Mishnah 2 continues to deal with the subject of havrachah (layering) - taking a vine that emerges from the ground and replanting it in such a way that it comes up and emerges again at a second spot. Our Mishnah teaches that if this is done with three vines, one can ultimately create an entire vineyard out of them: for when the act of layering is performed, and the original spot from which the vine emerges is visible, and it also comes up out of the ground at a second spot - two vines have been made out of one.
Three vines that combine to form a vineyard:
Rabbi Elazar bar Tzadok says that everything depends on the gap between the first spot where the vine emerges from the ground and the second spot where it emerges: if the distance between them is between four amos and eight amos, they combine with one another to form a vineyard.
The reason is that in any vineyard:
Less than four amos: if the vines are four amos apart or closer to one another, they are too close.
More than eight amos: this is not considered a vineyard.
It emerges that if the distance is between four amos and eight amos, these three vines are genuinely considered six vines. But if the distance is not between four and eight amos, they do not combine with one another.
A vine that has dried up:
The Mishnah goes on to teach: a vine that has dried up - it is forbidden to sow next to it, but if one did sow and something in fact grew there, it does not become forbidden. The prohibition to sow stems from appearances alone, since the vine is no longer truly alive; and in terms of the matter itself, since it no longer grows, the sowing as such is fine.
The Rosh explains that if the leaves of the vine fell off even in the summer - even though in the summer it is supposed to have leaves - it would still be forbidden, because there are vines that lose their leaves even though they are alive, and even in the summer.
Cotton - 'Tzemer Gefen':
The Mishnah adds a further case of the same category, things next to which it is forbidden to sow, but where even if one did sow no prohibition is created: Rabbi Meir says that what we call cotton may not be sown next to, just as though it were a vine, but it does not become forbidden if one sowed next to it.
The reason for the name "tzemer gefen" - which literally means the wool of the vine - is that cotton resembles a vine in the way it grows. Therefore, because of the resemblance, one should not sow next to it; but if something grew there, it does not become forbidden.
Some understand this statement differently: it does not refer to a prohibition to sow next to cotton, but rather to sowing cotton next to a vine.
Planting above a vine that was layered:
It is further said in the name of Rabbi Meir that this same ruling - that the act is forbidden but does not create a prohibition - is also true of one who plants above a vine that was layered, that is, a vine that was placed under the ground in the act of havrachah. As we learned in the previous Mishnah, three tefachim above it are required in order to plant there; and if there were not three tefachim, then after the fact planting above the vine is forbidden - one may not plant there, but what grows does not become forbidden.
In summary: In this Mishnah we learned that three vines that were layered and whose original stocks are visible can combine and be counted as six vines, provided that the gap between them ranges from four amos to eight. We also examined three cases in which it is forbidden to sow because of appearances but the seeds do not become forbidden: a vine that has dried up, cotton, which resembles a vine in the way it grows, and planting above a layered vine without three tefachim.