3,043. How Far to Space Two Different Types of Grain

Hilchos Kilayim 3:8

There are a lot of different measures when it comes to how far one must distance plants in order to make sure they remain distinct; it all depends on the size of the field being planted, how prolific the leaves of the plants are, and how far the branches extend.

Hilchos Kilayim 3:9

Pursuant to the previous halacha, let’s say that someone planted one species of grain in his field and he wanted to plant a different species of grain in an adjacent field. In such a case, he must separate between them an area sufficient to plant a quarter-kav of seed (about a third of a liter). This is an area approximately 10.2 cubits by 10.2 cubits (approximately 232 square feet). This is the case regardless of whether the empty space stops in the middle of the fields or runs along their sides. If the space between them is smaller than this, it is prohibited to plant there but one is not liable to the penalty of lashes unless the plants are within six handbreadths of one another (about 18 inches).