Kilayim, Chapter Six, Mishnah Six
Our mishnah returns to discuss the aris (espalier), the vines trained to grow on either a fence, another tree or in a ditch.
1) Gaps in an aris must be eight cubits and somewhat more [in order to be able to sow seeds in the gaps].
2) [In the case of] all measurements that the sages said in connection with a vineyard, there is no and somewhat more, except in the case of gaps in an aris.
3) The following count as gaps in an aris: if an aris was razed in its middle and five vines remained on one side and five vines on the other side. Then if the gap is [only] eight cubits, one may not bring seed there. [But if the gap is] eight cubits and somewhat more, they give [the vines] space to work them, and he may sow the rest.
Section one: If there are gaps in an aris that are more than eight cubits wide, then one can sow seeds in them.
Section two: The mishnah now makes a parenthetical remark that throughout Kilayim, whenever a measure was given, it was given precisely. If the Mishnah says that something has to be four cubits, it need only be four cubits exactly. However, in the case of gaps in the aris, there has to be a little more than eight cubits. The Tosefta says that the gap must be eight cubits and one handbreadth.
Section three: The mishnah now explains what gaps in an aris need to be in order to sow seeds there. There are two necessary conditions. The aris had to have originally had more than ten vines. The middle vines were then razed and there was left a gap in between the remaining vines that was big enough to plant two arisim, each of five vines. If this gap is precisely eight cubits (or less), then one cannot sow seeds in between. However, if the gap is more than eight cubits then he can leave space to work the remaining vines, and plant seeds in the middle. In mishnah one we learned that according to the sages, he needs to leave four cubits to work the remaining aris, whereas R. Yohanan ben Nuri holds that he need leave only six handbreadths.
We should also note that gaps in an aris are treated differently from the karahat, the empty patch in a vineyard, which requires sixteen cubits for it to be permitted to plant there (mishnah 4:1).