is defined as from the time when the last stragglers of the poor have left the field: when there are no poor people left harvesting the field whatever they have left is made available to anybody. One is left with the impression that in all cases the destitute collected their poor dues from the ground crops, the vegetable plots and the fruit trees in one fell swoop as it were. When the gates of the fields were opened the hale and hearty would surge forward, one imagines, and would quickly take their fill; but the field would not become available to the general public until the infirm and the aged stragglers had also left.

4:
The definition of this moment is different for the orchard. In the case of the grape harvest everybody is entitled to what is yet remaining from the moment when the destitute have worked the vineyard, departed and a second group has done the same (or the same poor have come a second time).

5:
This leaves the olive orchard. Tanna Kamma defines the moment when any remaining olives may be collected by anybody as being at the time of 'the second rainfall'. In Eretz-Israel rains fall in two seasons mainly – what are called in the second paragraph of the Shema 'the former rains and the latter rains'. The latter rains come at the very end of winter and in early spring and they are usually gentle showers. The former rains start some time after Sukkot. In tannaïtic times they would divide these earlier rains into three sub-periods. The first sub-period ended on 17th Marĥeshvan; the second was deemed to have passed one week later, and the last was seen as being over by the end of the month [Ta'anit 6a]. At any rate, Tanna Kamma permits allcomers to take whatever they can find in the olive orchards from 23rd Marĥeshvan.

6:
Rabbi Yehudah bar-Ilai has a different definition. He would not permit allcomers access to the olives until there was virtually nothing left: until a poor person would glean the olive orchard and could barely find olives that were worth four issars in the market. The issar was a Roman coin, though its value was so small that the Romans only used it in theory, their smallest actual coin being the sestertius which was worth two and one half issars. In buying power, in Eretz-Israel at that time, four issars were considered to be the equivalent of two meals – one for the poor man and one for his spouse. Halakhah, of course, follows Tanna Kamma and not Rabbi Yehudah.

With all due respect, 'luf' made no sense to me other than it grows underground. Now that I have heard it might be arum, that is about as useful as it is nothing I have ever encountered, not even when I lived in Israel.

I respond (with tongue in cheek):

And that is what God created Google for! Let me save you the bother:

You can read more at http://www.bartleby.com/65/ar/arum.html.