Planting mixture of seeds is assur only when they are viewed as growing together. The mishna discusses the scenario of a 6x6 tefach box where 4 different types of seeds can be planted along each edge and then a 5th type of seed right in the middle. The seeds on the edges don’t look mixed bc they run perpendicular, and the middle seed isn’t mixed with the sides bc it’s distanced 3 tefachim from each side. With 3 tefach distance the rabbis know it won’t nourish from the ground together.

Where’d the rabbis learn about these details of nourishment? They learned it from the the Chorite ppl who were such expert sub agriculture they could smell and taste the soil to figure out what to plant.

When the mishna spoke of the 6x6 patch, it was not including the walkway around it. Generally, a normal patch has a 1x1 walkway surrounding the patch to water the vegetables.

Acc to rav, our mishna is only discussing a case where the patch is not surrounded by other planted patches. In that case, the four seeds can be planted to the edge with no concern. If there are surrounding patches, it doesn’t work bc the seeds from the neighboring patches are too close together and are perceived like one big planting. Shmuel disagrees. He holds one can stagger the edges and ensure that proper distance is maintained between one patch and the next.

Since kilayim is all about the perception of mixture, there’s a rule of ראש תור. If the tip from a big field protrudes into another location with different spices, it’s not kilayim bc it’s easy to see that the tip is just an extension from the bigger field.

One can plant different types of seeds in a field parallel to each other if they are planted in pairs. If they are planted as single rows, they have harder time sticking out independently so it’s kilayim. Acc to one opinion, this is only by species that have long vines that can get intermingled.

Another method of planting dif species in a 6x6 square is by planting in a circular 5 space and then having dif species on the edges. The difference in shape helps keep it distinct.