Shalom kavod haRav. We bought a couple of citrus trees some years ago without paying proper attention to the fact that they are grafted (we’re living in Israel). They are lemon and kumquat trees. The bark of the rootstock below the grafting point looks slightly different from the bark of the upper tree, but it does also look like some type of citrus. It is no longer possible to get clear information about the rootstocks, and if the grafting was done in a halachically permitted way within one species or if there is a problem with kilyaim. Is it permitted to keep the trees? Is it permitted to plant them into the ground (they are in containers now) and to water them, or do they have to be destroyed or abandoned because of the doubt that they might be kilayim? In addition, we have another tree (orange) where we could trace back the place it was bought from, and one of the people from the place told me over the phone that the tree was grafted onto "some kind of other orange tree, and that there is no need to worry about kilayim". Is it possible to rely on such a statement? What about planting and watering that tree? Thank you very much.
Shalom, After checking with a citrus specialist, it turns out that citrus fruit can only be grafted upon other citrus bases. According to the Chazon Ish, all citrus fruits are considered one species, thus there are no problem regarding grafting with each other. In addition, most fruit tree nurseries in Israel graft according to the halacha, otherwise the rabbinical supervisors won't let them sell to any of the orchards which market to Tnuva (which has almost a monopoly on fruit). In short, although one should check out the "history" of a tree before buying it, in your situation, there’s no problem to plant and enjoy the fruit- and as a matter of fact, it’s even a mitzvah to plant, especially fruit trees, in the Land of Israel (Mitzvat Yishuv HaAretz)! With Love of Israel, Rav Ari Shvat