Kilayim, Chapter Seven, Mishnah Two
The first section of this mishnah continues to discuss laws related to vines which have been bent into the ground, and then their heads brought up elsewhere to start new vines.
The following three sections discuss three instances where it is prohibited to sow seeds but if he does sow seeds, the seeds are not prohibited as kilayim.
1) One who has bent [and conducted underground] three vines, and their [original] stems are visible, Rabbi Elazar bar Tzadok says: if there is between them from four to eight cubits, they combine, if not, they do not combine.
2) A vine which has dried up, it is forbidden [to sow near it], but it does not prohibit [the seed as kilayim].
3) Rabbi Meir said: the same applies to a cotton plant, it is forbidden [to sow near it], but it does not prohibit [the seed as kilayim].
4) Rabbi Elazar bar Tzadok said in his name: above the vine too, it is forbidden [to sow near it], but it does not prohibit [the seed as kilayim].
Section one: A person has taken three vines, bent their ends into the ground, conducted them elsewhere and then brought them back up again. It now looks as if he has two rows of three vines, which in normal cases constitutes a vineyard (see 4:5-6). Rabbi Elazar bar Tzadok says that this constitutes a vineyard only if the old vines and new vines are four to eight cubits apart. If they are separated by more than eight cubits, than they are too far apart and hence dont combine. If they are too close together then they dont look like two different rows and since they are really the same vines, they dont constitute a vineyard. In these situations, he need only distance six handbreadths in order to plant seed. However, if the mother vine and its offspring are between four and cubits apart then they do constitute a vineyard and he must distance the seed four cubits from it.
Section two: A vine which has dried up does not have the same prohibitions connected to it as does a live vine. Nevertheless, because it is still a vine it is prohibited to plant seeds near it. If, however, one does plant seeds, the vine doesnt cause the seeds to become kilayim.
Section three: The same halakhah holds true for the cotton plant, which resembles a grape vine, and also is called tzemer gefen (literally, the wool of the vine) which is similar to the word for vine, gefen. It is prohibited to plant seeds in proximity but if one does, the seeds are not prohibited.
Section four: Rabbi Elazar returns to discuss planting seeds on top of the vines which are conducted underneath the ground. While it is forbidden to plant on top of these buried vines unless there are three handbreadths of soil, if he does plant seeds there, the seeds are not forbidden as kilayim.