Rav Asi said: The garden bed in the Mishna whose area is six by six handbreadths is one whose internal area is six by six handbreadths excluding the area of its boundaries, which must be added to the total area. That was also taught in a baraita: The internal area of a garden bed is six by six handbreadths.
The Gemara asks: How much is the size of its boundaries?The Gemara answers, as we learned in a mishna that Rabbi Yehuda says: The width of the border is like the width of a foot. And Rabbi Zeira said, and some say it was Rabbi Hanina bar Pappa who said: What is the reason for the statement of Rabbi Yehuda? As it is written: “And you water it with your foot like a garden of herbs” (Devarim 11:10), meaning that just as one’s foot is a handbreadth wide, so too, the boundary between garden beds where one walks to water plants is also a handbreadth wide.
Some commentaries suggest that the purpose of determining the size of a garden bed’s boundaries was to determine how much space must be left between the garden beds, to avoid prohibited mixtures of diverse kinds of seeds (Me’iri). In the Mishna in tractate Kilayim, there is a suggestion that one could plant on the boundary itself, necessitating the determination of its size. As for the halakha, some authorities rule that the boundary of a garden bed must be one handbreadth wide (Tosafot) with an additional two handbreadths between garden beds.
Others state that a single handbreadth between garden beds is sufficient (Me’iri).
There were alternative suggestions on how to best plant suggested by the amora’im.
Rav Kahana said that Rabbi Yoḥanan said: One who wishes to fill his entire garden with vegetables and does not want to distance the rows of seeds from one another may make a garden bed that is six by six handbreadths and make five circles inside it. He plants different species in the different circles and fills its corners with whatever additional species that he wants.
According to the Rambam, one is not restricted to five species but can plant up to nine: Five kinds of plants in each of the circles and another four in the corners. The Ra’avad, however, explains that one is permitted to make five rows of five circles, each with a diameter of one handbreadth, along the length of the garden bed, for a total of twenty-five circles in the garden bed.