Halakhah for Kiddushin 77:10

To not sow seeds of forbidden mixtures and not graft in any place in the Land: To not sow two species of seed, such as wheat and barley or fava beans and peas, together - only in the Land of Israel - as it is stated (Leviticus 19:19), "your field shall you not sow [with] a forbidden mixture." And the explanation comes about it (Kiddushin 39a) that the verse is speaking about a field that we have in the Land.

And the principle that comes out in our hands from their words, may their memory be blessed, regarding forbidden mixtures of seeds is that anytime that there is a proper distance between the two types - and that is one and a half handbreadths, as we said - even if the leaves are mixed up, we do not concern ourselves about them; and likewise, anytime they appear separated one from the other, such that the leaves of one garden bed lean to one side and the leaves of the garden bed adjacent to it [lean] to another side - even though they are feeding one from the other - we do not concern ourselves with their feeding. As the Torah [only] paid heed to both of them together - that they feed one from the other and that their feeding be seen clearly by the eyes of the onlookers. And about what are these words speaking, that it needs distancing, or something that separates? When he sowed in his [own] field. But if his field is planted with wheat, it is permitted for his fellow to sow barley adjacent to it; as it is stated, "your field shall you not sow [with] a forbidden mixture" - meaning to say, specifically, your field - as it was not written, "the land shall you not sow [with] a forbidden mixture." And they, may their memory be blessed, also learned (Kiddushin 39a) [from] "your field," to say that it is only in the Land that the prohibition of forbidden mixtures of seeds is practiced, but not outside of the Land. [This is the case,] even though they did not say thus regarding the grafting of trees, which is also derived from "your field," but which is rather practiced in every place - and as Shmuel said [there] in the first chapter of Kiddushin, since he compares the grafting of trees to the mating of beasts which is practiced in every place. They, may their memory be blessed have already resolved [this difficulty] there in Kiddushin. And if you desire, my son, to know [their resolution], see it there. And the rest of its details are in Tractate Kilayim.

And [it] is practiced in every place and at all times by males and females. And Rambam, may his memory be blessed, wrote (Sefer HaMitzvot LaRambam, Mitzvot Lo Taaseh 192) and this is his language: "As the prohibition of orlah outside of the Land is a law of Moshe from Sinai. However the language of the Torah is that it is only in the Land." To here [are his words]. Since in the Torah it is stated explicitly, "And when you come to the land and plant" - which implies specifically in the Land. And explicitly did they, may their memory be blessed, say (Kiddushin 39a) that so was it said about it [that] the law of Moshe from Sinai [is that] its definite is forbidden, but its doubt is permitted - meaning to say that its prohibition is not like the other prohibitions in the Torah, such that any time we encounter a doubt in a thing that is of Torah writ, we should forbid it from the doubt; since it is established for us that [in a case of] doubt about a Torah law, it is forbidden. And likewise have we elucidated with the good commentaries that [a case of] doubt about a law of Moshe from Sinai [should be decided] towards stringency. But about the prohibition of orlah, we have received [from the tradition] that it was specifically said to Moshe that its doubt is permitted. And since this is so, that the prohibition of orlah does not rest at all [upon it] in a doubt, an Israelite that has a tree that is orlah in his garden is not at all required to inform his fellow that comes to eat from it, that it is orlah. And regarding this, we have found in the Gemara that they said (Kiddushin 39a), "It is a doubt to me and I will eat" - meaning to say that any time that a person does not know with certainty that it is orlah, it is permitted for him to eat from it. And one who transgresses it and eats a kazayit from fruits of a tree in its years of orlah - or even from that which protects the fruit, [in the case] that it was known as that which was forbidden with it - is liable for lashes.