It is forbidden to graft two types of fruit tree together. An orange and a tangerine are different fruits. It is forbidden to say to Non-Jew to do it. So since he asked you should say no. If your gardener came one day and you see him doing it anyway you don’t have to stop him.
Explanation:
The Gemara in Kiddushin (39a) writes:
The Gemara is clear that just as Kilayim (forbidden mixtures ) of animals are forbidden even in Chutz Laaretz, so too Kilayim of trees are forbidden n Chutz Laaretz.
What is the prohibition of Kilayim by trees?
Rashi explains that grafting trees is when you take two different types of fruits. The Meiri explains grafting is when one takes a bracha of a nut tree and grafts on a fig tree. Or a fruit onto a non-fruit tree or by attaching a tree branch with a vegetable like broccoli or planting a shoot in a watermelon, are all forbidden.
Planting a fruit seed with a vegetable seed or two types of fruit seed sis not forbidden. Kilayim by a tree is only grafting however if it is two types of one fruit ,like two types of pears art no forbidden.
We see that prohibition of grafting trees is derived from the prohibition of interbreeding animals. Therefore It is forbidden from the Torah in Chutz Laaretz as well and not just on Eretz Yisrael. So rules the Rambam in Hilchot Kilayim 1:5 : Kilayim of trees are derived from the passuk of “Your field you may not plant mixed.” When is it grafting? If he took a branch of an apple tree stuck into an Etrog tree or an Etrog into an apple he gets Malkot in Eretz Yisrael or in Chutz Laaretz. So too one who grafts a vegetable with a tree or the opposite. R Chaim Kanievsky in Derech Emunah explains the prohibition of grafting a branch of one type with another or putting a small branch into a fruit or a fruit into a tree or a fruit into fruit, they are all forbidden from the Torah.
In our case its forbidden to graft a tangerine tree with an orange tree since they are considered two different types. The second question is a non-Jew does it what is this halacha.
The Rambam in the next halacha writes it is forbidden for Yisroel to let a Non-Jew graft his tree Kilayim. Ina previous Halacha the Rambam says (Halacha 3): it is forbidden to pant Kilayim from a Non- Jew but is permitted tell a Goy to plant Kilayei Zeraim.
There seems to be a contradiction, since here he says it is permitted to the Goy to plant Kilayim for him, but by tree he says it is forbidden.
The Radbaz writes that which the Rambam says to a Non-Jew to plant Kilayei Zeraim it means that it is permitted to say o a Non-Jew to plant the Kilayei Zeraim in the Goy’s ground which is permitted in Yisrael. That which the Rambam said it is forbidden to ask a Non-Jew to graft them is when the Goy is grafting into the Jew’s trees. Why did the Rambam go out of his way to tell us this, that one may tell a Goy to plant kilayim in his own land? The Taz (Yoreh Deah 296:1) explains One could have thought that we are of the opinion that a Goy who buys land in Eretz Yisrael does not exempt the land from al the Halachot involved in it. Therefore when you tell him it is as if he is planting in the Jew’s land. The Rambam comes and tells you that we don’t say that and it is permitted..
However according to the Rambam in Hilchot Melachim 10:6 that a Non-Jew is also commanded not to do Kilayim of animals and grafting trees, therefore it is forbidden to let a Goy graft in a Jew’s own field because of Lifnei Iver, we are causing him to do an aveirah. He shod stop him. So writes R’ Chaim Kaneivsky. He adds However most Rishonim argue on the Rambam and Bnei Noach are not prohibited in Kilayim at all. To tell a goy to do it for you is forbidden from the Rabbis because it is ‘Amirah La’akum”, telling a goy to do an Issur for you which is forbidden in all halachot. The Chazon Ish follows most of the other opinions not the Rambam.
In our case it is forbidden to tell the gardener to graft the trees together. However if he did without you asking him you do have to stop him. However the Derech Emunah quote the Chazon Ish that one who grafts together two types of branches which are detached and plant them together is it considered grafting and one who does such a thing and plants it in his garden transgresses a prohibition. Even if you plant them with their dirt clumps, they can’t stay for a long time with just the clumps and planting them the will live long, ti is forbidden.
